Micro Lab 1

Match the staining procedure with its description.

Gram stain- A stain that can differentiate between cells that have thick or thin layer of peptidoglycan in their cell waslls Acid-fast stain- A stain that would be appropriate for cells that contain mycolic acid in their cell walls Capsule stain- A stain that enables you to efectively visualize a bacterium's glycocalyx

What is used as the mordant in the Gram staining technique?

Gram's iodine

What type of bacterial cell wall us composed of a thin layer of peptidoglycan and an outer membrane?

Gram-negative

What might happen if you omitted the safranin step while performing the Gram stain on a mixed culture of gram-positive and gram-negative cells?

Gram-negative organisms might not be visible

If you forget to use the decolorizer, which cell type(s) will appear purple?

Gram-positive Gram-negative

What outcome could be expected if you forgot the crystal violet step while performing a Gram stain?

Gram-positive and gram-negative organisms would stain pink

If safranin was omitted from the endospore stain, what color would the endospores appear?

Green

In this image, the endospores are _____ in color.

Green (The green structures within the pink-red vegetative cells are the endospores)

Measuring absorbance in the indirect spectrophotometer method can allow one to determine if cells are _______.

Growing

In order to ensure that dye penetrates the spore coat and stains the endospore, which of the following is needed?

Heat

When should heat fixation take place during the capsular stain?

Heat fixation is not required in the capsular stain

Which of the following describe the correct sequence of the Gram stain procedure?

Heat-fixed slide; Use of crystal violet, iodine, decolorizer, and safranin

Which of the following is true regarding proper heat fixation?

Heating too briefly may result in bacteria not adhering to the slide (Not heating long enough will not allow the bacteria to adhere to the slide and they may be rinsed off during staining)

The individual slender filamentous structures typical of molds are called ________.

Hyphae

The strand-like structures in this image of Aspergillus are ______, and the dark ball-like structures contain the ____ used for reproduction of this organism.

Hyphae; spores

Why is it important to rinse the cuvette with water?

If the cuvette is not rinsed, there will still be remains from the previous sample that would affect the following absorbance reading

Which image gives you the best view of the penicillium structures?

Image A

Match the plate images with the method used to prepare each plate.

Image A- Quadrant streak plate method Image B- Pour plate method Image C- Serial dilution and plating method

You are looking at three images taken under a brightfield microscope using all of the objectives except the oil immersion lens. Which image represents the one you would likely see when using the 10x objective?

Image C (Image C represents a magnification level between the other two images, and the 10x objective provides a level of magnification between the 4x and 40x objectives

You have been examining an object under low power and have placed a drop of immersion oil on the slide and rotated the high power (40x) lens into place. You are having difficulty sharpening your image using the fine focus adjustment knob. What is the most likely explanation?

Immersion oil cannot be used with the high power (40x) objective lens.

Why is the image blurred when the 100x objective is used?

Immersion oil has not been added to the slide

What should be adjusted first for better viewing of this slide? (Dark hard to see)

Increase the light intensity

Which stain is used to stain the background in the capsule stain?

India ink or nigrosin

What is the consequence of not using a lens with adequate resolving power when visualizing a stained smear of Staphylococcus aureus?

Individual cocci will not be visualized

A successful streak plate provides ______ colonies on the top of the agar which may be used for further study.

Isolated

When subculturing, ______ colonies should be transferred to a nutrient agar slant.

Isolated

When subculturing to make a pure culture, what bacteria should be used?

Isolated bacterial colonies

Separating a complex culture of bacteria into distinct colonies on solid media is achieved using a(n) ______ technique.

Isolation

You spread an inoculum of mixed bacteria across an agar plate so that individual cells will give rise to dispersed bacterial colonies. This process is specifically referred to as _____.

Isolation

What is the advantage of using the standard plate count over other enumeration methods when determining the safety of a food or water sample?

It provides a court of only living bacteria which represent the safety concern (The standard plate count only records living bacteria that grow on a solid medium)

You are viewing a slide with cells that have a distorted shape and do not appear to be arranged in any specific manner. What may have occurred during the preparation of this slide?

It was excessively heat fixed

You accidentally drop stack of agar plates as you take them to the lab bench for observation. A few lids were separated from the plates. You may still be able to evaluate your results if the plates were ______.

Labeled on the bottom

What should be used to clean the slide and lens after viewing under oil immersion?

Lens paper

Letter B represents what phase of the growth curve?

Log phase (Letter B indicates a dramatic increase in population growth which occurs during the log (exponential) phase)

When streaking a plate, the inoculating ______ is the best instrument to use to prevent tearing the agar surface.

Loop

Did the student correctly handle the glass culture tubes?

No (The student did not flame the mouth of the tube when the cap was removed or replaced.)

When a loop that is too hot is used to make a subculture to a slant, what will the growth pattern be on the tube after incubation?

No growth

Can you be certain that you made a successful transfer if your sterile broth is turbid after incubation?

No, the broth will be turbid if it is correctly inoculated, but also if it was contaminated during the inoculation procedure

The slide depicts bacteria that were properly stained using the acid-fast staining technique. The bacteria appears to be ____.

Non-acid-fast

This slide depicts a mixed culture of bacteria that were properly stained using the acid-fast stain. Which are more numerous, acid-fast or non-acid-fast cells?

Non-acid-fast

What part(s) of the microscope were moved?

None

Serial dilution and the standard plate count (SPC) method are used to determine the _______ of organisms present in a bacterial culture.

Number

When determining if a patient has a bladder infection, it is critical to calculate the ____ of bacteria in the urine.

Number

Which type of media is used in the pour-plate method?

Nutrient agar pours

The _____ lenses further magnify the image produced by the objective lens.

Ocular

How many different *types* (species) of organisms are there in a pure culture?

One

How many bacterial cells were required to start a single colony of growth on a plate?

One (Only one cell is needed to start a colony on a plate. If more than one cell is present there is no guarantee the cells are of the same bacterial type.)

During the steps of the streak plate method, the bacterial culture is only added to the plate _____ time(s).

One (The goal of making a streak plate is to end up with isolated colonies, so only one sample if bacterial culture is added to the plate in quadrant one. Then the sample is diluted from one quadrant to the next)

A pure culture contains ____________.

One type of microorganism

What is the correct way to open an agar plate while removing a sample or inoculating the plate?

Open one side of the lid diagonally off the plate

If you decolorize for more than 30 seconds, gram-positive organisms will most likely appear ____ in color.

Pink

If you omit the Gram's iodine step while performing the Gram stain, gram-positive cells will most likely be ____ in color.

Pink

After preparing a wet mount of the vaginal discharge, the slide is placed on the ______ of the microscope for viewing.

Stage

You are viewing this slide of Penicillium under the 10x objective lens. What part of the microscope should be used before shifting to the 40x objective lens?

Stage adjustment knobs (It is important to center the object you are viewing in the field before switching to a higher magnification or the specimen may disappear from the field of view.

In order to enhance the contrast of a slide preparation, the physician could have _______ the specimen before viewing.

Stained

Which occurs first in the endospore stain?

Staining the endospore

The _____ plate count (SPC) method involves diluting 1.0m of bacterial culture into a series of water blanks, and then taking a sample from the water blanks to add empty petri plates which will be filled with melted agar.

Standard

Select the term which best describes the morphology and arrangement of this organism.

Staphylococcus

The organism in the slide exhibit a cellular arrangement known as __________.

Staphylococcus

The rate of cell division and cell death are relatively balanced during which phase of the growth curve?

Stationary phase

Staining techniques do NOT provide information on which of the following structures?

Ribosomes (Ribosomes are too small to be identified using basic staining techniques)

What changes was likely made to the microscope between the image on the left and the image on the right?

Rotation of objectives

The name of the counterstain, or secondary stain, typically used in the Gram stain technique is _______.

Safranin

______ is used to stain the vegetative cells in the endospore staining procedure.

Safranin

If leaving an objective lens over the stage when storing the microscope, which objective lens should be placed over the stage?

Scanning (4X)

In a differential staining technique, the stain that is used after the decolorization step is called the counterstain, or ____ stain.

Secondary

Which method gives easily countable plates and the ability to calculate the bacterial density in the originally undiluted culture?

Serial dilution and plating

In the video, what major error did Jeanne make when transferring the culture?

She forgot to sterilize the loop before and after transfer

Which of the following provides a quick and effective method used to visualize and determine bacterial morphology and arrangement?

Simple stain

Match the general type of staining method with its description.

Simple stain- Uses only a single dye to color the cells Differential stain- Uses two dyes to discriminate between cell types or structures Structural stain- Assists in the observation of structures external to the cell wall

A glass tube of solid medium with an angled surface is referred to as a ________.

Slant

Which slant(s) depict correctly inoculated slants?

Slant A Slant C

To prepare a ______, a sample of bacteria is taken from a culture and spread onto a clean microscope slide.

Smear

If the agar is allowed to cool properly, the agar surface will be _____.

Smooth

Which of the following accurately describes a successful pour plate?

Smooth agar surface with colonies on the surface and within the agar

Which of the following techniques results in isolated colonies found only in some areas on the agar surface?

Streak Plate Technique

Absorbance or optical density is measured using a _____.

Spectrophotometer

Which major piece of laboratory equipment is used when measuring absorbance?

Spectrophotometer

Select the term that best describes the morphology of this organism.

Spirochaete

You are observing Klebsiella pneumoniae on a slide that has been stained using the capsular staining method; however, you do not see capsules surrounding the cells as you expected. What is the likely reason for this?

The slide was heat fixed

What is the most likely reason for the poor appearance of the bacteria on this slide?

The slide was heat fixed for too long (An appropriate amount of bacteria was used, but the slide was heat fixed for too long, causing destruction of the cells)

When studying population growth curves with a spectrophotometer, why is it unlikely that you will see the typical steep decrease of the curve during the death phase?

The spectrophotometer measures turbidity of the tube, which is influenced by both living and dead cells

What is thought to cause gram-positive cells to retain the primary stain and the mordant complex whereas gram-negative cells are decolorized?

The thickness of the peptidoglycan layer

Which of the following would indicate that contamination had occurred in a transfer from an E. coli slant to a sterile slant?

There is red and white growth on the surface of the slant (A mixture of two different colony types would indicate contamination. A pure culture of E. coli would not produce two different colony types.)

The cloudy growth seen in a broth culture is referred to as the ______ of the culture.

Turbidity

Because microorganisms are present nearly everywhere at the same time, we can describe them as _____.

Ubiquitous

This image represents a(n) ________.

Unicellular fungi (This image is a yeast with characteristic ovoid-shaped cells, and therefore, it represents a unicellular fungi

The inoculating loop should be placed in the hottest part of the flame _____.

Until the loop is red-hot

How do you smear a bacterial colony onto the microscope slide?

Using the loop, you disperse the bacteria into the water drop on the microscope slide

How do you smear a bacterial culture onto the microscope glass slide?

Using the loop, you spread the bacteria onto the center if the microscope slide

What is the BEST way to prevent menigococcal meningitis in laboratory workers like Jeanne?

Vaccination

This was observed on the wet mount of the vaginal discharge. The most likely diagnosis is ____.

Vaginal candidiasis (yeast infection)

Which specimen might provide information leading to diagnosis of the cause for the current symptoms?

Vaginal swab

A(n) )_______ is a metabolically active and growing cell.

Vegetative cell

Bacterial cells that are curved rods or comma-shaped are called _____ whereas helical bacteria are referred to as spirilla or spirochetes.

Vibrio

Which of the following microorganisms are you likely to view in a sample of pond water?

-Algae -Cyanobacteria -Protozoa

Which of the following groups include microscopic organisms?

-Algae -Fungi -Bacteria -Protozoa

What characteristics are common to all algae?

-Algae possess cell walls made of cellulose. -Algae possess chlorophyll and other photosynthetic pigments inside of chloroplasts.

Select the statements that correctly describe algae.

-Algal cells are eukaryotic -Algae are photosynthetic

Which of the following are necessary for a successful streak plate?

-Applying the loop lightly and not tearing the media -Flaming the loop between each streak quadrant -Rotating the plate between each streak

Which of these domains include prokaryotic microorganisms?

-Bacteria -Archaea

Excessive heating during the fixation stage of preparing a smear can lead to which of the following outcomes upon staining?

-Bacterial cells may show altered morphology -Bacterial arrangements may be disturbed

Which of the following are needed when performing a serial dilution for the standard plate count method?

-Bacterial culture -Nutrient agar -Petri plates -Pipets -Water blanks

When should the inoculating loop be sterilized in the Bunsen burner?

-Before the inoculum is picked up from culture tube -After the transfer is complete

In the video, Jeanne was working on an open benchtop. What safety equipment should she have utilized for this testing?

-Biosafety cabinet

Which of the following represents a disadvantage of streak plate method? Click all that apply.

-Cannot enumerate bacteria after incubation -Requires practice to master the skill of inoculating the plate

Excessive heat fixation can cause damage to which of the following structures, lowering the quality of the stained preparation?

-Cell wall -Capsule -Cell membrane

Which of the following could be determined through simple staining of a microbial smear?

-Cellular arrangement -Cellular morphology

Which of the following can be determined by observing bacteria that have been stained though a light microscope?

-Cellular morphology -Cellular arrangement

Which of these microorganisms have you observed?

-Coelastrum -Eugiena -Cocconeis

Which of the following terms are used to describe the morphology of algae?

-Colonial -Filamentous -Unicellular

What characteristics of bacteria/fungi are observable by exposing, incubating, and examining the growth on agar plates?

-Color of colonies -Ability to be cultured on general purpose media -Colony morphology

Select the characteristics of this organism. (Aspergillus, a fungi)

-Contains a cell wall made of chitin -Heterotrophic -Eukaryotic

Which of the following are used by protozoa for motility?

-Cytoplasmic extensions called pseudopods -Flagella -Cilia

Which of the following represent consequences of incorrect performance of the decolorization step?

-Decolorizing for too long: removal of carbolfuchsin (primary stain) from all cells -Decolorizing too briefly: false positive results -Decolorizing for too long: false negative results

What simple steps could be taken to improve contrast for viewing this microorganism?

-Decrease the light intensity -Stain the microorganism

Endospores are difficult to stain die to which of the following?

-Endospores have a thick spore coat -Endospores exclude dye

Which of the following are correct ways to label the organism found in a culture? (Check all that apply).

-Escherichia coli -E. coli

Which of the following stains require heat fixation?

-Gram stain -Acid-fast stain -Endospore stain -Simple stain

Which of the following correctly describe how the Gram stain works to color different types of cells?

-Gram-negative cells are decolorized and stained by the pink/red secondary stain -Gram-positive cells retain the purple dye-mordant complex because of their thick layer of peptidoglycan

Indicate which of the following are classified as algae.

-Green algae -Brown algae -Dinoflagellates -Diatoms

If organisms are washing off of the slide during rinsing of the stain, which step(s) in the smear preparation may have been excluded?

-Heat fixation (if heat fixation did not occur, it is not likely that the cells will adhere to the slide) -Air drying (If the smear was not air dried, it is not likely that the microorganisms would adhere to the slide during heat fixation

Staining is a commonly used microbiological technique that is used for which of the following?

-Identification of some bacterial structures -Visualization/ Differentiation of microorganisms

Microorganisms may be found in which of the following locations?

-In the air in the laboratory -On your hands -On a disinfected bench top (wiping down the bench with disinfectant may remove or destroy the less resistant microbes, but it does not result in a sterile benchtop so some resistant microorganisms may still be present.)

Which of the following are situations where the standard plate count could result in an underestimate of bacterial numbers?

-You inoculate and incubate the plates in anaerobic conditions -You accidentally use a selective medium instead of a general-purpose medium for plating the dilutions -You forget to put the plates into the incubator after plating

You notice a strange fuzzy white colony on a plate of yellow Micrococcus luteus colonies after incubation. What may have occurred during the transfer to the plate?

-You may have left the plate completely uncovered for too long during the transfer -You may not have adequately sterilized the transfer tool

The use of __1___ technique is important in obtaining __2____ cultures, those that contain only one type of microorganism.

1- Aseptic 2- Pure

(1)____ are long appendages for motility, usually singular or few in number whereas (2)______ are short appendages used for motility, usually very numerous.

1- Flagella 2- Cilia

Molds produce microscopic filament-like structures called __1______ that become intertwined to form a macroscopically visible mass called a ___2_____.

1- Hyphae 2- Mycelium

Gram-____1____ cell walls contain a thin layer of peptidoglycan whereas Gram-____2___ cell walls contain a thick layer of peptidoglycan.

1- Negative 2- Positive

__1__ plates allow you to observe colonies under the surface of the agar, whereas __2___ plates and serial dilution plates only show surface growth.

1- Pour 2- Streak

Gram-negative cells appear ___1__ after Gram staining whereas gram-positive cells appear __2____.

1- Red 2- Purple

The type of stain designed to show differences between various organisms or cellular structures is referred to as a/an ____1____ stain, whereas a ____2_____ stain uses only one dye to stain all cell types.

1- differential 2- simple

The two main transfer tools that are used when inoculating bacteria from one culture medium to another are called an inoculating ____1____ and an inoculating ___2_____.

1-Loop 2-Needle

Place the steps of the endospore stain in the correct sequence.

1. Apply malachite green to smear 2. Cover smear with small piece of paper towel 3. Steam over water bath 4. Rinse 5. Apply safranin to smear 6. Rinse and blot dry

Place these reagents in the proper order of their use in the Gram staining technique.

1. Crystal violet 2. Gram's iodine 3. Decolorizer 4. Sarfranin

Based on the graph, put these organisms in order of their speed of population growth starting with the fastest growing bacterial species.

1. Escherichia coli 2. Citrobacter freundii 3. Staphylococcus aureus

After subculturing one colony on a mixed isolation plate to a sterile slant, what should be the result?

A slant with one type of bacteria growing

When subculturing a bacteria species, you should sample ____.

A small portion of an individual colony

The low pelvic pressure and vaginal irritation and discharge suggest ______.

A vaginal infection

Looking at this data, match the areas of the graph with the correct growth phase.

A- Lag phase B- Log phase C- Stationary phase

After using uninoculated nutrient broth to blank the spectrophotometer, the blank must be removed and a cuvette with bacterial culture added. The cover is closed, and the _______ or optical density is read.

Absorbance

Which feature of an enzyme is the "most" unique?

Active site

You have successfully focused on an object with the 10x and 40x objective lenses. You have rotated the 100x objective lens into position but are unable to obtain a sharp image by rotating the fine focus adjustment knob. Which of the following is most likely to correct this problem?

Add a drop of immersion oil before rotating the 100x lens into position

What quick adjustment would increase the viewing quality of the specimen on this slide? (blurry)

Adjust the distance between the occulars

Slants are solid because they contain ____, which makes them solid at temperatures below 46 degrees Celsius.

Agar

Heat fixation should take place right after which step in a smear preparation?

Air drying of smeared bacterial cells

The organism seen here is a(n) _______.

Algae

Which of the following is not a common staining method used for visualization of bacteria?

All of the above are commonly used (simple, negative, capsule, endospore, acid-fast)

What type drug might be used to treat this infection?

Antifungal

If carbolfuchsin was omitted from the acid-fast stain, what color would non-acid-fast cells appear?

Blue

Under what circumstances would you use the coarse focus adjustment knob?

Bringing a specimen into view under low power

Which image shows a correctly performed capsular stain?

C

Which of the following illustrates a properly stained capsular stain?

C

Which of the following streak plate diagrams shows the correct pattern for a quadrant streak plate method?

C

Which of the image is representative of a correctly made pour plate?

C

Which of the images depict a slide that was prepared from the most appropriate amount of microbial material?

C

Which of the images shows a simple stained slide that was prepared from the appropriate amount of microbial material?

C

Which set of serial dillution plates shows the possibility that the original bacterial culture was not adequately diluted?

C

Preparation of a wet mount is a lengthy process.

False (A wet mount can very quickly be prepared with minimal equipment)

It is necessary to use a colony counter when completing a standard plate count.

False (Actually, you can use a colony counter when completing a standard plate count)

Just by looking at a broth transfer, one can tell if contamination has occurred.

False (Growth is observed in a broth as turbidity, or cloudiness, but one cannot tell which organisms are present just by looking at the tube.)

Separated bacterial colonies are observable in broth cultures.

False (In broths, the growth appears as turbidity (cloudiness) but individual colonies are not observed.)

At four hours, you can already easily observe the growth of inoculated bacteria.

False (In most cases, colonies have not yet grown to a size that is easily observable on the surface of the agar after only four hours)

Prokaryotic cells are generally larger than eukaryotic cells.

False (Most prokaryotic cells are 0.5-10 um in size, whereas eukaryotic cells generally are in the 10 um-100 um size range.)

The simple stain provides enough information about a microbe to clearly identify its species.

False (The simple stain does allow for the visualization of shape and arrangement, but cannot be used for specific identification of a species. For example, all species of Staphylococcus would look the same under the microscope after simple staining)

The term "ubiquitous" refers to the fact that it is impossible for an environment to be free of bacterial life.

False (Ubiquitous refers to the fact that bacteria are present nearly everywhere. However, it is possible that some environments are sterile, meaning they are free from all microbial life)

Due to their small size, all prokaryotes must be visualized using electron microscopy.

False (most prokaryotes can be visualized using *brightfield* microscopy by enhancing their contrast through staining techniques

By looking at colony growth on a general-purpose medium, you can usually tell what species of bacteria are growing on the plate.

False (Determining the exact species of a bacterium requires further work including microscopic examination and/or physiological testing.)

All algae are unicellular.

False (Many algae are unicellular, but others are multicellular forming filaments or colonies.

All fungi are multicellular organisms.

False (Yeast are unicellular forms of fungi.)

When using the higher magnification lenses (40X and 100X), only the ______ focus adjustment knob should be used.

Fine

This protozoa would be classified as a(an) _____________.

Flagellate

What did the student forget to do in this transfer?

Flame the mouth of the culture tube

How do fungi obtain their energy and nutrients?

Fungi absorb their nutrients

Which of the following would have been the BEST way for Jeanne to prevent this infection?

Getting her meningococcal vaccination

The _____ stain provides critical information about the peptidoglycan structure of the cell wall.

Gram

The capsule staining technique begins with a(n) ______ stain.

Negative

Which components contribute to the structure of ATP?

-Adenine -Ribose -Phosphate

The purpose of heat fixation is to ______.

-Adhere the organisms to the slide -Inactivate microorganisms placed on the slide

The lab bench is treated with a disinfectant at what points in the lab exercise?

-After work is finished -Before work begins

A smear preparation that is too light may result in which of the following?

-Inability to distinguish individual cell morphology (A smear that is too light will have too few cells in the smear preparation, making it difficult to view cells to determine their morphology) -Difficulty locating cells to observe (A smear that is too light, will have too few cells in the smear preparation, making it difficult to find cells using the microscope)

What tools are typically used for transferring small amounts of bacteria from one culture medium to another?

-Inoculating loop -Inoculating needle

A simple stain would be ineffective for observing which of the following organisms?

-Intracellular pathogens -Viruses

Which of the following is true for pour plating but not for quadrant streak plating?

-Isolated colonies form within the agar plate -It requires the use of multiple tubes and plates

Why is agar used in the medium when conducting the pour plate technique?

-It can be inoculated in a liquid form at temperatures that are not harmful to most bacterial life -It solidifies at room temperature so that colonies can form on the solid medium

What are the advantages of using a colony counter when conducting a standard plate count?

-It has magnifying glass that can be used to locate and count smaller colonies -It automatically adds to the colony count each time you press on the glass -It has grid lines to help you keep track of which colonies have already been counted

Which of the following are diseases caused by an acid-fast bacterium?

-Leprosy -TB

The acid-fast cell wall contains large amounts of mycolic acid. This glycolipid ____.

-Makes the cell wall resistant to decolorization with acid-alcohol -Makes the cell wall less permeable to chemicals

The major approaches to characterizing microorganisms include which four of the following?

-Microscopic -Biochemical -Macroscopic -Genetic

Which of the following clinically important organisms are considered acid-fast?

-Mycobacterium tuberculosis -Mycobacterium leprae

The acid-fast cell wall contains large amounts of mycolic acid. Which of the following can be attributed to the presence of mycolic acid?

-Mycolic acid makes the cells more difficult to stain -Chemicals cannot readily penetrate the cell wall of these cells

Pour plating can be used for which of the following?

-Obtaining isolated colonies for making pure cultures -Determining bacterial numbers in a sample

When do colonies grow in pour plates?

-On the agar surface -Within the agar

Why are plates labeled on the bottom of the agar plate?

-Plates are stored on their lids so this makes it easy to see labels even when on the shelf of the incubator. -The information about the plate is still available even if the lid becomes separated from the bottom. -Labeling the bottom allows labeling of different sections of the plate. The lid might rotate and labeles would not match the sections.

Which of the following can occur due to using excessive material to create a smear preparation?

-Poorly stained slide -Inability to distinguish the morphology and arrangement of cells -Inability to remove excess stain on slide

Which of the following are terms used to describe the *colored* dyes applied in the Gram staining technique?

-Primary stain -Counterstain (Secondary stain)

Which of the following are functions of the bacterial capsule?

-Protection -Adherence -Interaction with host

Select the statements that accurately describe protozoa.

-Protozoa are heterotrophic and ingest their food. -Protozoa are most often classified on the basis of motility. -Protozoa have a eukaryotic cell structure.

Before bacteria from a solid culture are applied to a slide, a drop of sterile water is typically added to the slide in order to ______.

-Reduce the tendency of the bacteria to stick together (The water allows the bacteria to be suspended and therefore more easily dispersed) -Help the bacteria spread easily

Which are the three most important factors that determine the quality and clarity of a microscope image?

-Resolving power -Magnification -Contrast

What isolation methods could be used to determine the number of bacteria in a specimen?

-Serial dilution and plating -Pour plating

Jeanne did not follow appropriates safety measures when it came to protecting herself. Where did she go wrong?

-She didn't wash her hands at the end of the work -She didn't wear gloves

In the video, what did Jeanne do right when transferring the culture?

-She kept the cap in her hand -She flamed the mouth of the culture tubes when removing and replacing the cap

Which types of sterile media are solid in nature?

-Slants -Agar plates

Which three of the following terms all refer to a similar structure?

-Slime layer -Capsule -Glycocalyx

Which of the following could contribute to a poorly stained slide?

-Stain was rinsed too soon -Bacteria were not "fixed" to the slide -Too many cells in smear preparation

Which of the following environments would likely be free of microbial life?

-Sterilized field in operating room -Inside properly canned food

What factors can greatly impact the growth of bacteria in an environment or on a particular object?

-Surface material and texture -Temperature -Moisture -pH -Oxygen availability

What cautions should be taken when the pour plates are placed in the incubator?

-The agar plates should be allowed to solidify at room temperature before moving them to the incubator -The plates should be placed in the incubator upside down

What is an inoculum?

A sample of bacteria transferred from one medium to another

What might be the result of not allowing a slide to air dry sufficiently prior to heat fixation?

-The bacteria could be aerosolized (Small amounts of remaining liquid on the slide could be vaporized when heat fixing the sample. This in turn could cause some bacteria to be aerosolized and potentially inhaled) -The shape and arrangement of the cells may be disrupted -The bacteria may rinse off the slide (Not allowing the sample to air dry can result in the bacteria not adhering to the slide)

Encapsulated organisms are difficult to directly stain because ____.

-The capsule is not permeable to stains -The capsule does not react with most stains

Why did the nurse practitioner ask the patient questions regarding her lifestyle and history?

-The information may provide clues to help determine the source of the infection. -The timeline of events and onset of symptoms can provide helpful information in diagnosing infections.

The total magnification of an image is determined by ____ and _____.

-The magnification of the objective lens used -The magnification of the ocular lens

Select statements that correctly describe the process of bringing an object into focus with the 100x objective lens

-The object should first be focused under low power, then high power prior to using the 100x objective lens. -The intensity of light may need to be adjusted to optimize illumination. -A drop of immersion oil must be placed between the specimen on the slide and the 100x lens.

What is/are the advantage(s) of using a wet mount? Select all that apply.

-The specimen can be viewed as living cells. -The motility of a specimen can be viewed under the microscope.

While viewing this slide, it is difficult to distinguish cells from the background. Which of the following steps could remedy this situation?

-The specimen could be stained to improve contrast. -The light intensity could be decreased to improve contrast.

Which of the following are true with regards to enzymes?

-They can easily be recycled for use in further reactions -Possess an active site for interaction with substrate -They speed up the rate of metabolism

Which of the following are defining characteristics of fungi?

-They lack tissue differentiation -Fungal cell walls are composed of chitin -They are heterotrophic -They propagate by spores

What is the purpose of a negative stain?

-To determine morphological characteristics of the specimen -To visualize a capsule (if present) -To visualize the bacteria

When conducting a transfer between a broth culture and a sterile broth, you should use the Bunsen burner at which of the following times?

-To flame the mouth of the sterile broth tube after removing cap and before replacing the cap -To head the loop right before obtaining a sample from broth culture -To heat the loop right before obtaining a sample from broth culture -To flame the mouth of the culture broth tube after removing cap and before replacing the cap

You are conducting a transfer between a slant culture and a sterile slant. When should you use the flame of the Bunsen burner?

-To heat the loop after conducting the transfer to sterile slant -To flame the mouth of the slant culture tube after removing cap before replacing the cap -To heat the loop/needle right before obtaining sample from slant culture -To flame the mouth of the sterile slant tube after removing cap and before replacing the cap

During a broth to plate transfer, you should use the open flame at which points in the exercise?

-To heat the loop when you first take it from the receptacle -To heat the loop after the transfer is complete -To heat the mouth of the broth tube after removing cap and before replacing the cap

You are conducting a transfer between a slant culture and a sterile slant. When should you use the flame of the Bunsen burner?

-To heat the loop/needle right before obtaining sample from slant culture -To flame the mouth of the sterile slant tube after removing cap and before replacing the cap -To flame the mouth of the slant culture tube after removing cap and before replacing the cap -To heat the loop after conducting the transfer to sterile slant

This image depicts the results of an endospore stain performed on a smear of a known endospore-producing bacterial species. Which of the following could have let to the results shown here?

-Too many organisms were used -The primay stain was omitted -The smear was performed from a young culture that was not yet forming endospores

Which of the following would be appropriate for choosing a sample to perform a smear preparation? Select all that apply.

-Use bacteria from an isolated colony -Use only a small amount of bacteria on the loop (when performing a smear preparation, use bacteria from a single isolated colony)

Which of the following are characteristics of simple stains?

-Used to visualize morphology of bacteria (simple stains are frequently used to identify cellular morphology) -Used to identify cellular arrangements of bacteria (simple stains can be used to identify how bacteria are arranged. For example, clusters of cells versus chains of cells)

What methods can be used to count bacterial populations without culturing on plates?

-Using a flow cytometer -Completing a direct cell count -Analyzing turbidity of a broth

In which cases it is relevant to establish the number of bacterial cells in a sample?

-When determining if a patient has a bladder infection -When determining the purity of food or water -When determining the quality of milk

What might be observed microscopically in the wet prep that would indicate an infection?

-White blood cells -Microorganisms

You just performed an acid-fast stain on an acid-fast organism, yet some of the bacteria appear blue and some appear red. Which of the following could explain your results?

-You have a mixed population of bacteria in which some organisms are acid-fast and some are not -The primary stain was not allowed to stain long enough

List the basic steps of the streak plate method in the correct order from start to finish.

1. Heat an inoculate loop to red-hot and then allow to cool for at least 5 seconds 2. Remove the cap of the bacterial culture tube and flame the neck of the tube, and then remove a loopful of the culture using the sterilized inoculating loop. 3. Flame the mouth of the culture tube, return the cap to the tube, and return the tube to the test tube rack 4. Streak the plate with the inoculating loop being careful not to gouge the agar, flame the loop, allow it to cool and finish streaking the plate

Put the following steps in order to indicate a correct transfer from a bacterial culture to a sterile agar slant.

1. Heat inoculating loop, remove cap of bacterial culture, and heat mouth of tube. 2. Remove a small amount of bacteria, heat the mouth of tube, and replace cap. 3. Remove the cap from the sterile slant and heat mouth of tube. 4. Streak the sterile slant surface with the loop. 5. Heat mouth of newly inoculating slant tube and replace cap. 6. Heat loop before returning to its receptacle.

Put the following steps in order to indicate a correct broth to broth tube transfer.

1. Heat inoculating loop, remove cap of culture tube, and heat mouth of culture tube. 2. Remove a loopful of bacteria from the culture tube, heat the mouth of the tube, and replace cap. 3. Remove cap from sterile broth, heat mouth of tube, and insert loop into sterile broth. 4. Heat mouth of sterile broth, replace cap, and heat inoculating loop before replacing into receptacle.

Put the following steps in order for performing a smear preparation from a liquid culture.

1. Label the microscope 2. Apply a loopful of bacteria culture to slide 3. Air dry 4. Heat fix

Put the following steps in order for performing a smear preparation from a solid culture.

1. Label the slide with the name of the organism 2. Apply the loopful of sterile water to slide 3. Add very small amount of organisms to water on slide 4. Disperse organisms evenly over the center of the slide 5. Air dry 6. Heat fix

Place these steps in order for reading the absorbance of two bacterial samples.

1. Let the spectrophotometer warm up for 15 min. Set the wavelength to 550nm. 2. Calibrate the machine by inserting a cuvette with sterile medium and pressing reset button. 3. Remove cuvette and pour the sterile broth into the waste beaker. 4. Insert a clean cuvette with bacterial samples into the spectrophotometer and read the absorbance in the digital display. 5. Remove cuvette, pour bacterial sample into waste beaker, and rinse with water and repeat absorbance reading steps with a second sample.

At 50 degrees Celcius, agar is in the _1____ state and can be inoculated with a bacterial culture. When it reaches room temperature, it is in the ___2___ state, allowing for the formation of visible colonies during incubation.

1. Liquid 2. Solid

Each of the following steps are necessary in preparing and observing a wet mount. Place the steps in the correct order.

1. Obtain a clean slide and cover slip. 2. Using a transfer pipette, obtain a drop of specimen and place onto the center of the slide. 3. Carefully place the cover slip over the drop of specimen. 4. Observe preparation under the 10x objective lens. 5. Observe preparation under the 40x objective lens.

Place the following steps of the capsular stain in the proper sequence.

1. Place a drop of nigrosin on a clean slide 2. Add bacteria to nigrosin and mix 3. Spread the mixture over slide and air dry 4. Apply crystal violet 5. Rinse

Place the following steps in order to demonstrate your understanding of the viable plate count.

1. Place a small number of cells into a sterile broth 2. Incubate the broth for a set time period 3. Take a sample from the broth and plate onto solid media 4. Repeat (multiple times) the incubation of the broth and plating of sampling after the same set time period 5. Incubate all plates and count the colonies that developed

Indicate the correct order of steps (first step at the top) as you bring an object into focus under high power.

1. Place slide on stage and secure with stage clip. 2. Turn on the light and center the specimen over the light source. 3. Focus specimen on low power using coarse focus adjustment. 4. Use fine focus to sharpen the image under low power. 5. Rotate high power lens into position. 6. Readjust fine focus under high power to produce the sharpest image.

Place the following steps of the acid-fast stain in the proper sequence.

1. Stain with carbolfuchsin 2. Rinse off excess primary stain 3. Decolorize with acid alcohol 4. Rinse with water to stop the decolorization process 5. Counterstain with methylene blue 6. Rinse off excess counterstain 7. Blot dry

Rank the following organisms in terms of size, from smallest to the largest, with smallest at the top.

1. Staphylococcus (bacteria) 2. Candida albicans 3. Amoeba

List the steps of the standard plate count method in order from start to finish.

1. Transfer 1.0ml of bacterial culture to water blank A, shake, then transfer 1.0ml from blank A to blank B, and shake blank B 2. Transfer 0.1ml from blank B to the 1:100,000 plate, transfer 1.0ml to the 1:10,000 plate, and transfer 1.0ml to blank C and shake blank C 3. Transfer 0.1ml from blank C to the 1:10,000,000 plate and transfer 1.0ml to the 1:1,000,000 plate 4. Spread the transferred samples across the surface of the agar plates using an L-shaped spreader

List the steps of the pour plate method in order from start to finish.

1. Transfer one loopful of bacterial culture into tube I of nutrient agar, and then transfer one loopful of tube I into tube II of nutrient agar 2. Transfer one loopful of tube II into tube III of nutrient agar 3. Pour tube I into plate I, then pour tube II, and finally, pour tube III into plate III. 4. Allow the media to solidify and then incubate the plate in an inverted position

Correctly order the following steps for calibration of a spectrophotometer.

1. Turn on and allow to warm up for 15 minutes 2. Set the wavelength to 550nm 3. Insert a cuvette of sterile nutrient broth into the sample holder 4. Close the cover of the sample holder 5. Adjust the absorbance to 0 by hitting the reset button

If 141 colonies are counted on a plate that received 0.1ml of the 1:1,000,000 dilution, how many bacteria were present in 1.0ml of the undiluted culture? To calculate multiply the number of colonies by the dilution factor.

1.4 x 10^9

If a specimen was being viewed using a 100x objective and 10x oculars, what would be the total magnification?

1000x

Which lens will show the smallest area of the slide in the field of view?

100x

Which lens(es) require the use of immersion oil when viewing a specimen on a slide?

100x

If a specimen was being viewed using a 20x objective lens and 10x ocular lens, what would be the total magnification?

200x

The best time period to observe incubated cultures is between ___ hours.

24-48

Statistically reliable plates have no fewer than ____ and no more than 250-300 colonies.

30

What is the minimum number of colonies that must be present for a plate to be considered statistically valid?

30

Which would be the proper amount of time required for methylene blue dye to remain on the bacterial smear during a simple stain?

30 seconds to 2 minutes (This length of time should result in an approximately stained slide)

A standard temperature used for most incubations of bacterial cultures in the clinical microbiology lab is ______ degrees Celsius.

37

Of all the following objective lenses, which one was likely used to obtain image A?

40x

What lens could get dirty with oil if you move the revolving nose piece in the wrong direction after viewing under oil immersion?

40x

Counting 67 colonies on a plate with 1ml of the 1:1,000,000 dilution indicates that _____ bacteria were present in 1ml of the original sample.

6.7 x 10^7

Which slant shows a successful subculture?

A

Which slide shows both vegetative cells and endospores?

A

Which of the images depict a slice that was prepared from an excessive amount of microbial material?

A (This smear is too thick. The cells are not adequately dispersed for viewing of individual cells)

Which of the images represents staphylococci?

A (its blue)

Which of the following patterns could be used when streaking an agar slant?

A B

Which set(s) of serial dilution plates shows an unsuccessful dilution? Check all that apply.

A C

Which part of the microscope is indicated by the arrow?

Arm

Why might it be important to perform a Gram stain on bacterial cells?

As part of the information used to choose an appropriate antibiotic treatment

In order to maintain pure cultures, __________ technique must be used properly in the laboratory.

Aseptic

To prevent the introduction of unwanted organisms into an environment or culture, _______ technique is used.

Aseptic

What technique is used to prevent contamination of cultures in the laboratory?

Aseptic technique

Which of the images represents bacilli?

B

Which of the labeled colonies is a subsurface colony?

B

Which set of serial dilution plates shows a successful dilution?

B

Which plate shows the outcome of a plate that likely had bacterial culture added on each quadrant before streaking?

B (The heavy growth in every quadrant of plate B indicates that a new inoculum was introduced into each quadrant instead of loop sterilized in the frame between quadrants)

Which plate(s) show isolated colonies across most of the plate surface?

B (isolated colonies are present across and under the surface of this plate) A (isolated colonies are present across the surface of this plate)

Which image represents the correct position of an agar plate during incubation?

B: With the lid down

Bacterial cells that are rod-shaped are called _______.

Bacilli

Based on their cellular morphology, the red cells on this slide would be referred to as ________.

Bacilli

In a negative stain, which of the following is stained?

Background

Which of the following is stained during the first part of the capsule staining procedure?

Background of the slide

What is a bacterial smear?

Bacteria spread on a slide

Which of the following environments exhibited the highest amount of microbial contamination?

Benchtop (A)

Which of the following stains do not require heat fixation?

Capsule stain

In the Kinyoun acid-fast staining method, highly concentrated ______ is used to penetrate the cell wall and colorize acid-fast bacterial cells.

Carbolfuchsin

_____ is the initial stain used in the acid-fast stain.

Carbolfuchsin

All algae have _______ containing chlorophyll for photosynthesis.

Chloroplasts

What structure(s) provide motility for this microorganism?

Cilia

If methylene blue was omitted from the acid-fast stain, non-acid-fast cells would be _____ at the end of the staining process.

Clear

If safranin was omitted from the endospore stain, the vegetative cells would appear ______ in color.

Clear (colorless)

When first focusing a specimen, the ____ focus adjustment knob should be used.

Coarse

The arrow is pointing to the _____.

Coarse adjustment knob

Which of the following is used first to bring the specimen into focus with the low power objective lens?

Coarse focus adjustment knob

Which part of the microscope will be used first to adjust the focus when starting with the lowest power lens?

Coarse focus adjustment knob

A ______ on a streak plate is an isolated area of bacterial growth derived from one bacterium.

Colony

What term is used to describe a group of bacteria growing on an agar plate or slant that is derived from a single cell?

Colony

You spread individual bacterial cells evenly across the surface of a plate. After incubation, you will see that a ___ has formed from each isolated bacterium.

Colony

You take your plate out of the incubator, and you notice an unknown large fuzzy colony growing on the plate with mostly red smooth colonies. This would be an example of ____.

Contamination

If you are attempting to obtain a pure culture, what must you avoid when subculturing bacteria from a mixed plate to a sterile slant?

Contamination of the transfer tool or medium container

The image on the right illustrates improved ______ compared to the image on the left.

Contrast

What is enhanced when a stain is used to make a sample, or parts of a sample, darker than the background in a slide?

Contrast

Based upon this image, which component of microscopy could be altered to improve the visualization of this specimen?

Contrast (It is difficult to distinguish these bacteria from the background. The contrast must be improved by either staining the bacteria or reducing the light by partially closing the diaphragm.)

Which of the following organisms produce the toxins seen during "red tide" events in oceans around the world?

Dinoflagellates

Which of the following structures makes it difficult to stain endospores?

The endospore coat

Based on the image, what step of the capsular stain was omitted?

Crystal violet

What is the primary dye used in the Gram staining technique?

Crystal violet

Which stain is used to stain the cytoplasm of the cells in the capsule stain?

Crystal violet

What is used in the lab to support the growth of a microbial population?

Culture media

Bacterial cultures need to be placed into ____ for the use in the spectrophotometer.

Cuvettes

What microorganism is prokaryotic, photosynthetic, and often found in pond water?

Cyanobacteria

Living cells contribute to the turbidity of a culture, but _____ cells also contribute to the turbidity of a culture, which is a disadvantage of the indirect spectrophotometer method.

Dead

What phase of a typical growth curve is not usually seen when conducting density measurements with a spectrophotometer?

Death phase

In a differential staining technique, a ________ is used to remove the primary stain from the bacterial cell.

Decolorizer

Which group of algae have hard cell walls composed of silica?

Diatoms

Under the same environmental conditions, E. coli and S. aureus will likely show _____ growth rates.

Different

How do objects vary in their level of microbial contamination?

Different objects will vary in their level of contamination

To determine the number of bacterial cells in a sample, take the number of counted colonies and multiply by the _____ factor.

Dilution

The amount of light absorbed is _____ _____to the number of bacterial cells present in a sample.

Directly proportional

Which of the following are possible ways to correctly label the name of an organism on a glass slide?

E. coli

In order to withstand hostile conditions and facilitate survival, some bacteria produce resistant structures known as ________.

Endospores

Omitting the steaming in an endospore stain would result in which of the following?

Endospores would not take up stain

According to this data, which organism has the shortest generation (doubling) time under the environmental conditions of this exercise?

Escherichia coli (The curve for E. coli is the steepest, indicating rapid population growth due to a short doubling time)

Which of these microorganisms showed active movement?

Eugiena

The growth curve of bacteria shows a steep increase during the ______ phase.

Exponential

Microscopes make microorganisms appear larger than they are. This apparent increase in size is known as ____.

Magnification

The combination of lenses on a microscope increases the apparent size of an object, making an object that is too small to be viewed with the unaided eye appear larger. This is known as ______.

Magnification

Based upon this image, which component of microscopy could be altered to best improve the visualization of this specimen?

Magnification (These cells could be larger if you increased the magnification, but there is adequate contrast and resolution. You could switch to a higher power objective to improve the magnification.)

__________- is used to stain the endospore in the endospore staining procedure.

Malachite green green

Protozoa are often classified into different groups based on their ____.

Means of motility

Protozoa are traditionally classified into several groups based on their _______.

Means of motility

What actions are necessary to establish if a patient has a bladder infection?

Measure the number of bacteria in the urine

A substance that is used to support the growth of microbial life is referred to as a culture _______.

Medium

The pour plate method involves diluting one loopful of bacterial culture into a series of test tubes containing_______.

Melted nutrient agar

The counterstain used in the acid-fast stain is ______ _____.

Methylene blue

Which of the following approaches to the study of microorganisms enables direct viewing of microbial cells?

Microscopic

When observing Rhizopus, Penicillium and Aspergillus under the microscope, you notice long threadlike filaments typical of hyphae and large dark sportulating structures. Therefore, these organisms are examples of _______.

Molds

A chemical that fixes dye in or on cells by forming an insoluble compound is referred to as a(n) _________.

Mordant

Protozoans have been traditionally grouped according to their _______.

Motility

Which of the following is a significant lipid component of the cell walls of acid-fast bacteria?

Mycolic acid

If decolorization was omitted from the acid-fast stain, what color would non acid-fast cells appear?

Pink/Red

If methylene blue was omitted from the acid-fast stain, what color would acid-fast cells appear?

Pink/Red

Which image(s) represents a plate with growing bacteria?

Plate A Plate B

Which of the three plates represent poor or unsuccessful streak plates?

Plate A Plate B

Match each streak plate image with one of the descriptions.

Plate A- The loop overlapped into quadrant one when inoculating quadrant four. Plate B- Additional bacterial culture was added to the plate for each quadrant when making this plate. Plate C- The loop was too hot when obtaining an inoculum from the original culture.

Which of these plates shows a correct broth to plate transfer?

Plate B (squiggly line)

Agar _____ provide the most surface area for observing the characteristics of bacterial colonies.

Plates

What type of media provides the best option for obtaining a culture with isolated bacterial colonies?

Plates (Plates provide the largest surface area for growing isolated colonies. Individual colonies are not visible in a broth.)

One advantage of the ______ plate method is that it does not require a great deal of technical skill.

Pour

The _____ plate method may not be desirable because of all the materials (tubes, plates, media, hot plate) that must be used.

Pour

What technique would you choose to use in the following situations?

Pour Plate Technique- You want to isolate colonies so that they can be counted and used to calculate bacterial numbers in the original culture Streak Plate Technique- You want to use the quickest method to isolate colonies for subculturing, and you do not plan to count the number of colonies

Which of the following results in isolated colonies within the agar and on top of the agar?

Pour plate method

The first dye applied in a differential staining technique is referred to as the _______ stain.

Primary

The cells in the image seen here are _____ cells.

Prokaryotic

This protozoan possesses ______ for motility.

Pseudopodia

A culture that contains only one type of microorganism is called a __________ culture.

Pure

The goal of this exercise was to obtain a(n) ______ bacterial culture by subculturing part of one bacterial colony to a new sterile agar slant.

Pure

If decolorization was omitted from the acid-fast stain, what color would acid-fast cells appear?

Red

If malachite green was omitted from the endospore stain, vegetative cells would appear red in color.

Red (Malachite green stains the endospores. Safranin would stain the vegetative cells)

You want to compare the bacterial destiny in 3 different water sources. You dilute each sample 1:1,000 and plate on a petri dish. After 24h, the plates contain 500, 750, and 270 colonies respectively. What do you do?

Repeat the experiment by plating a series of dilutions for each sample

The ability to distinguish fine detail in a cell is _______.

Resolution

The ability to distinguish fine detail or discriminate between two very closely spaced objects is called ____.

Resolution

Which of these tubes shows the result of a correct broth to broth transfer? (clear to cloudy tubes)

Tube B

How would you describe the morphology and arrangement of the bacteria in the image?

Streptobacilli

Spherical cells arranged in a chain are called _______.

Streptococci

The morphology and arrangement of the organism represented in the image would be characteristic of the genus _____.

Streptococcus

The morphology and arrangement of this organism is characteristic of members of what genus?

Streptococcus

The small oblong-shaped colonies that grow after pour plating are ____ colonies.

Subsurface

Match the type of pour plate colony with its description.

Surface colony- Bacterial colony growing on the top of the agar Subsurface colony- Bacterial colony growing inside the agar

When determining the number of bacteria in a sample, the dilution factor needs to be multiplied by what amount?

The amount of bacterial colonies on a plate

What is stained by the initial dye in the capsular stain procedure?

The background

You have just performed an acid-fast stain, and all of the cells appear to be blue. Which of the following could explain your results?

The bacteria are non-acid-fast

Why is it necessary to dilute a sample in order to determine bacterial numbers?

The bacterial density in the original sample may be too high for the formation and counting of isolated colonies (The main reason for dilution is to obtain isolated colonies for accurate counting)

Which of the following descriptions reflects observations of a capsular stain that may have been heat fixed?

The capsules cannot be seen clearly on the slide (Applying heat during the staining process can shrink or destroy the capsule)

You decide to make a plate counting experiment. What would happen if you plated undiluted bacteria culture directly on the plate?

The colonies would be too close for counting

What adjustment to the microscope was made between the image on the left and the image on the right?

The course or fine focus knob was adjusted

Which of the following describes the correct method for heat fixation?

The heating should be very brief. Passing the slide though the flame for 3-5 seconds is enough

A student thought she had inoculated this plate the prior day, but this is what was observed after incubation. What might have occurred in the transfer to this plate?

The inoculating transfer tool was heated at an incorrect time, killing the inoculum before she streaked the plate

How is a glass culture tube handled during aseptic technique?

The mouth is passed through the flame right when opened and just before closing.

What is stained by the counterstain in the acid-fast stain procedure?

The non-acid-fast organisms on the slide

If you do not move the specimen in this image to the middle of the viewing field, what may happen when you change to higher levels of magnification?

The penicillium structures may no longer be in the field of view

This image shows the results of an endospore stain performed on an endospore-producing strain of bacteria. Identify which step in the endospore stain was omitted in order to get the results depicted in this slide.

The primary stain, malachite green, was not used

A successful broth to broth transfer is partly indicated by _____ in the sterile broth after incubation.

Turbidity

Why is it important to air dry the bacteria before they are immobilized by heat fixation?

This ensures the optimal preservation of the bacterial morphology (Too much water on the slide during heating can lead to disruption of the bacterial morphology. Air drying before heat fixation reduces this effect)

Why is 35-37 degrees Celsius a standard incubation temperature range for many lab exercises involving medically important bacteria?

This range is close to human body temperature, a temperature preferred by many of these organisms.

Which of the following is not considered a microorganism?

Tick

Why is it necessary to dilute a culture when plating bacteria for a counting experiment?

To achieve a density that allow the individual colonies to be distinguished during counting

Why is it necessary to perform a serial dilution during the standard plate count method?

To achieve isolated bacterial colonies that can be reliably counted

What is the purpose of the smear production?

To allow for visualization of individual bacteria

What is the purpose of the Gram staining technique?

To characterize unknown bacteria

The very first and last step to every microbiology lab exercise is________.

To disinfect the lab bench

What is the purpose of the slanted surface in an agar slant?

To increase the surface area for observable growth

What will be the correct procedure for transferring bacteria?

To use a new clean pipette each time you sample from a different bacterial culture

Staining allows for the visualization of bacterial cells because it increases contrast during microscopic imaging.

True

True or false: This image likely depicts a Gram stained slide.

True

Two clinically significant genera of bacteria that are capable of producing endospores are Clostridium and Bacillus.

True

All three factors affecting the quality of a microscopic image can be controlled by manipulating the actual microscope.

True (Magnification and resolution are affected by the mechanics of the microscope itself. Selecting a higher power objective lens and the use of immersion oil can improve magnification and resolution, within limits. While contrast can be enhanced by altering the specimen (staining), it can also be improved by reducing the amount of light when viewing the specimen.)

When plated on culture media, samples from most environments will reveal microbial growth.

True (The fact that bacteria are ubiquitous does mean that most environments will reveal microbial growth)

Environments with _____ temperatures are likely to show more bacterial growth on an exposed agar plate.

Warmer (Many environmental bacteria prefer temperatures at or above room temperatures such as 37 degrees in an incubator. Therefore, warmer temperature environments are more likely to promote bacterial growth than colder environments)

When creating a serial dilution for the standard plate count method, ____ blanks are used and then a sample from these blanks are added to petri plates.

Water

There are many types of staining techniques used in microbiology. Which of the following is not a commonly used staining technique?

Wright's stain

A unicellular fungus that reproduces by budding is a ______.

Yeast

Did the student correctly handle the inoculating loop?

Yes (The student correctly heated the inoculating loop before she sampled the culture and after using it to transfer bacteria to the sterile medium.)

You have successfully focused an object with the high power objective. After adding a drop of oil you have rotated the 100x objective into position. You are now looking through the microscope, trying to sharpen the image and suddenly the slide breaks. What is the most likely explanation?

You are using the coarse focus adjustment knob.

After viewing a slide under oil immersion, what could happen if you rotated the nose piece in the wrong direction before removing the slide?

You could drag the 40x objectives through the oil, making it dirty.

You inoculate a sterile broth with E. coli but after 48 hours of incubation at 37 degrees Celsius, the medium remains clear. Which of the following errors may have occurred?

You picked up the inoculum from the bacterial culture while the loop was still too hot

If your inoculated slant shows no growth after incubation, what may have occurred during bacterial transfer?

You sampled the bacteria while the loop was still too hot

A capsule stain was performed, using crystal violet as a primary stain, followed by a water rinse, and then nigrosin as a counterstain. As you observe the slide through the microscope, you suspect you made an error. Which of the following is most likely problem with your technique?

You should have started with nigrosin as the primary stain and used crystal violet as a counterstain