Chapter 3 Lab Questions
mixed culture
A culture which contains two or more species which can be easily differentiated
Which microscope shows cells against a bright background and the intracellular structures of unstained cells based on their varying densities?
Phase-contrast
Which of the following ingredients makes Mannitol Salt Agar (MSA) selective for Staphylococcus species? Agar Crystal violet Mannitol Salt
Salt
Examples of streak plates
A: poor because quadrant 1 overlapped with quadrant 4 B: unsuccessful because either forgetting to flame the loop or adding new culture into each quadrant C: successful
Which of the following determines the type of microbe at the species level? Incubation Identification Inspection Isolation Infection
Identification
The goal of subculturing part of one bacterial colony to a new sterile agar slant is to obtain a(n) _________.
Pure bacterial culture
You accidentally switch the Crystal violet and Safranin steps during your Gram stain. When you look under the microscope, what color will a Gram positive bacteria, like Staphylococcus aureus, be?
Purple
Motility test medium is an example of what type of media?
Semi-solid
Absorbance or optical density is measured using a
Spectrophotometer
What happens when the loop is too hot when obtaining an inoculum from the original culture
The dish remains blank
What is incorrect/missing in the steps below for the proper technique for making a smear? • Label a slide. • Place a small drop of water on the slide. • Gently pick up an isolated colony from a Petri dish. • Immerse and suspend the colony. • Sterilize the inoculating loop. • Let slide dry for five minutes.
The inoculating loop should be sterilized before picking up a colony from the dish.
Why can dyes be used as differential agents in media? They serve as growth factors. They have inhibitory properties. They are weak salts. They are pH indicators.
They are pH indicators.
When can pour plating be used?
When determining bacterial numbers in a sample and when obtaining isolated colonies for making pure cultures
Where do colonies grow on pour plates?
Within the agar & on the agar surface
The selective agent in MacConkey Agar is _______ salts
bile
What general type of stain is used to separate types of bacteria based on their cellular structures?
differential
A ___________ culture is a container that holds two or more easily differentiated species of microorganisms.
mixed
The term used to describe a cluster of circular bacteria is
staphylococcus
Isolation methods
streak plate, spread plate, pour plate
used to provide high-resolution images of internal structures of cells and viruses
transmission electron microscopy
Stuart's and Amie's _______ media contain buffers and absorbants to prevent cell destruction but will not support growth.
transport
________ media are used to maintain and preserve specimens that have to be held for a period of time before clinical analysis.
transport
Which of the following is described as a medium which has known quantities of every ingredient within it? Complex Defined Undefined Synthetic
Defined and synthetic
How to streak a plate from quadrant 1-4
Do not obtain a new culture of bacteria when streaking quadrants 2-4. Quadrants 1 and 4 should not overlap
Which microscope achieves the greatest resolution and highest magnification?
Electron
T/F: It is necessary to use a colony counter when completing a standard plate count
False
True or False: The thinner peptidoglycan layer of gram-positive bacteria allows the crystal-violet-iodine complex to leave the cell.
False
a successful streak plate provides ______ colonies to the top of the agar which may be used to further study
isolated
If the agar is allowed to cool properly the agar surface will be _____
smooth
contaminated culture
A culture which contains one or more unwanted and often unidentified microbes
methods of bacterial isolation
A: quadrant streak plate method B: pour plate method C: serial dilution and plating method
Examples of dilution plates
A: unsuccessful dilution B: successful C: original bacterial culture was not adequately diluted
Why do you have to flame the loop between each streak?
Flaming the loop between streaks ensures that the loop starts clean and that only this small amount of bacteria is used to inoculate the next quadrant
Which are advantages of the streak-plate method when compared to the pour-plate method?
It is a very quick process and it requires less materials.
Identify all of the following conditions which modern incubators can regulate. Temperature Moisture Salinity Atmosphere conditions (Gases)
Temperature, moisture, and atmosphere conditions (gases)
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
How do you calculate bacterial concentration (cfu) for colonies?
cfu/ml = (no. of colonies x dilution factor) / volume of culture plate For example, suppose the plate of the 10^6 dilution yielded a count of 130 colonies. Then, the number of bacteria in 1 ml of the original sample can be calculated as follows: Bacteria/ml = (130) x (10^6) = 1.3 × 10^8 or 130,000,000.
You spread individual bacterial cells evenly across the surface of the plate. after incubation , you will see that a ____ has formed from each isolated bacterium
colony
Under the same environment conditions, E.coli and S. aureus will likely show _______ growth rates.
different
To determine the number of bacterial cells in a sample, take the number of counted colonies and multiply by the ______ factor
dilution
specimen is contrasted against a gray background, well-suited to visualize intracellular structures
phase-contrast microscopy
information gathering
testing of cultures using procedures that analyze biochemical and enzyme characteristics, immunological reactions, drug sensitivity, and genetic makeup
VBNC is the abbreviation for ________ but _________ and may describe most of the microbes in the environment.
viable, nonculturable
analyzing the genotype of an organism
DNA profiles
What items are needed to perform a serial dilution for the standard plate count method?
-Bacterial culture -Nutrient agar -Petri plates -Pipets -Water blanks
What percentage of agar is typically added to nutrient broth to make nutrient agar? 1% to 5% Excess of 25% 15% to 25% 6% to 10%
1% to 5%
Bacterial growth chart phases
A: lag phase B: log phase C: stationary phase
If a Gram stain of the CSF sample yielded gram-positive cocci, what would be the likely causative agent? A. Neisseria meningitidis B. Streptococcus pneumoniae C. Measles virus D. Haemophilus influenzae
B. Streptococcus pneumoniae
If a Gram-stained slide of the CSF sample was void of cells, what would be the likely causative agent? A. Neisseria meningitidis B. Streptococcus pneumoniae C. viral agent D. fungal agent
C. viral agent
Media ingredients that cannot be chemically defined include which of the following? Cell secretions Disodium hydrogen phosphate Extracts of animals, plants, or yeasts Sodium chloride Blood and serum
Cell secretions Extracts of animals, plants, or yeasts Blood and serum
Motility test media has approximately how much agar in it? 0.3-0.5% 1.3-1.5% 1.0-3.0% 10.0-30.0%
0.3-0.5%
Which tests determine the fundamental chemical characteristics of microbes such as presence of enzymes? Biochemical Macroscopic Genetic Microscopic
Biochemical
What are disadvantages of the streak plate method?
Cannot enumerate bacteria after incubation Requires practice to master the skill of inoculating the plate
_________ is the name of the equipment which is used to precisely regulate the environment for microbes to grow.
incubator
Which of the following results in isolated colonies within the agar and on top of the agar? Streak plate method Pour plate method Spread plate method
Pour plate method
When studying population growth curves with a spectrophotometer, it is unlikely that you will see the typical steep decrease of the curve during the death phase because __________
the spectrophotometer measures turbidity of the tube, which is influenced by both living and dead cells
List the steps of the pour plate method in order from start to finish.
1. Liquefy nutrient agar tubes and maintain at 50 degrees C. 2. Transfer one loopful of bacterial culture tube I of nutrient agar, and then transfer one loopful of tube I into tube II of nutrient agar 3. Transfer one loopful of tube II into tube III nutrient agar 4. Pour tube I into plate I, then pour tube II into plate II, and finally, pour tube III into plate III 5. Allow the media to solidify and then incubate the plate for 24-48 hrs in an inverted position.
Which of the following identifies the method that requires you to serially dilute microorganisms by passing them from one tube of cool but still liquid agar to another, and then eventually pouring them into petri plates with the intended purpose of obtaining individual colonies? Loop dilution method Streak plate method Spread plate method
Loop dilution method
When not carefully selecting an isolated colony to subculture a slant, what will the growth pattern be on the on an incubated tube?
More than one type of colony
Which of the following is media that has a firmness midway between that of a broth (a liquid medium) and an ordinary solid medium? Chemically defined Semiliquid media Seminutrient media Semisolid media
Semisolid media
What concentration of gelatin should be added to broth to make a solid medium for bacterial growth? 20-25% 10-15% Greater than 25% 1.0-1.5%
10-15%
subculture
A second-level culture where an isolated colony from one culture is taken and transferred into a new medium
Where are colonies formed during the pour plate method? Colonies grow only on the surface of the plates. Colonies grow on the surface and within the medium.
Colonies grow on the surface and within the medium.
All of the following apply to the loop dilution and pour plate method except which one? The number of cells is reduced in each liquid agar tube. Colonies grow on the surface and within the medium. Cells have ample space to grow into discrete colonies. Colonies grow only on the surface of the plates.
Colonies grow only on the surface of the plates.
Brain-heart infusion, trypticase soy agar (TSA), and nutrient agar are all examples of which type of media?
Complex
When a culture shows two or more microbes of uncertain identity that have been introduced into it, the culture is considered to be which of the following? Contaminated Axenic/pure Mixed
Contaminated
Which is incorrect about chocolate agar? It can be used to cultivate Neisseria. It usually uses sheep blood that has been heated. It has chocolate extract in it. It is an enriched medium. It is used to grow fastidious bacteria.
It has chocolate extract in it.
multipurpose technique for live and preserved specimens; specimen is dark, field is white
bright-field microscopy
Rod-shaped bacteria ________.
can be either gram-positive or gram-negative
What is the correct order of staining materials used in the Gram stain technique?
crystal violet, Gram's iodine, 95% ethanol, safranin
provides detailed, high-contrast images of live specimens
differential-interference microscopy
The amount of light absorbed is ___ to the number of bacterial cells present in a sample.
directly proportional
Fluid thioglycollate is a slightly viscous broth used to determine patterns of microbial growth in which gas? Hydrogen Nitrogen Hydrogen sulfide Oxygen Carbon dioxide
oxygen
A ________ medium contains a substance such as thioglycollic acid which reduces the availability of oxygen in the medium.
reducing or anaerobic
Proper pour plate examples
A & B are improper C is correct because there are colonies
Indicate which of the following are important considerations when using the spectrophotometer to determine absorbance of bacterial cultures: A. Use a cuvette of sterile nutrient broth to zero the absorbance B. Be sure a properly align the cuvette each time in cuvette holder C. Handle only the top of the cuvette and carefully wipe the cuvette with Kim wipes to remove any smudges. D. Shut the cuvette holder cover whenever reading absorbance or transmittance. E. Set Transmittance at 0% with a curvette of sterile water in the holder
A-D are correct
After Gram's iodine is added, what color do the cells appear under a light microscope?
All cells appear purple
Identify the selective agent in EMB agar. Safranin Crystal violet Bile salts Vinegar
Bile salts
Which is a common component found in feces and, therefore, used in media to selectively culture Gram-negative bacteria? Vinegar Bile salts Malachite green Crystal violet
Bile salts
Which of the following is an organic compound, such as a vitamin or amino acid, that must be provided in the diet to facilitate survival of certain bacteria. Growth factor Mineral Dye Glucose
Growth factor
In lab, Isaac was given a mixed culture. His objective is to isolate single colonies. What should he use to accomplish this goal?
Inoculating loop, incinerator, streak plate method, 37 degree Celsius incubator
Identify all the correct answers associated with liquid media. Liquid media are also called "broths" Liquid media allows for the production of individual colonies. A slightly viscous liquid medium can be used to better understand the oxygen demands of microorganisms Liquid media typically affords greater microorganism growth.
Liquid media are also called "broths" A slightly viscous liquid medium can be used to better understand the oxygen demands of microorganisms Liquid media typically affords greater microorganism growth.
What action is necessary to establish if a patient has a bladder infection?
Measure the number of bacteria in the urine
If the Gram's iodine step was skipped in this technique, what would likely be seen under the microscope?
Most cells would appear red/pink.
Why must fresh cells be used when performing a Gram stain?
Old cells may not Gram stain properly.
During the steps of the streak plate method, the bacterial culture is only added to the plate ______ time(s)
One
Identify all the benefits of using solid agar compared to using liquid media.. Provides a firm surface on which cells can form discrete colonies Useful for isolating fungi Useful for isolating bacteria Solid agar allows greater growth of microorganisms.
Provides a firm surface on which cells can form discrete colonies Useful for isolating fungi Useful for isolating bacteria
How do you accurately describe a successful pour plate?
Smooth agar surface with colonies on the surface and within the agar
In brain heart infusion broth (a complex, nonsynthetic media), none of the ingredients can be chemically defined, except which of the following? Beef extract Peptone extract Sodium chloride Brain extract
Sodium chloride
At room temperature, agar will always be which of the following? Solid Selective Liquid
Solid
How does the loop dilution/pour plate technique result in colony isolation? The sample is serially diluted before dispensing into petri dishes. Spread on the surface Introduced by a needle allowing isolated subsurface growth The sample is partially killed by the melted agar.
The sample is serially diluted before dispensing into petri dishes.
pure culture
The type of culture most frequently used in the laboratory which contains only a single species of microbe
What microbe requires live media for growth?
Viruses
Identify the polysaccharide found in seaweed that is commonly used to prepare solid culture media. Starch Peptone Agar Gelatin
agar
using macroscopic and microscopic traits for identification
appearance
The technique of subculturing bacteria is used to obtain pure or ________ cultures.
axenic
tests that determine chemical characteristics including enzyme production and nutritional requirements of the microbe
biochemical tests
During the lag phase, __________.
cells are engaged in intense enzymatic activity
best for live, unstained specimens; specimen is bright, field is black
dark-field microscopy
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
The ____ phase of a typical growth curve is not usually seen when conducting density measurements with a spectrophotometer
death
The differential stage of the Gram stain is the application of _____.
ethanol
At 50 deg. Celsius, agar is in the ______ state and can be inoculated with a bacterial culture. At room temperature, agar is in the ______ state, allowing for the formation of visible colonies during incubation
liquid, solid
When creating a culture, the inoculating _____ is the best tool to use to avoid tearing the agar
loop
In the pour plate method, tubes filled with _____ are inoculated and used to make plates
melted agar
The pour plate method involves diluting one loopful of bacterial culture into a series of test tubes containing ________
melted nutrient agar
Isolation
methods for separating individual microbes and achieving isolated colonies that can be readily distinguished from one another macroscopically
_________ solid media do not melt and contain materials such as rice grains, cooked meat media, and potato slices.
nonliquefiable
Serial dilution and the standard plate count (SPC) method are used to determine the ___________ of organisms present in a bacterial culture
number
inspection
observing cultures macroscopically for appearance of growth and microscopically for appearance of cells
When ethanol is applied correctly, gram-positive cells appear ____ and gram-negative cells appear _____.
purple, colorless
When preparing pure cultures, dilution is necessary for:
reducing the number of inoculated organisms so that isolated colonies can develop
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
Please select all of the statements which are TRUE regarding isolated colonies. -Isolated colonies form on solid nutrient media. -Isolated colonies form in liquid nutrient media. -A colony results from a single cell or a cluster of cells multiplying into a visible mass. -The cells within the colony are all the same species. -Isolated colonies can only be obtained via the streak plate method.
-A colony results from a single cell or a cluster of cells multiplying into a visible mass. -The cells within the colony are all the same species. -Isolated colonies form on solid nutrient media.
You have a nutrient broth, an agar slant, and an agar plate with bacterial growth in or on each. If you wanted to evaluate the macroscopic appearance of the bacteria growing in or on the medium, which of the cultures would be the best choice?
Agar plate
What happens during the death phase of bacterial growth?
At death phase, the population dies because of inappropriate living conditions (exhausted nutrients, oxygen, wrong temperature, etc.).
T/F: Once a standard curve has been prepared by plotting numbers of bacteria (CFU/mL) versus absorbance for one species of bacteria, this curve can be used for estimating bacterial numbers by measuring absorbance for any species of bacteria.
False???
How do you know if the streak method was successful?
If you were able to successfully isolate single bacterial colonies
You want to compare the bacterial density in 3 different water sources. You dilute each sample 1:1,000 and plate on a petri dish. After 24hr, the plates containing 500, 750, and 270 colonies respectively. What do you do?
Repeat the experiment by plating a series of dilutions for each sample
Which of the following is not true for viruses? Some viruses can be grown in chicken eggs Some viruses can be grown in nutrient agar Must grow within a cell Cannot replication on their own
Some viruses can be grown in nutrient agar
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
A ______ is a mound of cells on a solid medium that represents the progeny from one original bacterial cell.
colony
A _______ on a streak plate is an isolated area of bacterial growth derived from one bacterium
colony
Why is it important to avoid contamination when subculturing to a slant?
the goal is to form a pure culture so the species can be identified and tested
What type of media is being described in the example? 1. Blood agar uses sheep blood to help grow fastidious microbes including streptococci. 2. MacConkey agar isolates gram-negative enteric bacteria by inhibiting growth of gram-positive bacteria. 3. Staphylococcus aureus can be identified on mannitol salt agar (MSA) because it ferments the mannitol, changing the color of the agar from pink to yellow. 4. Also known as synthetic media, this type of media has a defined molecular content and varies very little from one source to another. 5. Also known as non-synthetic media, these media cannot be chemically defined because they are partly produced from organic extracts of tissues, cells, or other biological materials.
1. Enriched 2. Selective 3. Differential 4. Chemically defined 5. Complex media
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
Statistically reliable plates have no fewer than ___ and no more than 250-300 colonies
30
Once liquefied, agar does not resolidify until it cools to what temperature? 42 C 60 C 100 C 75 C
42 C
Which of the following will result when 1% to 5% agar is added to nutrient broth, boiled and cooled? A pure culture A mixed culture A solid medium A liquid medium A contaminated medium
A solid medium
When completing a quadrant streak, when do you flame the loop? A. Before you streak quadrant one B. Before you return the loop to the receptacle C. Before you streak quadrant two and three D. Before you pickup a loopful of organisms from the original culture
B, C, and D
Plates showing isolated colonies
Both B&C show isolated colonies across most of the plate surface
You are doing research on a bacterial species, trying to determine the nature and structure of a number of intracellular inclusions. Which type of microscopy would provide the best view of these intracellular structures?
Transmission electron microscopy
_______ is a solidifying agent used in media that melts at 100°C and does not resolidify until it reaches 42°C.
agar
identification
analysis of collected data to help support a final determination of the types of microbes present in the original sample; this is accomplished by a variety of schemes
Identify which of the following media are considered nonsynthetic media: Brain heart infusion media Minimal media for fungi Blood agar
brain heart infusion media and blood agar
What type of medium is described? Several types of organisms grow but show visibly different reactions
differential medium
Dyes can be used as differential agents because many of them are __________ indicators which change color in response to the production of acids or bases.
pH
Inoculation
placing a sample into a container of medium that supplies nutrients for growth and is the first stage in culturing
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 of the materials (tubes, plates, media, hot plate) that must be used.
pour
______ media are useful for growing anaerobic bacteria.
reducing
used to capture surface images of cells and viral particles
scanning electron microscopy
What type of medium is described? Grows some types of organisms but restricts other types
selective medium
All of the following are criteria that are used to classify different types of microbiological growth media except: physical state or consistency purpose or function chemical composition sensory characteristics (color, smell)
sensory characteristics (color, smell).
An indirect method of estimating bacterial numbers is based on the turbidity of the sample. A ________ can be used to determine the turbidity by measuring absorbance.
spectrophotometer
The ______ plate method involves spreading an inoculum onto the surface of a plate in a pattern that results in isolated colonies in some areas of the plate after incubation, whereas the ______ plate method involves diluting an inoculum into several melted agar tubes and then adding their contents into plates for solidification and incubation
streak, pour
A bacterial growth curve shows the growth of cells over time. There are four basic phases of growth are:
the lag, log, stationary, and death phases
Which is NOT a purpose of using the Gram-stain in the diagnostic process? to confirm the identity of the pathogenic agent to give guidance for drug treatment to determine that the infection is bacterial instead of viral to determine what type of bacteria may be causing the infection
to confirm the identity of the pathogenic agent
T/F: Mannitol Salt Agar (MSA) is typically used to grow Gram-negative bacteria.
False
Agar as a media solidifying agent has many benefits including which of the following? Not digestible as a nutrient by most microbes Retaining moisture and nutrients Providing a nutrient source to the media Not harmful to microbes or humans Being flexible and moldable
Not digestible as a nutrient by most microbes Retaining moisture and nutrients Not harmful to microbes or humans Being flexible and moldable
What two things result in better resolution?
Shorter wavelength and larger numerical aperture
Nutrient agar is an example of what type of media?
Solid
A sterile tool called a "hockey stick" is used in which bacterial isolation technique? Streak plate Spread plate Pour plate Loop dilution
Spread plate
Which of the following are characteristics of an enriched medium? Can be used to aid in the growth of fastidious organisms May contain special growth factors Contains antibiotics to assist in keeping cultures pure May contain organic substances such as blood, serum or hemoglobin Its components are always chemically defined
Can be used to aid in the growth of fastidious organisms May contain special growth factors May contain organic substances such as blood, serum or hemoglobin
What is true for pour plating but not for quadrant streaking?
-Isolated colonies form within the agar plate -It requires the use of multiple tubes and plates
Media that allows the growth of multiple types of microbes but are designed to distinguish characteristics among members of the culture are called which of the following? Selective media Special media Differential media Specific media
Differential media
Which of the following is a medium that works by showing two reaction types, such as a color change in some colonies but not in others? Differential medium Selective medium Enriched medium Minimal medium
Differential medium
Identify a medium which contains complex organic substances and/or special growth factors which allows even fastidious organisms to thrive. Enriched medium Selective medium General medium
Enriched medium
Which of the following is absolutely true for all viruses? Must grow in or on living cells Must be resistant to light Must be airborne
Must grow in or on living cells
What are the 6 I's of culturing microbes?
inoculation, isolation, incubation, inspection, information gathering, identification
A microbiologist inoculates Staphylococcus aureus into a culture medium. Following incubation, both Staphylococcus aureus and Staphylococcus epidermidis are determined to be growing in this culture. What is the most likely explanation?
The culture is contaminated
The streak plate technique works by using an inoculating loop to spread a bacterial sample in a pattern that thins it out but this only works if which of the following is done? The culture is pure to begin with. There is a new diluted sample added at each step. The inoculating loop is re-sterilized at each thinning step of the pattern. The inoculating loop is sterilized only at the beginning of the pattern.
The inoculating loop is re-sterilized at each thinning step of the pattern.
When subculturing to make a pure culture, what bacteria should be used
isolated bacterial colony
Incubation
exposing the inoculated medium to optimal growth conditions, generally for a few hours to days
tests the organism against known antibodies to determine if there is a reaction between the organism and the antibody
immunological testing
How many types of bacteria are on a successful subculture to a slant?
one
When E. coli metabolizes lactose in a differential medium that colonies produced are which color? Creamy white Green Red to pink Blue to violet
Red to pink
Which of the following are obligate parasites? Yeasts Fungi Rickettsias Viruses Most bacteria
Rickettsias Viruses
Which type of medium is essential for development of discrete, isolated colonies?
Solid medium
Identify the inoculation technique that uses a sterile tool, such as an L-shaped glass rod, to distribute the sample evenly around the surface of a plate? Loop dilution technique Streak plate technique Pour plate technique Spread plate technique
Spread plate technique
Which of the following media are chemically definable? Synthetic Nonsynthetic
Synthetic
Which of the following represent inoculation of a microbial sample? Sequencing of the microbial DNA Streaking a sample on an agar plate Placing a sample in sterile medium Maintaining a sample at body temperature Examining a microbe under the microscope
Streaking a sample on an agar plate Placing a sample in sterile medium
Which of the following describes a second-generation culture made from a well-established colony of microorganisms? Axenic Pure Primary Subculture
Subculture
Which of the following describe selective media? Select for growth of a broad spectrum of organisms Suppress unwanted organisms Display visible differences among microorganisms Encourage the growth of desired organisms
Suppress unwanted organisms Encourage the growth of desired organisms
What cautions should be taken when the pour plates are placed in the incubator?
The agar plates should be allowed to solidify at room temp before moving them to the incubator The plates should be placed in the incubator UPSIDE DOWN
Which of the following describes general-purpose media? They are usually chemically defined synthetic media. They include nutrient agar and broth. They usually contain a mixture of nutrients. They are usually nonsynthetic. They grow a broad spectrum of microbes. They include Mannitol salt and MacConkey agar.
They include nutrient agar and broth. They usually contain a mixture of nutrients. They are usually nonsynthetic. They grow a broad spectrum of microbes.
T/F: Liquid media can be used to better understand the oxygen demands of a microorganism.
True
Correct amount of material that should be sampled when subculturing a colony of bacteria
A is correct
Nonliquefiable solid media can contain one of the following materials as the solidifying agent except which of the following? Cooked meat media Potato slices Agar Rice grains
Agar
Identify all of the following which are considered growth factors typically added to enrich culture media. Amino acids Agar Blood Vitamins
Amino acids Blood Vitamins
True or False: All bacteria can be classified as either gram-positive or gram-negative.
False
True or False: Bacteria are larger than human cells.
False
Which of the following reagents reacts with crystal violet as the mordant? Crystal violet Gram's iodine 95% ethyl alcohol Safranin
Gram's iodine
A student was given a stained smear to observe. Upon observation, the student noted rod-shaped bacteria that were clear and unstained against a darker background. What sort of stain was performed on this slide?
Negative stain
_________ plates allow you to observe colonies under the surface of the agar, where ________ and serial dilution plates only show surface growth.
Pour, streak
General-purpose media are characterized by which of the following? They allow the growth of a broad range of microbes. They contain only one nonsynthetic nutrient. They are synthetic and chemically definable.
They allow the growth of a broad range of microbes.
A microbiologist makes a fixed smear of bacterial cells and stains them with Loeffler's methylene blue. All the cells appear blue under the oil lens. This is an example of ________
simple staining
Types of stains
simple, differential, structural
In what situations could standard plate count could result in an underestimate of the 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
List the basic steps of the streak plate method in correct order from start to finish
1. Heat an inoculate loop to red-hot and then allow to cool for at least 5 sec 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
What are the steps, in order, for reading the absorption of two bacterial samples?
1. Let the spectrophotometer warm up for 15 minutes. 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 sample into spectrophotometer and read the absorbance in the digital display 5. Remove the cuvette, pour bacterial sample into the waste beaker, and rinse with water and repeat absorbance reading steps with a second sample
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 teh 1:10,000 plate, and transfer 1.0ml to blank C and shake blank C 3. Transfer 0.1ml from blank C to the 1:10,000,000nplate 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
What may indicate that you have correctly subcultured an organism from a plate to a slant?
After Gram staining a smear prepared from the slant, all of the cells have similar color and morphology under the microscope.The slant shows only one color of growth.
What is the log phase of bacterial growth?
During the log phase, the bacteria are dividing at the fastest possible rate under the conditions provided.
What occurs during the stationary phase?
During the stationary phase, the growth rate slows and the number of microbial deaths balances the number of new cells, and the population stabilizes.
