Microbiology lab final test
Place these steps in the order in which they will be performed when setting up a disk diffusion assay to test the effectiveness of disinfectants and antiseptics.
1. Using a swab, inoculate a suspension of the bacteria being tested onto an agar plate, spreading the inoculum over the entire surface. 2. Saturate sterile filter paper disks with the test chemical (disinfectant or antiseptic) and place onto the inoculated agar plate.Repeat with each chemical being tested. 3. Incubate inoculated agar plates overnight to promote bacterial growth. 4. Observe plates to determine the presence of a zone of inhibition around each antiseptic or disinfectant disk.
Match the result with the description of observation that it represents 1. positive results for catalase 2. negative results for catalase
1. bubbles will form upon addition of hydrogen peroxide 2. bubbles will not form upon addition of hydrogen peroxide
pair types of hemolysis with color around colony 1. beta 2. gamma 3. alpha
1. clear, transparent 2. no color change 3. greenish
The total magnification achieved when using 100x oil immersion lens with 10x binocular eyepiece is______
1000x
Which of the flowing objectives should be used with immersion oil?
100x objective
Which of the following objective magnifications is best for observing bacteria?
100x objective
How long should Hands be lathered while washing?
20 seconds
Enzymes in human cells tend to perform best
37°C
Yeast tubes with sugar and respirometers need to be incubated at 37°C because:______________
37°C is the optimal temperature necessary for yeast to grow lower temperatures may cause the metabolism to slow down to undetectable levels higher temperatures may kill the yeast
You are studying a bacterium found in the normal intestinal flora of humans and most other mammals, and are doing an experiment to determine the optimum growth rate of this bacteria. You have inoculated five nutrient broths, and are incubating one broth at each of the following temp: 5C, 25C, 38C, 42C, and 55C
38C
You are studying a bacterium found in the normal intestinal flora of humans and most other mammals, and are doing an experiment to determine the optimum growth rate of this bacteria. You have inoculated five nutrient broths, and are incubating one broth at each of the following temperatures: 5oC, 25oC, 38oC, 42oC, and 55oC. At which temperature would you predict to see the optimum growth rate?
38oC
When a hypothesis has been thoroughly supported by long-term study and data, it is considered
A theory
Under what environmental conditions do yeast carry out fermentation?
Absence of oxygen
The purpose of staining cells on a microscope slide is to
Add contrast in order to see them better
What type of medium provides the best opportunity for growing and observing the morphology of isolated colonies?
Agar plates
You have placed cultures in an anaerobe jar, activated the gas pack, and sealed jar. Later in the day you check the jar and notice that the methylene blue strip is colorless. What does this indicate?
An anaerobic environment has been successfully established within the jar.
You have placed cultures in an anaerobe jar, activated the gas pack, and sealed the jar. Later in the day you check the jar and notice that the methylene blue strip is colorless. What does this indicate?
An anaerobic environment has been successfully established within the jar.
How is an antiseptic different from a disinfectant?
An antiseptic is used to remove or kill microorganisms on tissue, whereas a disinfectant is used to remove or kill microorganisms on inanimate objects.
Where would you predict an obligate anaerobe would grow in a tube of fluid thioglycollate medium?
At the bottom of the tube
Infectious lab waste is sterilized prior to disposal by
Autoclaving (steam autoclave)
What biosafety levels do most introductory microbiology students work with?
BSL-1
When completing a quadrant streak, when do you flame the loop?
Before you pickup a loopful of organisms from the original culture Before you streak quadrant one Before you streak quadrant two and three Before you return the loop to the receptacle
What is the most widely respected resource for bacterial identification?
Bergey's Manual of Determinative Bacteriology
Which is the most appropriate disposal for a swab used to culture your throat during lab?
Biohazard bag
Which of the flowing would be most appropriate for disposal for cultures on agar plates?
Biohazard bag or bin
Place these types of bacteria in order of their susceptibility to chemical disinfection, from least susceptible to most susceptible.
1. Bacterial endospores 2. Acid-fast bacteria 3. Gram-negative bacteria 4. Gram-positive bacteria
Match the following reagents with their role in the gram stain procedure 1. Safranin 2. Alcohol/acetone 3. Crystal violet 4. Gram's iodine
1. Counterstain 2. Decolonizer 3. Primary stain 4. Mordant
From the following list, select the scenarios from which using the isolation streak plate method would be used
1. Determining the bacteria from a patient nasal swab may be causing an infection 2. Determining the diversity of bacteria in a waster sample 3. Detecting the ability of an organism to breakdown specific sugars for energy production
Place in order the steps required to inoculate an agar plate from a broth culture
1. Flame inoculation loop 2. Remove cap from broth tube and flame mouth of tube 3. Obtain inoculate with loop 4. Flame mouth of tube, replace cap and place broth tube in test tube rack 5. Open plate lid and gently run loop across agar 6. Remove loop from plate, replace lid and flame loop
Which of the following is the correct order of steps needed to aseptically inoculate an agar plate from a broth culture?
1. Flame loop 2. Remove broth tube cap and flame mouth of tube 3.obtain inoculum 4. Flame mouth of tube and replace cap 5. Inoculate plate 6. Flame loop
Place in order the steps necessary to carry out proper isolation streak plate technique
1. Flame loop and obtain inoculum from mixed culture 2. Inoculate one half of an agar plate 3.flame loop, drag across slide of first inoculation on the agar plate and streak one third of the plate 4. Place loop in inoculated third of plate and streak the final third portion of the plate 5. Flame loop and replace plate lid
Place the steps of the Kirby Bauer method of antimicrobic sensitivity testing in the correct order.
1. Label a sterile Mueller-Hinton agar plate with organisms name and your name. 2. Obtain a dilute suspension of the organism in nutrient broth to use as the inoculum. 3. Using a swab, inoculate the agar plate uniformly by swabbing in three directions. 4. Dispense antibiotic disks onto the inoculated surface using sterile forceps or an automatic dispenser. 5. Tap down disks with sterile forceps. 6. Incubate for 18-24 hours at 35oC. 7. Measure diameters of zones of inhibition and compare zone diameters to interpretive charts and determine if S, I, or R.
Put these lenses in order they should be used when viewing a specimen with a bright field microscope
1. Low power lens 2. High dry lens 3. Low power lens
Put these lens in the order they should be used when viewing a specimen with a brightfield microscope
1. Low-power lens 2. High-dry lens 3. Oil immersion lens
match each sugar with the type of sugar they are 1. glucose 2. sucrose
1. Monossachride 2. dissacharide
Place the steps for preparing a simple stain in the correct order
1. Place a small drop of water on a clean microscope slide 2. Aseptically obtain a small loop of bacteria and mix with water 3. Evenly spread bacteria across slide to make a thin smear 4. Allow slide to air dry 5. Heat fix slide 6. Apply stain to slide for 1 to 2 minutes 7. Rinse stain off slide water 8. Blot slide dry with bibulous paper
Place the steps of gram staining in the correct order
1. Prepare slide for staining 2. Apply crystal violet 3. Apply iodine 4. Decolonize 5. Apply safranin 6. Rinse with water and blot dry
Please select all of the statements which are TRUE regarding isolated colonies
1. The colony results from a single cell or a cluster of cells multiplying into a visible mass. 2. Isolated colonies form on solid nutrient media. 3. Isolated colonies form in liquid nutrient media.
1. These organisms are likely to inhabit a compost pile this is actively compositing 2. The bacteria that grow in and on the human body are in this group 3. These organisms might grow in the superheated water near hydrothermal vents in the ocean floor 4. These organisms might be isolated from water pools on the surface of a glacier
1. Thermophile 2. Mesophile 3. Hyper thermophile 4. Psychrophile
What two factors increase the effectiveness of a disinfectant on microorganisms?
Concentration of disinfectant Time of exposure Material used to apply disinfectant Corrosiveness of the disinfectant
The patient asks how microbes from her body can grow in the lab. You explain that specimens are introduced to nutrient medium and that any growth of the microbe that appears after incubating the specimen is called the
Culture
Maria wants to know if the amount of sunlight in a garden affects the tomato size? Maria has 2 plants growing at the same time. Plant 1 is exposed to more light than plant 2. In this example, the measurement of size of the tomatoes is called_________
Dependent variable
The gram staining procedure is best described as a(n) ____ staining technique
Differential
A large zone of inhibition around a disk containing disinfectant generally indicates that the bacteria being tested is resistant to the disinfectant.
False
An agar plate that has colonies demonstrating multiple different morphologies is most likely a pure culture
False
As temperature decreases, membrane fluidity increases
False
Aseptic technique is only used when working with pure cultures isolation has already been achieved
False
Beverages are allowed in the lavatory as long as the containers are covered
False
Gram staining allows determination of the species of bacteria in a sample
False
In science experiments if my hypothesis is not proven as I expected, it's ok to change it after I see the results obtained
False
Inoculated tubes of fluid thioglycollate medium should be placed in an anaerobe jar during incubation.
False
It is important that the smear is thick in order to ensure that the stain will be retained on the slide
False
Many bacterial species can be identified by gram stain alone.
False
Observation of a Broth after transfer can show whether or not contamination has occurred
False
Petri dishes should be incubated with the lid side up
False
The application of a disinfectant to the lab bench ensures that the work area is sterile before the lab exercise is started
False
The coarse focus knob can be used to adjust the focus when using any of the objective lenses
False
The isolation steak plate technique is used to transfer a pure culture of bacteria from one medium to another
False
Treating the work area with disinfectant will kill all forms of microbes
False
Using a cell phone in a lab is permissible since it can be used for timing experiments
False
When doing the Schaeffer-Fulton method of endospore staining, safranin is used to stain the endospore and malachite green stains the vegetative cell.
False
When identifying an unknown bacterium, the acid fast staining procedure would be first differential stain used
False
When testing an organism with several different antibiotics, the antibiotic that produces the largest zone is the one that the microorganism is most sensitive to.
False
You may eat a snack in a lab as long as there are no bacterial cultures on your bench and you have thoroughly washed your hands
False
Zones of inhibitions are measured using metric system and measuring the diameter in cm units
False
Based on theory regarding blood agar, I can make the following hypothesis :
If I test Staphylococcus aureus, then the result for catalase test will be positive.
Maria wants to know if the amount of sunlight in a garden affects the tomato size. To answer this question Maria has 2 plants growing at the same time. Plant 1 is exposed to more light than plant 2. In this experiment, the amount of light is called________
Independent variable
No ferning of the vaginal fluid is detected, and you reassure your patient that her membranes have not ruptured. You explain that the laboratory technicians will use which five basic techniques (in order) to manipulate, grow, examine, and characterize any microorganisms present in the collected specimens?
Inoculation Incubation Isolation Inspection Identification
Please choose the method of antimicrobial susceptibility testing that involves measuring and evaluating zones of inhibition around antibiotic disks placed on a culture of bacteria prior to incubation.
Kirby-Bauer test
Which of the following should be worn at ALL times in lab?
Lab coat Closed toed shoes
Enzymes have which of the following characteristics?
N/A
In a catalase controlled experiment, the specificity of catalase can be shown by comparing
N/A
Polysaccharides are easier to ferment as compared to monossacharides
N/A
The active site is located on the substrate.
N/A
The shape of an enzyme determines its function.
N/A
Yeast can produce 2 ATP per molecule of glucose when using fermentation.
N/A
In which circumstance is food and/or beverage allowed in the laboratory?
Never
A bacterial isolate is subcultured to two blood agar plates, one of which is incubated in an anaerobe jar, and the other is incubated on a shelf in the incubator. After incubation, growth is observed on the plate from the anaerobe jar, but there is no growth incubated on the incubator shelf. Based on these results, how would this organism be categorized?
Obligate anaerobe
A bacterial species that can not tolerate the presence of oxygen and will only grow in the absence of oxygen is classified as a (n)
Obligate anaerobe
Why does culture age affect the result of a spore stain?
Older cultures are most likely to produce spores due to depleted nutrition
What is the correct way to open an agar plate to either remove a sample or to inoculate?
Open lid slightly on one side, in a calm-shell fashion
Compound microscopes are able to maintain proper focus of a specimen when moving from low power to higher power magnification due to a property known as_______
Parfocal
What is heat fixation?
Passing the slide through the flame of a burner several times after the smear has completely dried
Lab coats, gloves, face masks, and goggles are all examples of
Personal protective equipment
Gram negative bacteria stain _____ while gram positive bacteria stain ______
Pink or red.........purple
Listeria monocytogenes is a human pathogen, growing readily in the human body. It poses a problem in food storage, bc of its ability to grow in refrigerated foods, such as unpasteurized milk or deli meats. An organism that prefers moderate temp, such as 25-40C but is capable of growth at refrigerator temperature is known as a:
Psychotroph
Culturing of the sputum resulted in the growth of distinct colonies on the medium, and the technician informs you that further isolation by subculturing is now needed. You understand that this is accomplished by taking a bit of growth from an isolated colony and inoculating a separate medium, resulting in the production of a
Pure culture
Maria wants to know if the amount of sunlight in a garden affects the tomato size? Maria has 2 plants at the same time. Plant 1 is exposed to more sunlight than plant 2. For this experiment, when Maria measures the size of the tomato after growing it for 10 days, this is called:
Results
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
While using a lab photo atlas, a photo is listed as having a total magnification of 400x. Which of the following objectives was used in order to take the photo with a microscope that had 10x oculars?
The 40x objective
Imagine that you are observing an enzyme-catalyzed reaction in lab. Every time you add more enzyme, the reaction rate increases proportionally until the reaction rate suddenly levels off. No other chemicals were added, and no modifications were made in the experimental setting. Why do you think the reaction rate stopped increasing?
The molecules of substrate were all bound to enzyme.
What do the gram stain, and endospore stain have in common?
The outcome is based on cell differences
How is air contamination prevented when an inoculating loop is used to introduce or take a bacterial sample to/from an agar plate?
The plate lid is kept closed or lifted only slightly when inoculating
What would you predict would happen to the fermentation rate if you used yeast suspension that had not been swirled/mixed each time before it was dispensed into test tubes?
The reaction rate would be very low.
The coarse and fine focus knobs adjust the distance between
The stage and the objective lens
Which of the following statements about enzymes is FALSE?
The substrate binds to the enzyme with low specificity.
Mueller-Hinton agar plates are poured to a uniform thickness of 4mm. Zone size interpretive criteria are based on Mueller-Hinton plates of this thickness. If a plate had been poured that was 7 mm thick, how would this affect the size of the zones of inhibition?
The zones would be smaller
Taq polymerase is a DNA polymerase enzyme that demonstrate maximal activity at 72C. The organism from which this enzyme was isolated would most likely be classified as a:
Thermophile
When an inoculated plate (in particular steak plate) is placed inside incubator, it is important to invert because ________ (invert means with agar side up)
This position of the plate avoids condensation from dripping into the colonies
Where would you predict an facultative anaerobe would grow in a tube of fluid thioglycollate medium?
Throughout the tube
Why is antimicrobic sensitivity testing done?
To determine what antimicrobials would be most effective for treating the infection
During streak plate technique: what is the goal of this technique?
To promote growth of bacteria into single colonies on solid media
During streak plate technique: why is it necessary to flame the loop in between streaks?
To reduce # of bacteria from previous streaked area going into new streaked area
Match the objective used for the total magnification given
Total magnification of 400x =40x objective Total magnification of 1000x = 100x objective with immersion oil Total magnification of 100x= 10x objective Total magnification of 40x= 4x objective
Acid-fast cells stain pink-red while non acid fast cells stain blue
True
Fixed smears of specimens are required in order to perform the Gram stain and endospore stain on the specimens.
True
In order to be called a theory, a scientific idea has to undergo a great deal of testing
True
Maria wants to know if the amount of sunlight in a garden affects the tomato size? Maria has 2 plants growing at the same time. Plant 1 is exposed to more light than plant 2. For this experiment, we should use the same type and amount of soil and water to grow both pants (plant 1 and plant 2)
True
Once focus is achieved at one magnification, a higher-power objective lens can be rotated into position without fear of striking the slide
True
Only lint-free, optically safe tissue should be used to wipe off microscope lens
True
Opportunistic pathogens can be part of our normal flora that got out of balance
True
Patients samples need to be cultured and isolate single colonies, before carrying out specific testing to identify microbe
True
The degree of turbidity in a broth culture correlates to the amount of cell growth
True
Watches, bracelets, and rings should be removed prior to washing hands
True
What term is used to describe the cloudiness produced by bacterial growth in a tube of broth?
Turbidity
Microorganisms are found in nearly environment and are said to be ____
Ubiquitous
Which items can be discarded in a regular trash can?
Uncontaminated waste paper Wrappers from swabs of from disposable pipettes Used glass slides
Which of the following is used as a decolonizer for the endospore staining technique?
Water
How does smear preparation of cells from a liquid medium differ from preparation of cells from a solid medium?
Water is applied to the slide before emulsifying cells from a solid medium.
While observing a gram stain of staphylococcus aureus (a known gram positive organism) with a light microscope, you realize all of the cells stained red as if they are gram negative. After checking to make sure you stained the correct culture of S. Aureus, which of the following might best explain why the bacteria stained incorrectly?
While staining the mordant was not applied.
When testing bacteria for bile esculin, a positive result will be:___________
a dark/ (brown/black) color forms in the media after incubation with the specimen
In a catalase controlled experiment, the negative control can be shown by
a mixture of hydrogen peroxide and water.
Which of the following characteristics of a microorganism can be readily determined by directly observing the stained microorganism through a light microscope?
ability to ferment glucose shape and arrangement of cells Gram reaction presence of endospores presence of a capsule type of metabolism - aerobic or anaerobic
A sputum sample is ordered for microbial analysis in order to rule out the diagnosis of tuberculosis. Suspecting Mycobacterium tuberculosis may be the pathogen, you know that the laboratory technicians will perform which stain on the sample?
acid fast stain
The substrate binds at the enzyme's
active site
Media in slants and Petri dishes is solidified by the addition of __________________.
agar
Before heat fixation, a wet smear of bacterial cells on a slide must first be:
air dried
An increase in the concentration of substrate will result in
an increase in velocity of the reaction, until all of the enzyme is bound by substrate.
The goal of ______ technique is to minimized the contamination of both original and Newly inoculated cultures as well as to protect the laboratory worker from contamination
aseptic
Enzyme function is optimum
at specific pH and temperature ranges.
When bacteria cultured on MSA plates, turn the plate color to yellow, that means:_____________
bacteria can ferment mannitol
A disinfectant is used on your work surface
before the beginning of lab procedures, after all work is complete, and after any spill of live organisms.
When testing bacteria for catalase activity, a positive result will be:___________
bubbles appear after adding hydrogen peroxide
The products of fermentation by yeast are:_____
carbon dioxide (CO2) and ethanol (C2H6O) + 2ATP
The best test to differentiate between Staphylococcus species and Streptococcus species is:_______?
catalase
Enzymes act as
catalysts
UV light kills bacteria by:__________ (mechanism of action)
causing mutations on the DNA
Which of the following lenses does NOT affect the magnification of the specimen?
condenser lens
Which term refers to the introduction of unwanted microorganisms?
contamination
A substance used to support the growth of microbial life is referred to as a ______
culture medium
The advantage of using _________ media is that we can distinguish between two species of bacteria based on a difference in the physical appearance around the colony
differential
Which choice below briefly describes the Kirby-Bauer method of antimicrobic sensitivity testing?
disk diffusion
The use of the suffix "ase" on a word denotes a(n)
enzyme
select the situation for which UV treatment will work the best
f you want to decontaminate water that's in a shallow water treatment facility container
Some organisms exhibit flexibility in terms of their energy harvesting reactions. If provided with oxygen, they will obtain energy through aerobic respiration. If in an environment without oxygen, they will turn to fermentation to satisfy their energy needs. These organisms are classified as:
facultative aerobes
How is an inoculating loop or needle sterilized prior to use?
holding in the hottest part of the Bunsen burner flame until red-hot
An increase in enzyme or substrate concentration will
increase the amount of reaction.
The optimum condition for an enzyme
is where it works best.
Which of the following must happen prior to attempting to identify a bacterial species?
isolation of the bacteria in pure culture.
Select the body site that is free of normal flora (in other words: it's sterile, free of microbes)
liver
Enzymes speed up reactions by
lowering activation energy.
In the fermentation experiment by yeast, one can tell which sugar was fermented more effectively by_____?
measuring the air bubble produced inside respirometer
Both human pathogens and normal microbiota are typically classified as:
mesophiles
Cell shape, arrangement, presence of flagella, presence of endospores, and appearance of colonies on agar plates are all examples of _______________________ characteristics that can be helpful in the identification of bacteria.
morphological
A bacterial isolate is subcultured to two blood agar plates, one of which is incubated in an anaerobe jar, and the other is incubated on a shelf in the incubator. After incubation, growth is observed on the plate from the anaerobe jar, but there is no growth on the plate incubated on the incubator shelf. Based on these results, how would this organism be categorized?
obligate anaerobe
A bacterial species that cannot tolerate the presence of oxygen and will only grow in the absence of oxygen is classified as a(n):
obligate anaerobe
A given enzyme works on
one type of substrate
Consider the biochemical pathway below, where A, B, and C are substrates and products and E1 and E2 are the enzymes that catalyze the reactions. Enzyme 1 (E1) can utilize
only A as substrate.
The pink color in the top of the broth in an FTM tube indicates
presence of oxygen
Which of the following infectious agents is least likely to be damaged by UV exposure?
prions
What is the purpose of both cellular respiration and fermentation?
produce ATP
Enzymes are
proteins
To retrieve a sample from a culture tube with an inoculating loop, the cap of the tube is
removed and held with the fingers of the loop hand
A device that can be used to measure the rate of exchange of oxygen and carbon dioxide during fermentation is called a
respirometer
Where should glass slides, pipettes, and capillary tubes be disposed?
sharps container
UV light has ______ wavelengths than visible light waves, and its peak energy is at a wavelength of ______.
shorter; 254nm
Which of the following is essential for development of discrete, isolated colonies?
solid medium
Which of the following would be appropriately sterilized using UV radiation?
stainless steel surface in biological safety cabinet used for media preparation
Which of the following binds to the active site of an enzyme?
substrate
Enzymes act on _______ to generate ________.
substrates, products
_________ can change the active site of an enzyme and alter its function.
temperature and pH
When testing bacteria for coagulase activity, a positive result will be:___________
the media becomes solid (or forms a clot)
The pink color in the top of the broth in an FTM tube indicates
the presence of oxygen
As the concentration of an enzyme increases for a given substrate
the reaction rate increases similarly.
During streak plate technique: how can you tell that you obtained a successful result?
you will see single colonies after incubation
The clear area devoid of bacterial growth around an antiseptic or disinfecant disk is referred to as the
zone of inhibition
During the disinfectants' experiment we used ____________ as the control
water
Gram stain results from the patient specimen indicate a bacterial infection. From your microbiology course, you remember that this staining procedure involves
timed, sequential applications of crystal violet dye, iodine, an alcohol rinse, and a contrasting counterstain to the sample.
During experiments you did using UV light , one half of the culture was covered with a card before exposing to UV light. What was the purpose of covering that half?
to use that covered side as our control to prove that cells cultured were alive prior to exposure to UV light to demonstrate that cells died due to UV exposure and not something else
An inoculating loop or needle is sterilized in a flame or incinerator
until the entire wire is bright red