microbiology lab

Created by suncoastizn1 

Upgrade to
remove ads

D (1000X)

If you use a compound light microscope, a 2-micrometer bacterial cell is best seen at which magnification?
A) 10X
B) 100X
C) 400X
D) 1000X

D (multiplying)

The total magnification achieved by the microscope is calculated by _____ the magnification of the objective and the ocular lens.
A) subtracting
B) dividing
C) adding
D) multiplying

B (ocular; objective)

A compound microscope uses two lenses at once to magnify the image of a specimen. The _____ lens is found in the eyepiece and the _____ lens is found in the revolving nosepiece.
A) oil immersion; ocular
B) ocular; objective
C) high-power; low-power
D) scanning; oil immersion

B (micrometer)

Which of the following is the most convenient and appropriate unit for expressing the size of an average bacterial cell?
A) centimeter
B) micrometer
C) nanometer
D) millimeter

B (both the electron microscope and the light microscope use the same wavelegnths for illumination)

Which of the following statements about electron microscopy and light microscopy is FALSE?
A) The electron microscope has greater resolution than the light microscope.
B) Both the electron microscope and the light microscope use the same wavelengths for illumination.
C) Images produced by light microscopes can be in color, whereas images produced by electron microscopes are black and white unless they are artificially colored.
D) Electron microscopes can allow examination of viruses and internal cell structures, whereas light microscopes are limited to objects that are 0.5 micrometers and larger.

B (focus)

Related to focal length
A) Resolution
B) Focus
C) Contrast
D) Immersion Oil

C (to reduce the amount of light rays that are refracted away from the objective lens)

What is the purpose of adding a drop of mineral oil to the slide?
A) To increase the magnification
B) To lubricate the revolving nosepiece
C) To reduce the amount of light rays that are refracted away from the objective lens
D) To protect the lens from scratching

D (illuminator → condenser → specimen → objective lens/ocular lens)

Place these structures of the compound light microscope in the order that light passes through them on the way to the observer's eyes: (1) condenser, (2) ocular lens, (3) illuminator, (4) specimen, (5) objective lens.
A) illuminator → specimen → condenser → objective lens/ocular lens
B) ocular lens → condenser → specimen → illuminator → objective lens
C) illuminator → condenser → objective lens → specimen → ocular lens
D) illuminator → condenser → specimen → objective lens/ocular lens

D (immersion oil)

Enhances the resolving power of the microscope.
A) Focus
B) Resolution
C) Contrast
D) Immersion Oil

C (before and after lab work)

When should you disinfect your workbench? Choose the best answer.
A) When all lab work has been completed.
B) Any time you bring a liquid bacterial culture to your workbench.
C) Before and after lab work.
D) Only if a spill has occurred on your workbench.

B (placing culture tubes on their sides)

Which of the following actions should you AVOID in the laboratory?
A) Keeping a lab manual at your workspace.
B) Placing culture tubes on their sides.
C) Removing your gloves when you've completed the lab.
D) Putting away unnecessary items.

D (transfer microbes into your body)

Food and drinks are not allowed in the workspace primarily because they may __________.
A) distract you or others from lab work
B) clutter your workbench
C) spill
D) transfer microbes into your body

D (remove your gloves)

What should you do if you need to leave the laboratory temporarily in the middle of your work?
A) Put all contaminated materials in the appropriate area for proper disposal.
B) Decontaminate your work area.
C) Put away your lab manual.
D) Remove your gloves.

A (to prevent the potential transfer of microbes to you and your experiment)

Why should you decontaminate your work area prior to beginning lab work?
A) To prevent the potential transfer of microbes to you and your experiment.
B) So that you don't have to wear gloves during your experiments.
C) To remove any microscope oil on your bench top prior to working.
D) To coat the lab bench with disinfectant in case bacteria have spilled onto it.

C (remove your gloves, and properly dispose of them. Then put on a new pair.)

While working with a liquid bacterial culture, you get some culture on your gloves. Which of the following best describes what you should do?
A) Put on another pair of gloves over the contaminated pair.
B) Clean your gloved hands with disinfectant.
C) Remove your gloves, and properly dispose of them. Then put on a new pair.
D) Wipe your gloved hands with a paper towel. Dispose of the paper towel in the

A (heat the inoculating loop or needle with the Bunsen burner flame until it becomes red hot)

After using an inoculating loop or needle to transfer a culture from one medium to the next, what step should be taken next to avoid contamination?
A) Heat the inoculating loop or needle with the Bunsen burner flame until it becomes red hot
B) Wipe the inoculating loop or needle with a paper towel
C) Clean the inoculating loop or needle with soap and ethyl alcohol
D) Carefully place the inoculating loop or needle onto bench top

D (a technique that is free from contaminating organisms)

It is very important that microbiology students must develop aseptic techniques in order to prepare pure cultures. Which of the following statements properly defines aseptic technique?
A) A technique that involves antibiotic treatment
B) A technique free of any microorganism
C) A technique that involves treatment with ethyl alcohol
D) A technique that is free from contaminating organisms

D (specialized stain)

Which type of staining method would you use to determine endospore-forming cells from non-endospore-forming cells?
A) regular stain
B) simple stain
C) differential stain
D) specialized stain

B (a dye that carries a negative charged chromophore)

An acidic dye is:
A) a dye the carries no charge.
B) a dye the carries a negative charged chromophore.
C) a dye that carries no chromophore.
D) a dye that carries a positive charged chromophore.
E) a dye the carries both positive and negative charged chromophores

A (to increase the contrast and visibility of the specimen)

What is the purpose of staining samples?
A) To increase the contrast and visibility of the specimen
B) To kill the specimen
C) To see the specimen without the aid of a microscope
D) To make the specimen appear larger in the microscope

C (negative staining)

Which of the following would use the stain eosin?
A) acid-fast staining
B) endospore staining
C) negative staining
D) Gram staining
E) flagellar staining

A D E (strepto, diplo, staphylo)

What are the common arrangements of bacteria? (Select all that are correct. Be sure to select the appropriate scientific name. You lose points for choosing incorrectly or for not choosing a correct choice.)
A) Strepto
B) Cocci
C) Vibrios
D) Diplo
E) Staphylo
F) Bacillus
G) Spirillum

B (fixation differentiates that various cells being observed)

Before cells are stained, the specimen must be fixed. Fixing a specimen accomplishes all of the following EXCEPT which one?
A) Fixation attaches cells to the slide so they will not wash off during the staining process.
B) Fixation differentiates the various cells being observed.
C) Fixation kills the cells that are being stained for observation.
D) Fixation preserves cellular structure in the natural state with minimum distortion.

B (they are a basic stain and can be rinsed with water)

Which of the following is a characteristic of simple stains?
A) They stain specific structures of a bacterial cell AND can be rinsed with water.
B) They are a basic stain AND can be rinsed with water.
C) They can be rinsed with water.
D) They stain specific structures of a bacterial cell.
E) They are a basic stain.

B (the endospore stain is used to detect hard to stain endospores which are formed during adverse conditions to ensure organism's survival)

Which of the following staining procedures is matched with the principal use for that particular stain?
A) flagella stain used to detect capsules
B) The endospore stain is used to detect hard-to-stain endospores, which are formed during adverse conditions to ensure the organism's survival.
C) negative stain used to differentiate cell wall components
D) acid-fast stain for microbes with capsules

A C E F (vibrio, spirillum, cocci, bacillus)

Which of the following are bacterial SHAPES? (Select all that are correct. Be sure to select the appropriate scientific name. You lose points for choosing incorrectly or for not choosing a correct choice.)
A) Vibrio
B) Strepto
C) Spirillum
D) Staphylo
E) Cocci
F) Bacillus
G) Diplo

C (the colored portion to the dye)

. A chromophore is the:
A) transparent component of the dye
B) the part of the dye that does not bind.
C) the colored portion to the dye.
D) part of the dye that is not seen.
E) the part of the dye that is not used up.

D (a microbiologist is trying to determine whether an organism has flagella)

Consider the following situations, and determine when a simple stain should be used instead of a Gram stain.
A) A specimen is being examined in which the presence of multiple species of bacteria is suspected.
B) An unknown species of bacteria is being characterized and identified.
C) A wound specimen is being examined.
D) A microbiologist is trying to determine whether an organism has flagella.

A B C D

This is a multiple select question. Choose all of the following that are apprioprate:
A) Most microorganisms are transparent and staining allows the microbes to be visualized.
B) Staining allows the shape and size to be visualized.
C) Staining helps individual characteristics of a microorganism to be seen.
D) Staining allows the cell arrangements to be visualized.

B (is a dye that carries a positively charged chromophore)

A basic dye
A) is a dye that carries no charge.
B) is a dye that carries a positively charged chromophore.
C) is a dye that carries a negatively charged chromophore.
D) is a dye that carries both a positively and negatively charged chromophore.

D (streptococci)

Spherical shaped bacteria that divide and remain attached in chainlike patterns are called ________.
A) staphylococci
B) tetrads
C) spirochetes
D) streptococci

A (rich in degradative enzymes)

Gram-negative cells contain a periplasmic space that is ________.
A) rich in degradative enzymes
B) the site of protein synthesis
C) a site of endocytosis
D) abundant in photosynthetic pigments
E) filled with lysozyme

B (the contrast allows you to differentiate between gram negative and gram positive cells by observing the color of the organism)

Why is it important that crystal violet be a contrasting color to safranin?
A) Contrast allows the cells to stand out from the background.
B) The contrast allows you to differentiate between gram-negative and gram-positive cells by observing the color of the organism.
C) Crystal violet is attracted to the negatively-charged components of the cell wall; safranin is attracted to the positively-charged components of the cell wall.
D) Only safranin binds to the cell wall components of gram-negative cells.

B (colorless; purple)

If you forgot to add the counterstain to the mixed culture sample at the end of the staining procedure, gram-negative cells would appear __________ and gram-positive cells would appear __________.
A) purple; red or pink
B) colorless; purple
C) red or pink; purple
D) red or pink; colorless

D (the decolorization step)

What is the most critical step in the Gram staining procedure?
A) The application of the mordant
B) The counterstain
C) The primary stain
D) The decolorization step

D (it has teichoic acids)

Which of the following statements about a gram-negative cell wall is not true?
A) It contains endotoxin.
B) It maintains the shape of the cell.
C) It includes a thin layer of peptidoglycan.
D) It has teichoic acids.

The yeast and cheek slides will have some nucleated cells. The cheek smear should also have a variety of smaller, non-nucleated bacterial cells of different shapes. The plaque slide will have a variety of bacterial cells similar to those seen on the cheek slide.

Were the cell types the same in all three specimen sets: yeast, plaque, and cheek?
How were they similar? How were they different?

bacteriostatic agent

inhibit the growth of bacterial cells.

disinfection

the removal of pathogenic organisms such that infection or disease is prevented, it does not require the removal of all living cells

bactericidal agent

kill bacterial cells

steralization

the complete destruction or elimination of all viable organisms from an object

autoclaving

(steam under pressure or pressure cooker) at 121oC for 15 minutes is (15lbs/in2 pressure) good for sterilizing almost anything, but heat-labile substances will be denatured or destroyed.

dry heat

(hot air oven) at 160oC/2hours or 170oC/1hour is used for glassware, metal, and objects that won't melt.

incineration

burns organisms and physically destroys them. This method is used for needles, inoculating wires, glassware, et

filtration

involves the physical exclusion and removal of all cells in a liquid or gas, especially important to sterilize solutions which would be denatured by heat (e.g., antibiotics, injectable drugs, vitamins, etc.)

boiling

at 100oC for 30 minutes kills everything except some endospores. To kill endospores and therefore sterilize the solution, very long or intermittent boiling is required

chemical and gas toxic chemicals

such as formaldehyde, glutaraldehyde, and ethylene oxide can kill all forms of life in a specialized gas chamber.

irridation

usually destroys or distorts nucleic acids. Ultraviolet light is usually used to sterilize the surfaces of objects, although x-rays and microwaves are possibly useful.

obligate organism

required to meet the criteria in

aerobic organism

use oxygen in their metabolic pathways

facultative organism

can do with or without the criteria in question

anaerobic organism

do not and often cannot survive in the presence of oxygen

mesophile

bacteria that grow best at moderate temperatures. Their optimum growth temperature is between 25°C and 45°C. Most bacteria are mesophilic and include common soil bacteria and bacteria that live in and on the body

hyperthermophile

bacteria that grow at very high temperatures. Their optimum growth temperature is between 70°C and 110°C. They are usually members of the Archaea and are found growing near hydrothermal vents at great depths in the ocean Which type of organisms did you use in this lab - L acidophilus and S. epidermidis are both mesophiles

Psychrophile

cold-loving bacteria. Their optimum growth temperature is between -5°C and 15°C. They are usually found in the Arctic and Antarctic regions and in streams fed by glaciers

thermophile

heat-loving bacteria. Their optimum growth temperature is between 45°C and 70°C and are commonly found in hot springs and in compost heaps

B (inoculating needle)

What type of inoculating instrument is used to transfer a bacterial culture to an agar deep?
A) Inoculating loop
B) Inoculating needle
C) Pipette tip
D) None of the above

C (agar slant)

Which type of media should be inoculated using a zig-zag motion across the surface of the media?
A) Broth
B) Agar deep
C) Agar slant
D) All of the above

C (This creates an upward movement of airflow out of the tube that prevents contaminating organisms from traveling into the tube from the outside air)

After removing the cap from the culture tube it is recommended that the neck of the tube is briefly passed through the flame of the Bunsen burner. What is the purpose of this step?
A) Heating up the outer surface of the tube helps maintain optimal growth temperatures for the bacterial culture
B) This sterilizes the outer portion of the tube to prevent contamination from the surface
C) This creates an upward movement of airflow out of the tube that prevents contaminating organisms from traveling into the tube from the outside air
D) Heating up the outer surface of the tube helps loosen the bacteria from the media so they are easier to transfer

D (all of the above)

After incubating your culture for two days, you suspect that your culture is contaminated. Which method(s) would help you determine if this is the case?
A) Microscopic examination of cellular morphology
B) Differential staining techniques, such as the Gram stain
C) Subculture onto an agar plate
D) All of the above

D (binary fission)

Most bacteria divide by which method?
A) meiosis
B) fusion of gametes
C) mitosis
D) binary fission

B (disappearance of nuclear envelope)

Which of the following is NOT a step in bacterial cell division?
A) splitting apart of two new daughter cells
B) disappearance of nuclear envelope
C) replication of the genetic material
D) cell elongation

C (they are genetically identical to the parent)

Which of the following represent a true statement about the resulting new daughter cells?
A) Four new daughter cells result from one parental cell.
B) They are unable to divide.
C) They are genetically identical to the parent.
D) They share characteristics of both parental cells.

A (since the number of bacterial cells double after each round of replication the number of cells rapidly increases)

Which of the following characteristics is a hallmark of bacterial growth?
A) Since the number of bacterial cells double after each round of replication, the number of cells rapidly increases.
B) All daughter cells produced will be smaller than the parent.
C) After several rounds of division, the genetic diversity of the bacterial population will be very diverse.
D) Bacterial growth is fast because all bacterial cells undergo mitosis.

The two media used are nutrient broth and MRS broth. Lactobacillus acidophilus is a fastidious organism that requires special nutrients or growth factors to be grown in culture. MRS Broth is an enriched medium that provides the extra nutrients that L. acidophilus requires.

Which two types of media did you use in this experiment? Be specific about which type of bacteria you used for each type of medium and explain why the medium was used for that organism.

L. acidophilus are rod shaped, generally singular organisms. S. epidermidis are
spherically shaped and occur in clusters.

Describe your microscopic observations of the cultures. Use the V-scope for this. I am NOT asking for what the cultures look like to your naked eye.

D (enriched media)

Which of the following types of media contains one or more important growth factors (such as vitamins, amino acids, blood components) that are requred for the growth of fastidious organisms?
A) Selective Media
B) Differential Media
C) Complex Media
D) Enriched Media
E) Synthetic Media

D (selective media)

What type of media allows for the selection of particular microorganisms that may be present in a mixed culture
A) Enriched Media
B) Complex Media
C) Differential Media
D) Selective Media
E) Synthetic Media

C (differential medium)

What type of media allows for the separation of organisms based on some observable change in the appearance of the media or by an observable effect on the microbe?
A) Enriched Medium
B) Selective Medium
C) Differential Medium
D) Complex Medium
E) Defined Medium

D (complex medium)

What type of medium is composed of a mixture of proteins and extracts in which the exact amount of a particular amino acid, vitamin, or other nutrient is not known?
A) Enriched Medium
B) Selective Medium
C) Differential Medium
D) Complex Medium
E) Defined Medium

E (synthetic medium)

Which medium uses an exact amount of pure chemicals in its preparation?
A) Enriched Medium
B) Selective Medium
C) Differential Medium
D) Complex Medium
E) Synthetic Medium

A B C D E

Which medium uses an exact amount of pure chemicals in its preparation? (mutliple selection)

A) Enriched Medium
B) Selective Medium
C) Differential Medium
D) Complex Medium
E) Synthetic Medium

D (Crystal violet agar: inhibits the growth of gram-negative organisms, used to isolate gram-positive organisms)

Which of the following associations is INCORRECT regarding selective media?
A) Phenylethyl alcohol agar: inhibits the growth of gram-negative organisms, used to isolate gram-positive organisms
B) NaCl (sodium chloride) agar: inhibits the growth of a non-halophilic organisms, often used to isolate Staphylococcus
C) Crystal violet agar: inhibits the growth of gram-positive organisms, used to isolate gram-negative organisms
D) Crystal violet agar: inhibits the growth of gram-negative organisms, used to isolate gram-positive organisms

C (Phenol red permits the differentiation of bacteria based on their ability to ferment mannitol)

. What is the purpose of adding phenol red to mannitol salt agar?
A) Phenol red permits the differentiation of bacteria based on their ability to withstand high salt concentrations.
B) Phenol red inhibits the growth of gram-positive organisms.
C) Phenol red permits the differentiation of bacteria based on their ability to ferment mannitol.
D) Phenol red permits the differentiation of bacteria based on their ability to ferment lactose.

A (Eosin and methylene blue are dyes that precipitate on the surface of acid-producing colonies of enteric lactose fermenters, creating a metallic green sheen. )

What is the purpose of adding eosin and methylene blue to eosin-methylene blue agar?
A) Eosin and methylene blue are dyes that precipitate on the surface of acid-producing colonies of enteric lactose fermenters, creating a metallic green sheen.
B) Eosin and methylene blue are pH indicators that turn blue when lactose is fermented.
C) Eosin and methylene blue directly inhibit the growth of lactose nonfermenters.
D) Eosin and methylene blue are present to inhibit the growth of gram-negative organisms.

B (the organism is able to ferment mannitol)

You observe a yellow zone surrounding growth on mannitol salt agar. What does this indicate about the organism?
A) The organism is likely to be E.coli.
B) The organism is able to ferment mannitol.
C) The organism exhibits gamma hemolysis.
D) The organism is able to ferment lactose.

A (the organism is able to ferment lactose)

You observe red colored colonies growing on MacConkey agar. What does this indicate about the organism?
A) The organism is able to ferment lactose.
B) The organism is able to ferment mannitol.
C) The organism is likely Staphylococci.
D) The organism exhibits gamma hemolysis.

B (streptococci)

Enriched blood agar permits the demonstration of the hemolytic properties of what group of microorganisms?
A) Pseudomonas
B) Streptococci
C) Staphylococci
D) Escherichia

A (e. coli)

You observe colonies growing on EMB agar that are blue-black with a metallic green sheen. What species of bacteria is this likely to be?
A) E.coli
B) E.aerogenes
C) S.aureus
D) S.epidermidis

CFU

A measure of the number of viable organisms

TNTC

There are too many organisms to obtain an accurate count

TFTC

There are not enough organisms to obtain an accurate count

OD

The measure of the amount of light that passes through a sample

C (primary stain)

1. What is the purpose of crystal violet in the Gram's stain procedure?
A) counterstain
B) negative strain
C) primary stain
D) secondary stain
E) tertiary stain

A (E. coli)

Which of the organisms stained Gram-negative?
A) E. coli
B) S. epidermiduis
C) L. acidophilus
D) Saccharomyces cerevisiae

A C D (S. epidermidis, L. acidophilus, S. cervisiae)

Which of the organisms stained Gram-positive? Multiple selection.

A) S. epidermidis
B) E. coli
C) L. acidophilus
D) S. cerevisiae

A B C D

What purpose is served by a counterstain? Choose all correct answers. Incorrect answers will count against you.
A) stains those cells that were made invisible in the decolorization step
B) gives a contrasting color to the cells that did not retain the primary stain
C) allows interpretation of a differential staining procedure.
D) interpreted as a "negative" result for the structure that is detected by the primary stain.

A (purple)

For a Gram Positive organism, match each step of the staining procedure with the color that would be visible after that ste: Crystal Violet.
A. purple
B. pink
C. colorless

A (purple)

For a Gram Positive organism, match each step of the staining procedure with the color that would be visible after that step: Gram's Iodine
A. purple
B. pink
C. colorless

A (purple)

For a Gram Positive organism, match each step of the staining procedure with the color that would be visible after that step: decolorization
A. purple
B. pink
C. colorless

A (purple)

For a Gram Positive organism, match each step of the staining procedure with the color that would be visible after that step: Safranin
A. purple
B. pink
C. colorless

A (purple)

For a Gram Negative cell, match each step of the gram staining procedure with the color the cell would appear after that step: crystal violet
A. purple
B. colorless
C. pink

A (purple)

For a Gram Negative cell, match each step of the gram staining procedure with the color the cell would appear after that step: grams iodine
A. purple
B. colorless
C. pink

B (colorless)

For a Gram Negative cell, match each step of the gram staining procedure with the color the cell would appear after that step: decolorization
A. purple
B. colorless
C. pink

C (pink)

For a Gram Negative cell, match each step of the gram staining procedure with the color the cell would appear after that step: Safranin
A. purple
B. colorless
C. pink

D (cell wall)

Specifically, which microbial structure determines whether an organism is gram positive or gram negative?
A) plasma membrane
B) cytoplasm
C) flagella
D) cell wall
E) release of chromosomal material in the staining procedure

B (gram negative bacteria - negative stain)

Which of the following pairs is mismatched?
A) Iodine -- mordant
B) Gram-negative bacteria -- negative stain
C) Acid-alcohol -- decolorizer
D) Alcohol-acetone -- decolorizer

C (a basic dye)

The counterstain in the acid-fast stain is
A) An acid dye.
B) A mordant.
C) A basic dye.
D) A negative stain.
E) Necessary to determine acid-fast cells.

C (to prevent the crystal violet from leaving the cells)

The purpose of a mordant in the Gram stain is
A) To remove the simple stain.
B) To make the bacterial cells larger.
C) To prevent the crystal violet from leaving the cells.
D) To make the flagella visible.

D (a basic dye)

The counterstain in the Gram stain is
A) A negative stain.
B) An acid dye.
C) A mordant.
D) A basic dye.
E) Necessary to determine the Gram reaction.

A (compound light microscope)

Simple staining is often necessary to improve contrast in this microscope.
A) Compound light microscope
B) Phase-contrast microscope
C) Darkfield microscope
D) Fluorescence microscope
E) Electron microscope

D (kill the bacteria, affix the cells to the slide)

Bacterial smears are fixed before staining to
A) Kill the bacteria.
B) Affix the cells to the slide.
C) Make their walls permeable.
D) A and B.

C (alcohol-acetone)

Cells are differentiated after which step in the Gram stain?
A) Crystal violet
B) Safranin
C) Alcohol-acetone
D) Iodine

A (purple)

The appearance of gram-positive bacteria after addition of the first dye in the Gram stain.
A) Purple
B) Red or pink
C) Colorless
D) Brown

C (colorless)

The appearance of gram-negative bacteria after addition of the decolorizing agent in the Gram stain.
A) Purple
B) Red or pink
C) Colorless
D) Brown

A (purple)

The appearance of gram-positive bacteria after adding the counterstain in the Gram stain.
A) Purple
B) Red or pink
C) Colorless
D) Brown

B (cell structures are differentiated)

Which of the following is not accomplished by fixing cells to a slide?
A) Cells are killed.
B) Cell structures are differentiated.
C) Cell structures are preserved.
D) Cell structures such as the capsule are disturbed.
E) Cells are attached to the slide.

C (purple)

In the Gram stain, if the decolorizing step is deleted, gram-negative cells will appear ____at the completion of the staining procedure.
A) pink
B) blue
C) purple
D) green
E) unstained

B (in thick layers of peptidoglycan)

In the Gram stain, crystal violet remains in gram-positive cells after treatment with alcohol because crystal violet-iodine (CV-I) complexes are trapped
A) in the outer membrane.
B) in thick layers of peptidoglycan.
C) by endospores.
D) mycolic acid.
E) by flagella

D (a microbiologist is trying to determine whether an organism has flagellum)

Consider the following situations, and determine when a simple stain should be used instead of a Gram stain.
A) A specimen is being examined in which the presence of multiple species of bacteria is suspected.
B) An unknown species of bacteria is being characterized and identified.
C) A wound specimen is being examined.
D) A microbiologist is trying to determine whether an organism has flagella.

C ( Over time, gram-positive cells lose their ability to retain the crystal violet stain after decolorization.)

Why is it recommended that Gram staining be performed on young bacterial cultures (not older than 24 hours)?
A) Increased incubation times lead to increased risk of contamination.
B) Over time, gram-negative cells lose their ability to retain the crystal violet stain after decolorization.
C) Over time, gram-positive cells lose their ability to retain the crystal violet stain after decolorization.
D) Over time, gram-negative cells gain the ability to retain the crystal violet stain after decolorization.

D (colorless; purple)

If you forgot to add the counterstain to the mixed culture sample at the end of the staining procedure, gram-negative cells would appear __________ and gram-positive cells would appear __________.
A) red or pink; purple
B) red or pink; colorless
C) purple; red or pink
D) colorless; purple

A (The contrast allows you to differentiate between gram-negative and gram-positive cells by observing the color of the organism.)

Why is it important that crystal violet be a contrasting color to safranin?
A) The contrast allows you to differentiate between gram-negative and gram-positive cells by observing the color of the organism.
B) Only safranin binds to the cell wall components of gram-negative cells.
C) Crystal violet is attracted to the negatively-charged components of the cell wall; safranin is attracted to the positively-charged components of the cell wall.
D) Contrast allows the cells to stand out from the background.

C (rich in degradative enzymes)

Gram-negative cells contain a periplasmic space that is ________.
A) the site of protein synthesis
B) abundant in photosynthetic pigments
C) rich in degradative enzymes
D) filled with lysozyme
E) a site of endocytosis

C (rich in degradative enzymes)

Gram-negative cells contain a periplasmic space that is ________.
A) the site of protein synthesis
B) abundant in photosynthetic pigments
C) rich in degradative enzymes
D) filled with lysozyme
E) a site of endocytosis

biochemical tests

tests that microbiologists that use the biochemical profile of a particular microbe to differentiate between even closely related species.

B (mixed acids)

Choose all that apply:
What metabolic end product does the MR test for?
A) sugars
B) mixed acids
C) proteins
D) mixed bases
E) carbohydrates

A D (you should incubate longer, bacteria have not produced enough acid products)

Choose all that apply:
An orange color in the MR test indicates that
A) You should incubate longer.
B) It is a negative result
C) It is a positive result
D) Bacteria have not produced enough acid products
E) The bacteria do not produce acids

D (acetylmethylcarbinol (acetoin))

Choose all that apply:
What metabolic end product does the VP test for?
A) acid from fermentation
B) proteins
C) carbohydrates
D) acetylmethylcarbinol (acetoin).

The reagents that are added to the incubated tube, Barritt's Reagent A (a-napthol) and B (40% KOH), react with the acetoin and produce a thin colored layer at the top of the broth. If the tube is shook or jostled the layer will disperse into the broth and a false negative result will be observed.

Why do you need to be careful not to jostle the VP tube while waiting for the results to show?

C (S. epidermidis and E. coli)

Which of the organisms, if any, fermented glucose?
A) S. epidermidis
B) E. coli
C) S. epidermidis and E. coli
D) neither organism

C (both E. coli and S. epidermidis)

Which of the organisms, if any, produced measurable acidic byproducts?
A) E. coli
B) S. epidermidis
C) both E. coli and S. epidermidis

A (S. epidermidis)

Which organisms, if any produced catalase?
A) S. epidermidis
B) E. coli

B (S. epidermidis)

Which of the organisms, if any, produced acetoin?
A) E. coli
B) S. epidermidis
C) both E. and S. epidermidis
D) neither E. coli nor S. epidermidis

D (florescence microscope)

Match microscope with the description: uses a UV light source

A. compound light microscope
B. Phase-contrast microscope
C. Darkfield microscope
D. florescence microscope
E. electron microscope

E (electron microscope)

Match microscope with the description: simple staining is necessary to improve contrast, highest magnification and greatest resolution, observer does not look at image through a lens, does not use a light

A. compound light microscope
B. Phase-contrast microscope
C. Darkfield microscope
D. florescence microscope
E. electron microscope

B (phase-contrast microscope)

Match microscope with the description: used to see internal structures of a cells natural state

A. compound light microscope
B. Phase-contrast microscope
C. Darkfield microscope
D. florescence microscope
E. electron microscope

C (darkfield microscope)

Match the microscope with the description: produces an image of a light cell against a dark backround; internal structures not visible

A. compound light microscope
B. Phase-contrast microscope
C. Darkfield microscope
D. florescence microscope
E. electron microscope

0.001mm

How long is a micron?

B (basic dye)

If the chromophore (colored portion of the dye) resides in the positive ion and stains organism; methylene blue, crystal violet, and safranin

A. acidic dye
B. basic dye

A (acidic dye)

If the chromophore (colored portion of the dye) is in the negatively charged ion and leaves organism colorless; also called indirect or negative and is used to get a more accurate view of bacterial sizes, shapes, and arrangements; India ink, nigrosin, and Congo red.

A. acidic dye
B. basic dye

nutrient broth

is a liquid medium typically containing substrates for microbial growth such as pancreatic digest of casein, pancreatic digest of
soybean meal, sodium chloride, and water. After incubation, growth, the development of many cells from a few cells, may be observed as

C (pellicle)

A mass of organisms floats in or on top of the broth. Smaller masses or clumps of organisms that are dispersed throughout the broth form an even pattern called flocculent

A. turbidity
B. sediment
C. pellicle

A (turbidity)

The organisms appear as a general cloudiness throughout the broth.

A. turbidity
B. sediment
C. pellicle

B (sediment)

mass of organisms appears as a deposit at the bottom of the tube

A. turbidity
B. sediment
C. pellicle

A (environment)

Microbes from the ____________ grow best at room temperature.

A. environment
B. our bodies

B (our bodies)

Microbes from the ____________ grow best at physiological or body temperature.

A. environment
B. our bodies

E (selective media)

media allow for the selection of particular microorganisms that may
be present in a mixed culture. Selective media usually contain a component that enhances the growth of the desired organism or inhibits the growth of competing organisms.

A. Chemically defined (synthetic) media
B. Complex media
C. enrichment media
D. differential media
E. selective media

C (enrichment media)

medium contains some important growth factor (vitamin,
amino acid, blood component, or carbon source) necessary for the growth of fastidious organisms.

A. Chemically defined (synthetic) media
B. Complex media
C. enrichment media
D. differential media
E. selective media

B (complex media)

medium is composed of a mixture of proteins and extracts in which the exact amount of a particular amino acid, sugar, or other nutrient is not known.

A. Chemically defined (synthetic) media
B. Complex media
C. enrichment media
D. differential media
E. selective media

A (chemically defined/synthetic media)

medium, the exact amount of pure chemicals used to formulate the medium is known.

A. Chemically defined (synthetic) media
B. Complex media
C. enrichment media
D. differential media
E. selective media

C (crystal violet, grams iodine, decolorizer, safranin)

Put the steps of the Gram stain in order:
(1) Gram's iodine (2) crystal violet (basic) (3) decolorizer (ethyl alcohol and acetone) (4) safranin

A. 1, 4, 2, 3
B. 1, 2, 4, 3
C. 2, 1, 3, 4
D. 2, 1, 4, 3

A (Methyl Red (MR) test )

test used to identify bacteria based on their pattern of glucose metabolism; contains glucose, peptone, and a phosphate buffer

A. Methyl Red (MR) test
B. Voges-Proskauer (VP)

A (positive MR test)

Bacteria that produce mixed-acids as an end product of glucose fermentation overwhelm the buffer in the broth and cause a decrease in pH and turning media red

A. positive MR test
B. Negative MR test
C. Positive VP test
D. Negative VP test

B (negative MR test)

Bacteria that utilize other fermentation pathways and produce other, non-acidic end products do not cause a drop in the pH of the broth; broth turns yellow

A. positive MR test
B. Negative MR test
C. Positive VP test
D. Negative VP test

B (Voges-Proskauer (VP) test)

an assay for the presence of acetyl methyl carbinol (acetoin)

A. Methyl Red (MR) test
B. Voges-Proskauer (VP)

C (positive VP test)

After incubation of the organism in the MRVP broth, Barritt's Reagent A (a-napthol) and B (40% KOH) are added. The reagents react with acetoin, creating a maroon band at the top of the broth. If this occurs the test is:

A. positive MR test
B. Negative MR test
C. Positive VP test
D. Negative VP test

Please allow access to your computer’s microphone to use Voice Recording.

Having trouble? Click here for help.

We can’t access your microphone!

Click the icon above to update your browser permissions above and try again

Example:

Reload the page to try again!

Reload

Press Cmd-0 to reset your zoom

Press Ctrl-0 to reset your zoom

It looks like your browser might be zoomed in or out. Your browser needs to be zoomed to a normal size to record audio.

Please upgrade Flash or install Chrome
to use Voice Recording.

For more help, see our troubleshooting page.

Your microphone is muted

For help fixing this issue, see this FAQ.

Star this term

You can study starred terms together

NEW! Voice Recording

Create Set