microbiology lab 5 bacterial smear and stain

which of the following apply to bacterial smears?

-bacterial smears provide scientist with the means to look at microorganisms -preparing smears disperses bacterial cells on a slide so that individual cells can be visualized under the microscope -preparation of bacterial smears is required for bacterial staining procedures

the purpose of heat fixation is to

1. adhere the organisms to the slide 2. inactivate microorganisms placed on the slide

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

1. cell wall 2. capsule 3. cell membrane

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

1. crystal violet 2. gram's iodine 3. decolorizer 4. safranin

which of the following represent consequences of incorrect performance of the decolorization step

1. decolorizing too briefly; false positive results 2.decolorizing for too long; removal of carbolfuchsin (primary stain) from all cells 3. decolorizing for too long; false negative results

endospores are difficult to stain due to which of the following?

1. endospores have a thick spore coat 2. endospores exclude dye

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

1. gram-positive cells retain the purple dye-mordant complex because of their thick layer of peptidoglycan 2. gram-negative cells are decolorized and stained by the pink/red secondary stain

if organisms are washing off of the slide during rinsing of the stain, which steps in the smear preparation may have been excluded?

1. heat fixation 2. air drying

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

1. help the bacteria spread evenly 2. reduce the tendency of the bacteria to stick together

a smear that is too thick will result in which of the following

1. inability to distinguish individual cell morphology 2.poor quality stain results

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

1. label the microscope slide 2. apply loopful of bacterial culture to slide 3. air dry 4. heat fix

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

1. label the slide with the name of the organism 2.apply loopful of sterile water to slide 3.add very small amount of organisms to water on slide 4. disperse organisms evenly over the center of the slide 5. air dry 6. heat fix

the acid-fast cell wall contains large amounts of mycolic acid. This glycolipid_________________

1. makes the cell wall resistant to decolorization with acid-alcohol 2. makes the cell wall less permeable to chemicals

which of the following would lead to an inability to identify the morphology of organisms using a simple stain

1. more than one organism in your sample 2. no organisms in sample 3. the organism has an acid-fast cell wall

which of the following are functions of the bacterial capsule?

1. protection 2. adherence

encapsulated organisms are difficult to directly stain because _______

1. the capsule does not react with most stains 2. the capsule is not permeable to stains

what is the purpose of a negative stain?

1. to visualize the bacteria 2. to visualize a capsule (if present) 3. to determine morphological characteristics of the specimen

which of the following errors during the simple stain procedure could lead to an inability to visualize bacteria on a slide

1. too many bacteria were applied during the smear preparation 2. slide was not rinsed after staining 3. bacteria were not fixed to the slide 4. stain was not applied for long enough

which of the following would be appropriate for choosing a sample to perform a smear preparation

1. use only a small amount of bacteria on the loop 2. use bacteria from an isolated colony

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

1. viruses 2. intracellular pathogens

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

1. you have a mixed population of bacteria in which some organisms are acid-fast and some are not 2.the primary stain was not allowed to stain long enough

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

1.mycolic acid makes the cells more difficult to stain 2.chemicals cannot readily penetrate the cell wall of these cells

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

30 seconds to 2 minutes

which of the following is/are the most appropriate ways to correctly label the name of an organism on a glass slide?

E. coli

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

Gram's iodine

what type of bacterial cell wall is composed of a thin layer of peptidoglycan and an outer membrane?

Gram-negative

what type of cell wall contains a thick layer of peptidoglycan and no outer membrane

Gram-positive

which occurs first in the endospore stain?

Staining the endospore

which of the following are disease caused by an acid-fast bacterium?

TB; leprosy

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

air drying of smeared bacterial cells

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

all of the above are commonly used

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

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

bacterial cells that are rod-shaped are called?

bacilli

which of the following bacterial genera are capable of producing endospores?

bacillus; clostridium

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

background

what is a bacterial smear?

bacteria spread on a slide

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

bacterial arrangements may be disturbed bacterial cells may show altered morphhology

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

blue

_______________ is the initial stain used in the acid-fast stain

carbolfuchsin

in the kinyoun acid-fast staining method, highly concentrated______________ is used to penetrate the cell wall and colorize acid-fast bacterial cells

carbolfuchsin

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

cellular arrangement cell morphology

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

clear

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

clear

if malachite green was omitted from the endospore stain, the endospores would appear _________ in color

clear

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

clear (colorless)

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

crystal violet

in a differential staining technique, a _________________ is used to remove the primary stain from the bacterial cell

decolorizer

the type of stain designed to show differences between various organisms or cellular structures is referred to as an _______________ stain, whereas a ___________ stain uses only one dye to stain all cell types

differential, simple

in order to withstand hostile conditions and facilitate survival, some bacteria produce resistant structures known as _____________

endospores

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

endospores would not take up stain

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

false

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

glycocalyx; capsule; slime layer

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

gram-negative organisms might not be visible

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

gram-negative; gram-positive

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

gram-positive and gram-negative organisms would stain pink

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

green

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

heat

which of the following describes the correct sequence of the Gram stain procedure?

heat-fixed slide; use of crystal violet, iodine, decolorizer, and safranin

which of the following is true regarding proper heat fixation?

heating too briefly may result in bacteria not adhering to the slide

__________________ is used to stain the endospore in the endospore staining procedure.

malachite green

___________________ is used to stain the endospore in the endospore staining procedure.

malachite green

the counterstain used in the acid-fast stain is_______________

methylene blue

a chemical that fixes dye in or on cells by forming an insoluble compound is referred to as an________?

mordant

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

mycolic acid

Gram-________ cell walls contain a thin layer of peptidoglycan whereas Gram-__________ cell walls contain a thick layer of peptidoglycan

negative; positive

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

pink

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

pink

if you decolorize for more than 30 seconds, gram-positive organisms will most likely appear ______________ in color

pink

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

pink/red

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

pink/red

Gram-negative cells appear _________ after gram staining whereas gram-positive cells appear_________

pink; purple

the first dye applied in a differential staining technique is referred to as the _____________stain

primary

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

red

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

remember that the secondary stain and the counterstain are the same thing

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

ribosomes cell membrane

_________________ is used to stain the vegetative cells in the endospore staining procedure

safranin

the name of the counterstain, or secondary stain, typically used in the Gram stain technique is _________

safranin

in a differential staining technique, the stain that is used after the decolorization step is called the counterstain, or______________stain

secondary

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

smear

spherical cells arranged in a chain are called?

streptococci

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

the bacteria are non-acid fast

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

the endospore coat

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

the heating should be very brief. passing the slide through the flame for 3-5 seconds is enough

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

the non-acid-fast organisms on the slide

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

the thickness of the peptidoglycan layer

stains are commonly used for all of the following except?

the treatment of disease

which of the following apply to endospores?

they are used for surviving adverse environmetal conditions

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

this ensures the optimal preservation of the bacterial morphology

what is the purpose of the smear preparation?

to allow for visualization of individual bacteria

what is the purpose of the Gram staining technique?

to characterize unknown bacteria

what is the purpose of a simple stain?

to determine cell shape and arrangement of the specimen to visualize bacteria

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

true

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

true

which of the following are characteristics of simple stains?

used to visualize morphology of bacteria used to identify cellular arrangement of bacteria

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

using the loop, you dispense the bacterial into the water drop on the microscope slide

how do you smear a bacterial culture onto the microscope glass slide

using the loop, you spread the bacteria onto the center of the microscope slide

an ___________ is a metabolically active and growing cell.

vegetative cell

bacterial cells that are curved rods or comma-shaped are called______________ whereas helical bacteria are referred to as spirilla or spirochetes

vibrio

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

visualization of microorganisms differentiation of microorganisms

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

wrights stain