UAMS MICROBIOLOGY EXAM #1 QUESTIONS &
ANSWERS
Gram stain, culture, organism identification, and antimicrobial susceptibility. - Answers -
In the health care system, the physician consults with the patient and retrieves a
specimen. The specimen is then sent to the lab, a report is generated, and the report is
sent to the physician. What are the 4 things included in the report from the micro lab?
Specimen collection. It is a tube closed on the bottom and open at the top with swabs
inserted into the culturette container. - Answers -What is a culturette used for?
Collect the specimen with a culturette tube, plate it using either an agar or broth
medium, incubate the culture, and then ID. Determine antimicrobial susceptibility and
report results. - Answers -What is the complete procedure done by the lab for collecting
and then identifying an organism?
Coccus, coccobacillus, vibrio, bacillus, spirillum, and spirochete. - Answers -What are
the different morphologies of bacteria?
Coccus (one single colony), diplococci (two colonies), staphylococci (multiple colonies
in a triangle shape), streptococci (multiple colonies in a linear row), sarcina (multiple
colonies that can be on top of one another in a square shape), and tetrad (four colonies
in a square). - Answers -What are the different bacterial arrangements for cocci?
Rod shaped. The genus (Bacillus anthracis). Single bacillus, diplobacilli, streptobacilli,
and palisade (rods laid side by side, forming a fence-like appearance; can also be V-
shaped). - Answers -What does bacillus or bacilli refer to? What about Bacillus? What
are the bacilli arrangements?
Bacteria that is capable of altering its morphology to take on many different shapes. -
Answers -What does the term pleomorphic refer to? Ex. Pleomorphic bacilli
Spores are cells with very thick walls that can survive many extremes, allowing a
bacterium protection in order to preserve its genetic material. - Answers -What are
spores and what do they allow a bacterium, such as bacilli with spores?
Filamentous and fusiform. - Answers -What are the two different forms of bacilli rods?
Hans Christian Gram. Crystal violet, iodine, decolorizer, and safranin. The cell wall
structure of the bacteria is what determines if it is gram pos or neg. The thick
peptidoglycan layer on gram pos MOs retains the crystal violet-iodine complex. On
gram neg MOs, there is only a thin layer of peptidoglycan under a layer of lipids. The
lipid layer retains the stain and the decolorizer then dissolves the lipid layer, removing
the crystal violet-iodine complex. - Answers -Who invented the Gram stain and staining
, method? What are the reagents involved? How is Gram stain able to work? What
makes some bacteria gram pos and others neg?
Safranin. Once the decolorizer dissolves the lipid layer holding the crystal violet-iodine
complex, the safranin is able to stain the thin peptidoglycan layer underneath, causing
the bacteria to appear pink. The pink bacteria can then be identified as Gram neg. -
Answers -What is the counter stain that is used alongside Gram stain to identify the
Gram neg bacteria? How does this work?
Cells from a culture are taken and spread over a thin area of a slide and then heat fixed.
The smear doesn't need to be too thin or too thick, otherwise it will be unable to be read
properly. Smears are heat fixed using a bunsen burner, an electric incinerator, or
methanol. This is done to kill the bacteria on the slide, prevent bacteria from washing off
the slide, and allowing the smear to take up stain better. - Answers -What is smear?
What is important when preparing a smear? How are smears heat fixed and why?
Place the slide on a staining rack and cover the smear with crystal violet solution. Let
stand for 30-60 seconds. Rinse with tap water to remove the crystal violet, then shake
off excess water. Cover the smear with Gram's iodine and let stand for 30-60 seconds.
Rinse with water, then shale off excess. Decolorize the smear with acetone-alcohol and
rinse with water as soon as the purple/blue color no longer runs off the slide. *Be careful
to not over or under decolorize* Shake off excess water and counterstain with safranin
for 30 seconds, rinse with water, and dry slide by air or by blotting. - Answers -What is
the Gram staining procedure?
Gram neg cells such as human cells will appear washed out and gram pos bacteria will
appear gram neg or partially stained. Gram neg cells such as human cells will appear
dark red / purple and other gram neg bacteria appear gram pos. - Answers -What will
happen is the decolorizer is left on too long? What about under-decolorized?
Damaged cells are a potential problem when looking at older culture, they will not take
up stain. This can be due to antibiotics. Overheating a slide distorts cells from their
normal shape, causing them to look weird when viewing. Improper reagent use can be a
source of error when one is omitted or they are used in the wrong order. Excessive
rinsing can wash out the crystal violet or crystal violent iodine complex away, Prolonged
counterstaining might cause the crystal violet complex to be leached from the Gram pos
MOs. - Answers -How will damaged cells pose as a source of error when staining?
How does overheating a slide pose as a source of error? What about improper reagent
use? What about excessive rinsing and prolonged counterstaining?
Media is used to culture specimens, isolate bacteria, biochemicals used for
identification, and used for antibiotic susceptibility.
Liquid broth, semi-solid agar (0.3-0.5%), agar slants, and solid agar (1-2%).
Polysaccharide is the main component, melting at 100 C and staying liquid until 45-50
C. Different agars are created by using different amounts of polysaccharide. Semi-solid
has less, whereas solid has more. - Answers -Why is media used in microbiology?
ANSWERS
Gram stain, culture, organism identification, and antimicrobial susceptibility. - Answers -
In the health care system, the physician consults with the patient and retrieves a
specimen. The specimen is then sent to the lab, a report is generated, and the report is
sent to the physician. What are the 4 things included in the report from the micro lab?
Specimen collection. It is a tube closed on the bottom and open at the top with swabs
inserted into the culturette container. - Answers -What is a culturette used for?
Collect the specimen with a culturette tube, plate it using either an agar or broth
medium, incubate the culture, and then ID. Determine antimicrobial susceptibility and
report results. - Answers -What is the complete procedure done by the lab for collecting
and then identifying an organism?
Coccus, coccobacillus, vibrio, bacillus, spirillum, and spirochete. - Answers -What are
the different morphologies of bacteria?
Coccus (one single colony), diplococci (two colonies), staphylococci (multiple colonies
in a triangle shape), streptococci (multiple colonies in a linear row), sarcina (multiple
colonies that can be on top of one another in a square shape), and tetrad (four colonies
in a square). - Answers -What are the different bacterial arrangements for cocci?
Rod shaped. The genus (Bacillus anthracis). Single bacillus, diplobacilli, streptobacilli,
and palisade (rods laid side by side, forming a fence-like appearance; can also be V-
shaped). - Answers -What does bacillus or bacilli refer to? What about Bacillus? What
are the bacilli arrangements?
Bacteria that is capable of altering its morphology to take on many different shapes. -
Answers -What does the term pleomorphic refer to? Ex. Pleomorphic bacilli
Spores are cells with very thick walls that can survive many extremes, allowing a
bacterium protection in order to preserve its genetic material. - Answers -What are
spores and what do they allow a bacterium, such as bacilli with spores?
Filamentous and fusiform. - Answers -What are the two different forms of bacilli rods?
Hans Christian Gram. Crystal violet, iodine, decolorizer, and safranin. The cell wall
structure of the bacteria is what determines if it is gram pos or neg. The thick
peptidoglycan layer on gram pos MOs retains the crystal violet-iodine complex. On
gram neg MOs, there is only a thin layer of peptidoglycan under a layer of lipids. The
lipid layer retains the stain and the decolorizer then dissolves the lipid layer, removing
the crystal violet-iodine complex. - Answers -Who invented the Gram stain and staining
, method? What are the reagents involved? How is Gram stain able to work? What
makes some bacteria gram pos and others neg?
Safranin. Once the decolorizer dissolves the lipid layer holding the crystal violet-iodine
complex, the safranin is able to stain the thin peptidoglycan layer underneath, causing
the bacteria to appear pink. The pink bacteria can then be identified as Gram neg. -
Answers -What is the counter stain that is used alongside Gram stain to identify the
Gram neg bacteria? How does this work?
Cells from a culture are taken and spread over a thin area of a slide and then heat fixed.
The smear doesn't need to be too thin or too thick, otherwise it will be unable to be read
properly. Smears are heat fixed using a bunsen burner, an electric incinerator, or
methanol. This is done to kill the bacteria on the slide, prevent bacteria from washing off
the slide, and allowing the smear to take up stain better. - Answers -What is smear?
What is important when preparing a smear? How are smears heat fixed and why?
Place the slide on a staining rack and cover the smear with crystal violet solution. Let
stand for 30-60 seconds. Rinse with tap water to remove the crystal violet, then shake
off excess water. Cover the smear with Gram's iodine and let stand for 30-60 seconds.
Rinse with water, then shale off excess. Decolorize the smear with acetone-alcohol and
rinse with water as soon as the purple/blue color no longer runs off the slide. *Be careful
to not over or under decolorize* Shake off excess water and counterstain with safranin
for 30 seconds, rinse with water, and dry slide by air or by blotting. - Answers -What is
the Gram staining procedure?
Gram neg cells such as human cells will appear washed out and gram pos bacteria will
appear gram neg or partially stained. Gram neg cells such as human cells will appear
dark red / purple and other gram neg bacteria appear gram pos. - Answers -What will
happen is the decolorizer is left on too long? What about under-decolorized?
Damaged cells are a potential problem when looking at older culture, they will not take
up stain. This can be due to antibiotics. Overheating a slide distorts cells from their
normal shape, causing them to look weird when viewing. Improper reagent use can be a
source of error when one is omitted or they are used in the wrong order. Excessive
rinsing can wash out the crystal violet or crystal violent iodine complex away, Prolonged
counterstaining might cause the crystal violet complex to be leached from the Gram pos
MOs. - Answers -How will damaged cells pose as a source of error when staining?
How does overheating a slide pose as a source of error? What about improper reagent
use? What about excessive rinsing and prolonged counterstaining?
Media is used to culture specimens, isolate bacteria, biochemicals used for
identification, and used for antibiotic susceptibility.
Liquid broth, semi-solid agar (0.3-0.5%), agar slants, and solid agar (1-2%).
Polysaccharide is the main component, melting at 100 C and staying liquid until 45-50
C. Different agars are created by using different amounts of polysaccharide. Semi-solid
has less, whereas solid has more. - Answers -Why is media used in microbiology?
