Microbio Assignments

BIOL 2230 McGraw Hill

After 48 hours of incubation, the surface of a starch agar plate growing a test bacterium is flooded with iodine. The entire plate turns into a blue-black color. This indicates that

the test organism did not hydrolyze starch

An organism that hydrolyzes starch possesses the enzyme

amylase

What is an endospore?

A dormant structure formed by bacteria in response to nutrient depletion

Why is endospore staining important?

It helps in identifying the few medically important genera that produces endospores

When is sporulation initiated by spore-forming bacteria?

When nutrients are depleted or conditions become adverse

When spore formation begins, the vegetative cell is referred to as the

mother cell

The developing spore is surrounded by

the membrane of the mother cell.

The cortex is formed from

peptidoglycan

In the next phase of spore formation, _________ enters the cortex and _________ leaves the cortex

calcium; water

In the final step of spore formation, a _________ coat forms around the cortex

protein

Characteristics of Vegetative Cells

• actively metabolizing

• stain w/ safranin

• high water content

Characteristics of Endospores

• stain w/ malachite green

• require autoclave for destruction

• formed when conditions become unfavorable

• heat is mordant to facilitate staining of these

• highly resistant to heat and chemicals

Characteristics of Gram Stain

• does not require heat to be used in staining process

• differentiates cells based on thickness of peptidoglycan layer

• a chemical is used as a mordant

• result is purple and red/pink cells

Characteristics of Acid-Fast Stain

• may or may not require heat (depending on the primary stain used)

• uses basic fuchsin, acid-alcohol, and methylene blue

• important diagnostic tool in Mycobacterium infections

• differentiates cells w/ high lipid content in cell wall

Characteristics of Spore Stain

• uses malachite green

• requires heat for penetration of primary stain

• distinguishes between active metabolic cells and dormant structures

Blood agar is an enriched medium. Which of the following is the best description of what this term means?

It contains nutrients and growth factors to support fastidious organisms.

You have just isolated bacteria from the back of your throat. Before culturing on blood agar, how could you most quickly determine if you have streptococci or staphylococci?

Caralase test

What is the role of hemolysins found in some bacteria?

Breaking up of red blood cells

which of the above represents alpha hemolysis?

c

which of the above represents gamma hemolysis?

b

which of the above represents beta hemolysis?

a

review

review

Select the pathogen from the genus Streptococcus that correctly represents the most serious pathogen of this group.

Group A beta-hemolytic S. pyogenes

What test will differentiate Enterococcus from Streptococcus bovis?

Growth in 6.5% NaCl

Which of the following must be used to perform a CAMP test? 

all of the options

A beta-hemolytic streptococcus has been isolated from a vaginal specimen collected from a pregnant woman during her third trimester. The following are the test results on this isolate:

What is the most likely identification of this isolate?

Beta-hemolytic streptococcus group B