Bacteriology Structure and Function

Question 1

What are some examples of distinguishing features in bacteria

Answer 1

Morphology
Staining characteristics
Growth conditions and requirements
Enzyme/ Toxin Production
Susceptability for phages/ antimicrobials

Question 2

What are the four main categories of bacteria?

Answer 2

• Bacilli (rods)
• Cocci (spherical)
• Spirochaetes
• Vibrios (comma)

Question 3

What is Gram Staining?

Answer 3

• distinguishes Gram-positive & Gram-negative
• based on retaining crystal violet staining + counterstaining
• heat fixation
• not usable with all bacteria

Question 4

What is Diff-Quick Staining?

Answer 4

• rapid staining for morphology
• wet fixation

Question 5

What are specific stainings?

Answer 5

• Ziehl-Neelsen (Mycobacteria)
• silver staining (spirochaetes)

Question 6

What is the role of peptidoglycan?

Answer 6

Peptidoglycan gives rigidity to the bacterial cell
It assists in preventing phagocytosis
It has pyrogenic properties (causes fever)
Can be degraded by the enzyme lysozyme

Question 7

How does Kwik Diff Staining?

Answer 7

• Place drop on slide, let air dry briefly
• Place in fixative for a few seconds
• Place in solution 1 for a few seconds
• Place in solution 2 for a few seconds
• (Optional): wash with distilled water
• Let excess liquid drain after each step

Question 8

What are the best type of growth media for non-fastidious organisms?

Answer 8

• Nutrient agar
• Mueller Hinton

Question 9

What is the best type of growth media for enriched media for fastidious organisms?

Answer 9

• blood/serum agar (whole blood, lysed blood, serum)
• other supplements (electron acceptors, energy
  sources)

Question 10

What is the best type of growth media for selective media?

Answer 10

Supplemented plates, e.g antibiotics

Question 11

What is the best type of growth media for differential use of antibiotics (fermentation of bacteria) ?

Answer 11

MacConkey Agar

Question 12

What are the gas conditions required for bacteria growth?

Answer 12

Oxygen, Carbon Dioxide and Hydrogen

Question 13

What are the other growth conditions required for bacteriology?

Answer 13

Temperature
* optimal growth temperature can vary
* may have limited temperature range

Question 14

What are some biochemical tests for differentiation?

Answer 14

Oxidase, Catalase, Urease, Coagulase, Lactose fermentation, API-strips

Question 15

What test do you use for gram-negative bacteria?

Answer 15

Oxidase test,
based on cytochrome C oxidase

Question 16

What does the catalase test, test for?

Answer 16

It measures the conversion of H2O2 to H2O and O2

Question 17

What does the coagulase test, test for?

Answer 17

It converts fibrinogen to fibrin
and is used to distinguish staphyloccocus species

Question 18

What does Mac Conkey agar test for?

Answer 18

It selects for lactose fermenters
and senses pH changes with neutral red
Inhibits Gram + growth with bile and crystal violet

Question 19

How are endospores formed?

Answer 19

Cytoplasmic membrane inavginates to form a forespore
The cytoplasmic membrane grows and engulfs the forespore within a second membrane
a cortex of calcium is deposited between the membranes
spore coat then forms around the endospore
maturation of the endospore is complete
endospore is then released