Bacteriology Structure and Function Flashcards
What are some examples of distinguishing features in bacteria
Morphology
Staining characteristics
Growth conditions and requirements
Enzyme/ Toxin Production
Susceptability for phages/ antimicrobials
What are the four main categories of bacteria?
- Bacilli (rods)
- Cocci (spherical)
- Spirochaetes
- Vibrios (comma)
What is Gram Staining?
- distinguishes Gram-positive & Gram-negative
- based on retaining crystal violet staining + counterstaining
- heat fixation
- not usable with all bacteria
What is Diff-Quick Staining?
- rapid staining for morphology
- wet fixation
What are specific stainings?
- Ziehl-Neelsen (Mycobacteria)
- silver staining (spirochaetes)
What is the role of peptidoglycan?
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
How does Kwik Diff Staining?
- 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
What are the best type of growth media for non-fastidious organisms?
- Nutrient agar
- Mueller Hinton
What is the best type of growth media for enriched media for fastidious organisms?
- blood/serum agar (whole blood, lysed blood, serum)
- other supplements (electron acceptors, energy
sources)
What is the best type of growth media for selective media?
Supplemented plates, e.g antibiotics
What is the best type of growth media for differential use of antibiotics (fermentation of bacteria) ?
MacConkey Agar
What are the gas conditions required for bacteria growth?
Oxygen, Carbon Dioxide and Hydrogen
What are the other growth conditions required for bacteriology?
Temperature
* optimal growth temperature can vary
* may have limited temperature range
What are some biochemical tests for differentiation?
Oxidase, Catalase, Urease, Coagulase, Lactose fermentation, API-strips
What test do you use for gram-negative bacteria?
Oxidase test,
based on cytochrome C oxidase
What does the catalase test, test for?
It measures the conversion of H2O2 to H2O and O2
What does the coagulase test, test for?
It converts fibrinogen to fibrin
and is used to distinguish staphyloccocus species
What does Mac Conkey agar test for?
It selects for lactose fermenters
and senses pH changes with neutral red
Inhibits Gram + growth with bile and crystal violet
How are endospores formed?
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
