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KN-Micro Block 1 > Bacterial Structure and Classification > Flashcards

Bacterial Structure and Classification Flashcards

1
Q

What are round bacterium called? Rod shaped?

A 
cocci = round
bacilli = rod
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2
Q

What would a chain of round bacterium be called? Sets of two?

A 
streptococci = chain
diplococci = doublets
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3
Q

What would a grape-like cluster of cocci be called?

A

staphylococci

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4
Q

What are comma shaped bacterium called

A

vibria

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5
Q

What are corkscrew shaped bacterium called?

A

spirilli and/or spirochetes

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6
Q

Describe the difference between prokaryotic DNA and eukaryotic.

A

Prokaryotic DNA is usually found in a single, circular chromosome that lacks introns and histones

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7
Q

What are bacterial cell walls composed of? If they are Gram + what is up to 50% of it composed of?

A

peptidoglycan.

Gram + cell walls contain up to 50% teichoic acid or lipoteichoic acid

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8
Q

Which has a tightly woven, cross-linked cell wall: gram + or -

A

Gram + is tightly woven and cross linked

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9
Q

Which type of bacterium has two cellular membranes: gram + or -

A

Gram - bacteria have an inner cell membrane, then the cell wall, then an outer cell membrane

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10
Q

A cellular membrane is found to lack sterols. Is it likely prokaryotic or eukaryotic?

A

prokaryotic cytoplasmic membranes lack sterols, whereas eukaryotic membranes rely on them.

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11
Q

Which have larger ribosomes: prokaryotes or eukaryotes?

A

eukaryotes

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12
Q

What purposes do pili serve?

A

they allow ‘sexual’ transmission of genes between bacteria during conjugation
and
allow bacteria to anchor to hosts

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13
Q

What are capsules composed of?

A

polysaccharide or polypeptides

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14
Q

What unique ability do some Gram + bacteria have that allows them to survive extremely harsh conditions for expansive lengths of time?

A

generation of spores: dehydrated, dormant forms that allow potential pathogens to survive for up to centuries in harsh conditions. Ex: anthrax

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15
Q

What is the region between the two membranes of a gram - bacteria called? What lies within this region?

A

Periplasmic space. The peptidoglycan cell wall layer and a host of degradative enzymes that can potentially destroy antibiotics.

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16
Q

Does the outer membrane of a Gram - bacteria have a charge? If so, what is it and what is its purpose?

A

Negative charge that helps these bacteria evade phagocytosis, hinder antibiotic uptake, and avoid action of complement.

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17
Q

How to bacteria uptake nutrients through their membranes and cell walls?

A

proteins called porins

18
Q

If LPS (lipopolysaccharide) is found in a bacteria what do you know?

A

That it is Gram -.

19
Q

What pathologically important things does LPS contain?

A 
Lipid A (aka endotoxin) which illicits cytokine reactions and sepsis
 and O-antigen which is important for serotyping some species
20
Q

Describe how a Type II system works in secreting bacterial compounds.

A

In Type II systems, proteins are secreted from the cytoplasm into the periplasm. Once there, they are secreted across the outer membrane.

21
Q

Which protein secretion system is found ONLY in pathogenic bacterium? Describe it.

A

Type III (molecular syringe). Injects proteins from cytoplasm of bacteria, across both membranes and directly into the cytoplasm of the attached host animal cell.

22
Q

Which protein secretion system is a member of the ABC (ATP binding cassette) and found in all Gram negative bacteria? Describe it.

A

Type I. proteins are secreted directly into the extracellular environment by the ATP binding cassette transporters

23
Q

What is peptidoglycan composed of?

A

repeating disaccharides of NAG and NAM to form long chains called Transglycosylase.

A pentapeptide is attached to each NAM and these pentapeptides cross-link to eachother to form the sugar backbones with the help of transpeptidase and carboxypeptidase enzymes (penicillin binding proteins).

24
Q

What is the target of penicillin and many antimicrobials in gram + bacteria?

A

The terminal D-alanine pair in the pentapeptides.

25
Q

Where does bacterial cell wall assembly begin?

A

In the cytoplasm

26
Q

What does lysozyme do? Where is it often present?

A

It is a natural defense that targets the bond between NAM and NAG. It is a glycosylase that hydrolyzes the bonds.
It is often present in tears, saliva and in lysosomes of phagocytic cells.

27
Q

What was the first Beta-lactam (B-lactam)?

A

penicillin G.

28
Q

What is B-lactam?

A

series of antibiotics based off the B-lactam ring, which structurally resembles the D-alanine terminal pair of the pentapeptide side chains. Because of this, they bind to the necessary transpeptidases and prevent cross-linking.

29
Q

How can a bacteria be B-lactam resistant?

A

It can produce B-lactamases that cleave the B-lactam ring or it can produce mutated transpeptidases that no longer bind B-lactams.

30
Q

How does a bacteria become Vancomycin resistant?

A

Produce D-alanine D-lactone instead of the D-ala D-ala double. This pair is recognized by transpeptidases but not by vacomycin.

31
Q

What cleaves cell walls at sites for new subunit insertion?

A

bacterial autolysins (Very similar to lysozymes)

32
Q

Why can’t normal Gram staining be used for Mycoplasma? What about Chlamydia?

A

Mycoplasma are the smallest free-living organisms and they lack a cell wall.

Chlamydia lacks peptidoglycan even though they have the double membrane of Gram -.

33
Q

What would you expect from a Gram stain test of Mycobacterium?

A

It wouldn’t work because the cell walls of that genus have a waxy coat of mycolic acid that interferes with staining. Once stained with another stain, acid removers will not remove it so they are called ‘acid-fast’

34
Q

What process do anaerobes use for metabolism?

A

fermentation

35
Q

What is the name for a bacteria that can live with or without oxygen?

A

facultative anaerobe. They use respiration when oxygen is present and fermentation when it is not. Represents the majority of pathogens

36
Q

What is the name for bacteria that grow well at low oxygen concentrations?

A

microaerophilic

37
Q

What is the Lancefield antigen?

A

a carbohydrate from Streptococcus that is used to distinguish pathogenic members of the group.

38
Q

In serotyping, what does H-antigen refer to?

A

Flagella

39
Q

What does O-antigen refer to in serotyping?

A

LPS (lipopolysaccharide)

40
Q

What is RFLP?

A

Restriction Fragment length polymorphism. It is a technique of mapping DNA fragments of varying sizes.

41
Q

What is RFLP?

A

Restriction Fragment length polymorphism. It is a technique of mapping DNA fragments of varying sizes.

KN-Micro Block 1 (7 decks)

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