Brainscape's Knowledge GenomeTM


Top Flashcards (Certified)
All Flashcards

Microbiology/Lab Medicine > Bacterial Structure and Classification > Flashcards

Bacterial Structure and Classification Flashcards

(71 cards)

Start Studying
1
Q

Classification of bacteria is largely determined by what?

A

structure

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

pathogenic properties of bacteria can be dependent on specific structure such as ___

A

pili and capsules

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

the structures unique to bacteria are also the bases and targets of ____

A

antimicrobial therapy

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

what are the 2 major shapes of bacteria?

A

rods (bacilli) and spheres (cocci)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

chains of cocci =

A

streptococci

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

cocci in pairs =

A

diplococci

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

cocci in grape-like clusters =

A

staphylococci

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

which type of cocci is most infectious?

A

staphylococci

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

comma-shaped bacteria =

A

vibrio

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

corkscrew shape bacteria =

A

spirilli and spirochetes

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

the bacterial genome usually comprises what?

A

single, circular DNA chromosome that lacks introns and is not bound by histone proteins

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

do bacteria have cell walls?

A

yes

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

what are bacterial cell walls composed of?

A

peptidoglycan

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

the cell wall provides ___ for the bacteria and also serves as ___ for antimicrobial therapy

A

provides rigidity; major target

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

how do the cell walls of gram positive and gram negative bacteria differ?

A

gram positive: very thick, heavily cross-linked, lies external to cytoplasmic membrane, contains teichoic and lipoteichoic acid (up to 50%)
gram negative: thin, lightly cross-linked, lies bw inner cytoplasmic and outer membrane in periplasmic space

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

the bacterial lipid membrane lacks what?

A

sterols

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

what is special about the membrane of gram negative bacteria?

A

they have 2 lipid membranes

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

what is the role of pili (fimbrae)?

A

1) attach bacteria to host cell surfaces (major)

2) ‘sex pilus’ used to transmit genetic material from one bacterium to another during conjugation

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

what is the role of flagella?

A

allow motile bacteria to swim

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
20
Q

flagella bear what antigen which is used in serotyping?

A

H

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
21
Q

do all bacteria have pili? flagella?

A

no; no

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
22
Q

what are capsules?

A

external structures composed of either polysaccharide or polypeptides

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
23
Q

what is the role of capsules?

A

protect encapsulated bacteria from phagocytosis

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
24
Q

not all bacteria are encapsulated, but nearly all bacterium causing ___ contains a capsule

A

meningitis

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
25
how can capsules be visualized?
by their ability to exclude dyes from immediate proximity of bacterium
26
what are spores?
dehydrated, dormant forms of bacteria that allow them to survive during harsh conditions
27
can both gram negative and gram positive bacteria form spores?
only gram positive rods
28
the cytoplasmic membrane of gram pos/neg bacteria contains many ___ necessary to bring in nutrients.
transport proteins
29
the outer membrane of gram negative bacteria serves as an additional ___
permeability barrier
30
is the outer membrane of gram negative bacteria charged? why or why not?
yes, negatively charged which helps bacteria evade phagocytosis, hinder antibiotic uptake, and avoid action of complement
31
the outer membrane of gram negative bacteria contains ___ to allow import of nutrients
porins
32
the periplasm is home to ___ some of which destroy antibiotics
degradative enzymes
33
unique to the outer membrane of gram neg. bacteria is ___, found in the outer leaflet of the membrane.
lipopolysaccharide (LPS)
34
what does LPS contain?
``` lipid A (toxic phospholipid, aka endotoxin) core polysaccharide O antigen polysaccharide (major surface antigen of gram neg. bacteria) ```
35
lipid A is recognized by the ___ which elicits what response?
innate immune system --> cytokine storm leading to septic shock
36
the successful pathogenesis by some bacteria depends on their ability to ___
secrete proteins or other substances from the cell
37
describe the Type I protein secretion system
- members of ABC transporter family - encoded by all gram neg bacteria - proteins are directly secreted into EC environment from cytoplasm
38
what is the significance of the type I secretion system with regards to bacterial pathogenesis?
antimicrobial drugs can be expelled from the cell using these systems, thus promoting resistance to the antibiotic
39
describe the Type II protein secretion system
- found in all gram negative bacteria - serve as the general secretory pathway, used to deliver proteins to periplasm and EC spaces - proteins first secreted to the periplasm before being secreted across outer membrane
40
describe the Type III protein secretion system
- found only in pathogens - hydrophobic segments of the Type III system span cytoplasmic and outer membranes of gram negative cell as well as plasma membrane of animal cell
41
why are type III secretion systems referred to as molecular syringes?
bc their structure allows direct injection of toxins and other virulence factors into cytosol of a targeted animal cell
42
what are the bases for gram staining?
differing peptidoglycan depths and extent of cross-linking
43
in gram staining, the extensive cell wall of Gram ___ bacteria retains the crystal violet while the thin layer of peptidoglycan found in Gram ___ bacteria does not.
positive; negative
44
peptidoglycan is a major target for ___
antimicrobial therapy
45
Peptidoglycan is composed of a backbone of repeating disaccharides comprising ___
N-acetylmuramic acid (NAM) and N-acetylglucosamine (NAG)
46
what enzyme links the disaccharides in peptidoglycan to form long chains?
transglycosylase
47
what is attached to the NAM residue of | each disaccharide?
pentapeptide composed of L- and D-isomers of amino acids;
48
what enzymes are involved in cross-linking?
transpeptidases (penicillin-binding proteins) and carboxypeptidases
49
how does the cross-linking differ bw gram | positive and gram negative bacteria?
simple bond in Gram negative bacteria, but in Gram positive bacteria, a pentaglycine interpeptide links the polypeptides
50
NAM-pentapeptides contain a terminal D-alanine pair which is critical for what?
crosslinking process making them a target for antimicrobials
51
cell wall assembly begins where?
cytoplasm
52
what are the steps of cell wall assembly that occur in the cytoplasm?
individual NAM-NAG disaccharides linked to a pentapeptide side chain are synthesized and attached via a diphosphate linkage to a lipid carrier
53
how do the cytoplasmic cell wall components make it out of the cytoplasm?
the lipid carrier is localized in the cytoplasmic membrane and is used to transport individual disaccharide pentapeptide subunits across the membrane to the external face of the cytoplasmic membrane
54
once external to the cytoplasmic membrane, what happens to the cell wall components?
subunit is incorporated into the growing cell wall by the action of glycosidases and transpeptidases
55
once external to the cytoplasmic membrane, what happens to the lipid carrier? why is this significant?
lipid carrier recycles to the interior leaflet of the cytoplasmic membrane to recharge with new cargo, but only after dephosphorylation --> dephos. is antimicrobial target
56
what is lysozyme?
a glycosidase that hydrolyzes the bond bw NAM and NAG, which disrupts the sugar backbone (instead of the pentapeptide cross-links)
57
where can lysozyme be found?
tears, saliva, in lysosomes of phagocytic cells
58
what was the first beta-lactam that was discovered?
penicillin
59
what is a beta-lactam? why is it important?
drugs containing a beta-lactam ring, which structurally resembles the D-alanine D-alanine terminal pair of the pentapeptide side chains; bc of this resemblance, the beta-lactams are bound by the transpeptidases (i.e., penicillin-binding proteins) of the bacteria and prevent cross-linking from occurring
60
how does the mechanism of action of the glycopeptide vancomycin differ from beta-lactams?
directly binds the D-alanine D-alanine pair while the cell wall subunit is still attached to its lipid carrier, blocking its availability for subsequent incorporation into the growing cell wall.
61
what is problem with beta-lactams and glycopeptides?
resistance
62
how do bacteria resist beta-lactams?
the beta-lactam ring is cleaved by beta-lactamases produced in resistant bacteria; other resistant bacteria produce mutated transpeptidases that no longer bind beta-lactams
63
how do bacteria resist glycopeptides like vancomycin?
D-alanine D-lactone is synthesized by bacteria instead of D-alanine D-alanine. The new pair is still recognized by transpeptidases, but not vancomycin
64
beta-lactams require what for activity?
cell growth
65
when beta-lactams inhibit the cross-linking of new subunits, cells ___ due to a loss of structural integrity
lyse
66
what is the growth property of bacteria most associated with classification?
response to oxygen
67
aerobic bacteria =
require oxygen and use respiration for growth
68
anaerobic bacteria =
inhibited or killed in the presence of oxygen and use fermentation exclusively for metabolism
69
facultative bacteria =
represent the majority of pathogens and use respiration in the presence of oxygen and use fermentation in its absence
70
microaerophilic baceria =
grow in the absence of oxygen, but grow optimally at low oxygen concentrations (5-10%)
71
the basis of classification of bacteria includes:
```  Morphology  Arrangement  Staining properties  Growth properties  Fermentation properties  Other enzymatic and virulence properties  Antigenicity  Genotype ```

Microbiology/Lab Medicine (3 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2025 Bold Learning Solutions. Terms and Conditions