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Flashcards in Bacterial Structure and Classification Deck (71)
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1

Classification of bacteria is largely determined by what?

structure

2

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

pili and capsules

3

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

antimicrobial therapy

4

what are the 2 major shapes of bacteria?

rods (bacilli) and spheres (cocci)

5

chains of cocci =

streptococci

6

cocci in pairs =

diplococci

7

cocci in grape-like clusters =

staphylococci

8

which type of cocci is most infectious?

staphylococci

9

comma-shaped bacteria =

vibrio

10

corkscrew shape bacteria =

spirilli and spirochetes

11

the bacterial genome usually comprises what?

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

12

do bacteria have cell walls?

yes

13

what are bacterial cell walls composed of?

peptidoglycan

14

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

provides rigidity; major target

15

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

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

16

the bacterial lipid membrane lacks what?

sterols

17

what is special about the membrane of gram negative bacteria?

they have 2 lipid membranes

18

what is the role of pili (fimbrae)?

1) attach bacteria to host cell surfaces (major)
2) 'sex pilus' used to transmit genetic material from one bacterium to another during conjugation

19

what is the role of flagella?

allow motile bacteria to swim

20

flagella bear what antigen which is used in serotyping?

H

21

do all bacteria have pili? flagella?

no; no

22

what are capsules?

external structures composed of either polysaccharide or polypeptides

23

what is the role of capsules?

protect encapsulated bacteria from phagocytosis

24

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

meningitis

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