Flashcards in Bacterial Structure and Classification Deck (71)
Classification of bacteria is largely determined by what?
pathogenic properties of bacteria can be dependent on specific structure such as ___
pili and capsules
the structures unique to bacteria are also the bases and targets of ____
what are the 2 major shapes of bacteria?
rods (bacilli) and spheres (cocci)
chains of cocci =
cocci in pairs =
cocci in grape-like clusters =
which type of cocci is most infectious?
comma-shaped bacteria =
corkscrew shape bacteria =
spirilli and spirochetes
the bacterial genome usually comprises what?
single, circular DNA chromosome that lacks introns and is not bound by histone proteins
do bacteria have cell walls?
what are bacterial cell walls composed of?
the cell wall provides ___ for the bacteria and also serves as ___ for antimicrobial therapy
provides rigidity; major target
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
the bacterial lipid membrane lacks what?
what is special about the membrane of gram negative bacteria?
they have 2 lipid membranes
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
what is the role of flagella?
allow motile bacteria to swim
flagella bear what antigen which is used in serotyping?
do all bacteria have pili? flagella?
what are capsules?
external structures composed of either polysaccharide or polypeptides
what is the role of capsules?
protect encapsulated bacteria from phagocytosis
not all bacteria are encapsulated, but nearly all bacterium causing ___ contains a capsule
how can capsules be visualized?
by their ability to exclude dyes from immediate proximity of bacterium
what are spores?
dehydrated, dormant forms of bacteria that allow them to survive during harsh conditions
can both gram negative and gram positive bacteria form spores?
only gram positive rods
the cytoplasmic membrane of gram pos/neg bacteria contains many ___ necessary to bring in nutrients.
the outer membrane of gram negative bacteria serves as an additional ___