bacterial structure and function

Question 1

external bacterial structures

Answer 1

• flagella
• capsules
• pili

Question 2

capsule structure

Answer 2

• organic polymers (usually polysaccharides) that form hydrophilic gels surrounding some bacteria
• 95% water

*bacillus anthracis has a peptide capsule

Question 3

capsule function

Answer 3

• prevent desiccation in environment

- increase virulence: prevent engulfment by phagocytes and complement activation

Question 4

pathogens where capsule is an important virulence determinant

Answer 4

• strep pneumoniae
• neisseria meningitidis
• haemophilus influenzae

also:

• klebs
• group B strep
• some E. coli
• bacillus anthracis

Question 5

clinical consequence of infection with bacteria with capsule

Answer 5

• bacteremia in individuals w/o a functional spleen

- meningitis

Question 6

K, H, and O antigens

Answer 6

K = capsule
H = flagella
O = O antigen

Question 7

flagella structure

Answer 7

• long, helical filaments (0, 1, 2, or many per cell)
• filament is made via self assembly of flagellin monomers and connected to a hook + basal body in envelope
• basal body = motor

Question 8

flagella function

Answer 8

• mobility
• allow for chemotaxis: ability to move toward attractants and away from repellants
• “running” = counterclockwise flagella rotation
• “tumbling” = clockwise rotation
• bind TLR-5 and NLRC4 => inflammatory response

Question 9

fimbrae/pili structure

Answer 9

• long filamentous structures distributed over the cell surface
• made mainly of pilin subunits but may have other proteins too

Question 10

pili function

Answer 10

• allow for adherence to cells/tissues of the host and biofilm formation
• bind receptors (sugars on glycolipids or glycoproteins) in the host cell membrane
• bind specifically: different pili bind receptors on different kinds of tissues

Question 11

variation of surface antigens

Answer 11

phase variation:
- ability to turn flagellin/pilin production on/offf

antigenic variation:
- change type of pilin produced to avoid detection by host (neisseria)

Question 12

bacterial ribosomal subunits (vs eukaryotes)

Answer 12

bacterial 70S ribosome = 50S + 30S subunits

• 50S = 23S RNA + 5S RNA + proteins
• 30 S = 16S RNA + proteins

eukaryotic 80S ribosome = 60S + 40S subunits

Question 13

bacterial DNA replication

Answer 13

• replication by DNA polymerase
• replication begins at oriC
• circular daughter chromosomes will be linked => DNA gyrase (topoisomerases) deconcatenate

Question 14

operons

Answer 14

clusters of genes may be transcribed from a single promoter into a single mRNA

(not in eukaryotes)

Question 15

eukaryotic vs prokaryotic translation

Answer 15

occurs co-transcriptionally

Question 16

spore formation

Answer 16

• develop within a vegetative (dividing) cell under adverse conditions
• released when the bug dies

Question 17

spore function

Answer 17

• very resistant to environmental stresses (heat, UV, drying, chemicals)
• unfavorable conditions = dormant => favorable conditions => germination

Question 18

bacteria that form spores

Answer 18

• clostridium

- bacillus