Bacterial Virulence Factors and Bacterial Genetics Flashcards
1
Q
name 3 bacterial virulence factors
A
- protein A
- IgA protease
- M protein
- they promote evasion of host immune response
2
Q
protein A–mechanism, which bacteria?
A
- virulence factor
- mechanism:
- binds Fc region of IgG
- prevents opsonization and phagocytosis
- expressed by S. aureus
3
Q
IgA protease–mechanism, which bacteria?
A
- virulence factor
- mechanism:
- enzyme that cleaves IgA
- secreted by:
- S. pneumoniae
- H. influenzae type B
-
Neisseria
- ”SHiN”
- colonize respiratory mucosa
4
Q
M protein–mechanism, which bacteria?
A
- virulence factor
- mechanism
- helps prevent phagocytosis
- expressed by:
- group A streptococci
- shares similar epitopes to human cellular problems (molecular mimicry)
5
Q
what may underlie the autoimmune response seen in acute rheumatic fever?
A
M protein
6
Q
type III secretion system
A
- also known as “injectisome”
- needle like protein appendage facilitating direct delivery of toxins from certain gram - bacteria to a eukaryotic host cell
- gram - bacteria include:
- Pseudomonas
- Salmonella
- Shigella
- E. coli
- gram - bacteria include:
7
Q
explain transformation as it pertains to bacterial genetics
A
- ability to take up naked DNA (ie. from cell lysis) from environment (also known as “competence”)
- a feature of many bacteria
- any DNA can be used
- adding deoxyribonuclease to environment will degrade naked DNA in medium –> no transformation seen
8
Q
which bacteria is transformation primarily a feature of?
A
- S. pneumoniae
- H. influenzae type B
-
Neisseria
- (SHiN)
9
Q
conjugation: F+ x F-
A
- F+ plasmid contains genes required for sex pilus and conjugation
- bacteria without this plasmid are termed F-
- sex pilus on F+ bacterium contacts F- bacterium
- a single strand of plasmid DNA is transferred across the conjugal bridge (“mating bridge”)
- no transfer of chromosomal DNA
10
Q
conjugation: Hfr x F-
A
- F+ plasmid can become incorporated into bacterial chromosomal DNA, termed high frequency recombination (Hfr) cell
- replication of incorporated plasmid DNA may include some flanking chromosomal DNA
- transfer of plasmid and chromosomal genes
11
Q
explain transposition as it pertains to bacterial genetics
A
- segent of DNA (ie. transposon) that can “jump” (excision and reintegration) from one location to another, can transfer genes from plasmid to chromosome and vice versa
- when excision occurs, may include some flanking chromosomal DNA, which can be incorporated into a plasmid and transferred to another bacterium
- ie. vanA gene from vancomycin resistant Enterococcus to S. aureus
- when excision occurs, may include some flanking chromosomal DNA, which can be incorporated into a plasmid and transferred to another bacterium
12
Q
explain generalized transduction
A
- a “packaging” event
- lytic phage infects bacteria–leads to cleavage of bacterial DNA
- parts of bacterial chromosomal DNA may become packaged in phage capsid
- phage infects another bacterium which transfers the genes
13
Q
explain specialized transduction
A
- an “excision” event
- lysogenic phage infects bacterium and viral DNA incorporates into bacterial chromosome
- when phage DNA is excised, flanking bacterial genes may be excised with it
- DNA is packaged into phage capsid and can infect another bacterium
14
Q
genes for which 5 bacterial toxins are encoded in a lysogenic phage:
A
-
ABCD’S
- Group A strep erythrogenic toxin
- Botulinum toxin
- Cholera toxin
- Diphtheria toxin
- Shiga toxin
15
Q
explain spore forming bacteria
A
- some bacteria can form spores at the end of the stationary phase when nutrients are limited
- spores are highly resistant to heat and chemicals
- have dipicolinic acid in their core
- have no metabolic activity
- must autoclave to potentially kill spores (as is done to surgical equipment) by steaming at 121 deg C for 15 min
