Bacterial Virulence Factors and Bacterial Genetics Flashcards
name 3 bacterial virulence factors
- protein A
- IgA protease
- M protein
- they promote evasion of host immune response
protein A–mechanism, which bacteria?
- virulence factor
- mechanism:
- binds Fc region of IgG
- prevents opsonization and phagocytosis
- expressed by S. aureus
IgA protease–mechanism, which bacteria?
- virulence factor
- mechanism:
- enzyme that cleaves IgA
- secreted by:
- S. pneumoniae
- H. influenzae type B
-
Neisseria
- ”SHiN”
- colonize respiratory mucosa
M protein–mechanism, which bacteria?
- virulence factor
- mechanism
- helps prevent phagocytosis
- expressed by:
- group A streptococci
- shares similar epitopes to human cellular problems (molecular mimicry)
what may underlie the autoimmune response seen in acute rheumatic fever?
M protein
type III secretion system
- 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:
explain transformation as it pertains to bacterial genetics
- 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
which bacteria is transformation primarily a feature of?
- S. pneumoniae
- H. influenzae type B
-
Neisseria
- (SHiN)
conjugation: F+ x F-
- 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
conjugation: Hfr x F-
- 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
explain transposition as it pertains to bacterial genetics
- 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
explain generalized transduction
- 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
explain specialized transduction
- 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
genes for which 5 bacterial toxins are encoded in a lysogenic phage:
-
ABCD’S
- Group A strep erythrogenic toxin
- Botulinum toxin
- Cholera toxin
- Diphtheria toxin
- Shiga toxin
explain spore forming bacteria
- 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
name the spore forming bacteria
- Bacillus anthracis
- Bacillus cereus
- Clostridium botulinum
- Clostridium difficile
- Clostridium perfringens
- Clostridium tetani
what results from Bacillus anthracis?
anthrax
what results from Bacillus cereus?
food poisoning
what results from Clostridium botulinum?
botulism
what results from Clostridium difficile?
Pseudomembranous colitis
what results from Clostridium perfringens?
gas gangrene
what results from Costridium tetani?
tetanus