Bacterial Virulence Factors and Bacterial Genetics

Question 1

name 3 bacterial virulence factors

Answer 1

• protein A
• IgA protease
• M protein
  
  • they promote evasion of host immune response

Question 2

protein A–mechanism, which bacteria?

Answer 2

• virulence factor
• mechanism:
  
  • binds Fc region of IgG
  • prevents opsonization and phagocytosis
• expressed by S. aureus

Question 3

IgA protease–mechanism, which bacteria?

Answer 3

• virulence factor
• mechanism:
  
  • enzyme that cleaves IgA
• secreted by:
  
  • S. pneumoniae
  • H. influenzae type B
  • Neisseria
    
    • ​”SHiN”
    • colonize respiratory mucosa

Question 4

M protein–mechanism, which bacteria?

Answer 4

• virulence factor
• mechanism
  
  • helps prevent phagocytosis
• expressed by:
  
  • group A streptococci
• shares similar epitopes to human cellular problems (molecular mimicry)

Question 5

what may underlie the autoimmune response seen in acute rheumatic fever?

Answer 5

M protein

Question 6

type III secretion system

Answer 6

• 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

Question 7

explain transformation as it pertains to bacterial genetics

Answer 7

• 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

Question 8

which bacteria is transformation primarily a feature of?

Answer 8

• S. pneumoniae
• H. influenzae type B
• Neisseria
  
  • ​ (SHiN)

Question 9

conjugation: F⁺ x F^-

Answer 9

• 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

Question 10

conjugation: Hfr x F^-

Answer 10

• 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

Question 11

explain transposition as it pertains to bacterial genetics

Answer 11

• 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

Question 12

explain generalized transduction

Answer 12

• 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

Question 13

explain specialized transduction

Answer 13

• 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

Question 14

genes for which 5 bacterial toxins are encoded in a lysogenic phage:

Answer 14

• ABCD’S
  
  • Group A strep erythrogenic toxin
  • Botulinum toxin
  • Cholera toxin
  • Diphtheria toxin
  • Shiga toxin

Question 15

explain spore forming bacteria

Answer 15

• 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

Question 16

name the spore forming bacteria

Answer 16

• Bacillus anthracis
• Bacillus cereus
• Clostridium botulinum
• Clostridium difficile
• Clostridium perfringens
• Clostridium tetani

Question 17

what results from Bacillus anthracis?

Answer 17

anthrax

Question 18

what results from Bacillus cereus?

Answer 18

food poisoning

Question 19

what results from Clostridium botulinum?

Answer 19

botulism

Question 20

what results from Clostridium difficile?

Answer 20

Pseudomembranous colitis

Question 21

what results from Clostridium perfringens?

Answer 21

gas gangrene

Question 22

what results from Costridium tetani?

Answer 22

tetanus