Bacterial Genetic Variation, Gene Transfer, and Evolution of Virulence Flashcards
Name 3 general ways bacteria regulate gene expression in order to adapt to the environment.
- regulate transcription 2. DNA rearrangement 3. acquisition of new DNA segments
How are bacterial plasmids transferred among gram positive bacteria?
generalized transduction
What is spontaneous mutation?
random single base changes
What are complex transposons?
those that carry add’l genes, such as antibiotic resistance, toxins, adhesions, and other virulence factors
____ is naked DNA transfer, usually btw members of the same species.
transformation
Proteins that mediate transposition are called a ____.
transposase
What is the simplest method of phage-mediated gene transfer?
generalized transduction
_____ may encode antibiotic resistance, especially resistance to tetracycline.
Conjugative transposons
What is bacterial conjugation?
genetic transfer req contact btw donor and recipient; usu. involves a plasmid
What is phase variation?
DNA rearrangement
What is a large segment of DNA carried by some, but not all, bacteria that contribute to virulence called?
a pathogenicity island
What is a transposon?
a segment of DNA that can move itself from one chromosome to another
How are new DNA segments acquired?
lateral transfer
A segment of DNA that can move itself from one chromosome to another is called a ____.
transposon
Conjugative plasmids, such as transmissible drug resistance plasmids, are _____.
self-transmissible
Name 2 spontaneous mutations that are of medical importance.
- increased resistance to antimicrobials in Pseudomonas and Mycobacterium 2. single aa change in pyogenic exotoxin B of Strep. pyogenes converts it to a more invasive disease
____ is when bacteria integrate viral genes into their own genome and express viral virulence genes.
Bacteriophage conversion
What is a pathogenicity island?
large segments of DNA carried by some, but not all, bacteria that contribute to virulence
Generalized transducing phages are formed as a consequence of _____ during phage assembly.
errors in DNA packaging
What is a transductant?
the genetic recombinant
Plasmids may acquire new genetic material, especially by _____.
transposition
What is an insertion sequence/IS element?
transposons that encode transposase
What is transformation?
naked DNA transfer, usually btw members of the same species
What is transduction?
gene transfer mediated by bacteriophages
What is recombination?
gene swapping/rearrangement within a single organism or btw similar organisms
Transposons that encode transposase are called ____ or ____.
insertion sequences; IS elements
What do Neisseria gonorrhoeae do via phase variation?
alternate cell surface pilli
Bacterial isolates that lack PIs may be _____ or have a different disease-causing potential.
avirulent
___ plasmids, such as transmissible drug resistance plasmids, are self-transmissible.
Conjugative
Acquisition of new genes may alter the ____, ____, or _____ of the new organism.
alter the virulence potential, survival characteristics, antimicrobial resistance
What is a circular, self-replicating, extrachromosomal piece of DNA called?
a plasmid
Conjugative transposons may encode antibiotic resistance, especially resistance to _____.
tetracycline
____ carry add’l genes, such as antibiotic resistance, toxins, adhesions, and other virulence factors.
Complex transposons
What is generalized transduction?
any segment of the donor cell genome may be passed to another cell
Describe the Plasmid F.
found in lab strain E. coli; self-transmissible; 2% of chromosome; codes for autonomous replication, sex pilli, conjugative transfer, integration
How does Neisseria gonorrhoeae use recombination?
to produce new pilli genes
How are plasmids transferred?
conjugation or transduction
What is the oriT?
origin of transfer- where circular DNA is opened to begin the conjugation process
Gene swapping/rearrangement within a single organism or btw similar organisms is called _____.
recombination
What is a plasmid?
a circular, self-replicating, extrachromosomal piece of DNA
Name the stages of bacteriophage reproduction.
- growth 2. temperate phase 3. transduction 4. bacteriophage conversion
Virulence genes are often only expressed under conditions of _____ within the host.
low iron
How are plasmids that cannot mediate their own transfer be mobilized?
by another plasmid in the same cell
What do Salmonella typhimurium do via phase variation?
switch btw H1 and H2 flagellar antigens
What is another name for bacteriophage conversion?
lysogenic conversion
Give an example of bacteriophage conversion.
C. diptheriae toxin, cholera toxin, scarlet fever toxin, botulism toxin
What is the rate of spontaneous mutation in a bacteria?
very low- 10^-6 to -10 per cell-generation
_____ is gene transfer mediated by bacteriophages.
transduction
What is bacteriophage conversion?
when bacteria integrate viral genes into their own genome and express viral virulence genes
What does injected DNA recombine with in order to produce a genetic recombinant?
homologous genome segments
What are conjugative transposons?
mobile elements that mediate the conjugation btw 2 cells- the DNA is the conjugative transposon itself
What is bacteriophage conversion?
when viral gene products are produced by bacteria that don’t have those genes otherwise
What can plasmids carry?
virulence and antibiotic resistance genes
What is transposase?
proteins that mediate transposition
How do bacteria increase or decrease gene transcription?
via DNA-binding proteins that interact with the promoter regions
