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53 Cards in this Set

  • Front
  • Back
How do plasmids replicate?
independently of the bacterial chromosome
What enzyme do transposable elements encode for?
transposase (tnp)
What is transposease?
recomb enzyme that recognizes ITR and nicks DNA to be transfered to another location
With what 2 methods does transposition occur?
1. replicative
2. cut and paste
What is instertion sequence transposons?
tnp flanked by inverted repeats
What are composite transposons?
central region of Ab resistance or toxin flanked by 2 insertion sequences
What is the TnA family transposons?
a tnpA gene with 2 inverted repeats, a repression site, and b-lactimase gene
What is the bacteriophage transposon?
gene for head and tail
and inverted repeat seg
what does phase variation in e. coli fimbriae cause?
site specific inversion seq that turns on or off sticky things that cause bactiria to clump and adhere to epithelia surface
What is a major difference between pathogenicity island and normal DNA
G/C content
What is often found in pathogenticity islands?
flanked by short direct sequ repeats indicative of transfer via bacteriaphage
What does natural transformation entail?
unptake of DNA from envior by competent cells in Gm + and -
What happens to the DNA before it is taken up in natural transformation?
it is processed from ds to ss
What are 2 fates of the DNA taken up in natural transformation?
1. degradation
2. homologus recomb
What happens in conjugation?
DNA is passed uni-directionally via a bridge or cell to cell contact
What is transfered in cojugation?
pathogenicity islands
What does the donor cell keep in conjugation?
a copy of the original DNA
What is the specific site recognized for transfer in cojugation called?
How do Gram - cells go through conjugation?
donor produces pilus hollow fil (bridge)and interacts with receptor on host
How do Gram + cells go through conjugation?
recipient secretes phermones to promote aggregation to intitate cell to cell contact
What type of ssDNA replication occurs in conjugation?
rolling circle replication
What type of cells are bacteriophages?
obligate intracellular parasites
what are the 3 main types of bacteriaphages?
1. icosahedral head w/ no tail
2. icosahedral head w/ tail
3. filamentous
What are the possible life cycles for a bacteriophage?
integrate into host choromosome
capable of both lytic and lysogenic
What can be transfered via transduction?
genomic DNA
What type of DNA is transfered in transduction?
double stranded
What limits transduction?
host range (cell receptors)
What is the mechanism of transduction?
phage binds host receptor
viral dna injected
viral dna replicated, capsid made, host dna fragmented
viral dna packaged and released
What is cholera toxin carried on?
CTXphage -> filamentous bacteriophage
What are the toxin genes in cholera?
CTX 5B to 1A
(5 binding 1 enzyme)
Waht is Ace and Zot?
in cholera toxin resposible for phage morphogenesis and enterotixic activity
What type of bacteriophage is cholera/
what type of cholera results in worse symptoms?
genome associated
Where is tcp encoded in cholera?
pathogenicity island
tcp = phage receptor
What induces transfer of cholera?
UV light
Disease causing strains of cholera include:
classical O1 - 2 copies
El Tor O1
O139 > 1 tandem arrangement
What is shiga toxin encoded by?
STX phage
What type of phage is shiga toxin?
isohedral head with tail
What type of DNA does shiga toxin have?
double stranded
What is the life cycle of the shiga toxin phage?
what is phage morphogenesis linked with?
host cell lysis
stx experssing STX phage is found in?
shigella dysenteriae
E.coli (STEC)
How homologus are STX1 and STX2?
What is found in shigella dysentariae 1?
STX1 is a defective prophage in shigella dysenteriae...
it cannot be excised form the host chromosome following induction
STX1 can still express stx but cannot
be transmitted to new hosts (phage head and tail genes are deleted)
S. dysenteriae 1 carrying STX1 is the most common cause of HUS in
developing countries
what is the most common serotype associated with stx production STX2
E.coli O157:H7
STEC is the most common cause of HUS
in the United States
stx is located
in region with phage maturation genes