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53 Cards in this Set
- Front
- Back
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How do plasmids replicate?
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independently of the bacterial chromosome
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What enzyme do transposable elements encode for?
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transposase (tnp)
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What is transposease?
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recomb enzyme that recognizes ITR and nicks DNA to be transfered to another location
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With what 2 methods does transposition occur?
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1. replicative
2. cut and paste |
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What is instertion sequence transposons?
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tnp flanked by inverted repeats
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What are composite transposons?
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central region of Ab resistance or toxin flanked by 2 insertion sequences
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What is the TnA family transposons?
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a tnpA gene with 2 inverted repeats, a repression site, and b-lactimase gene
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What is the bacteriophage transposon?
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gene for head and tail
and inverted repeat seg |
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what does phase variation in e. coli fimbriae cause?
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UTIs
site specific inversion seq that turns on or off sticky things that cause bactiria to clump and adhere to epithelia surface |
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What is a major difference between pathogenicity island and normal DNA
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G/C content
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What is often found in pathogenticity islands?
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flanked by short direct sequ repeats indicative of transfer via bacteriaphage
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What does natural transformation entail?
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unptake of DNA from envior by competent cells in Gm + and -
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What happens to the DNA before it is taken up in natural transformation?
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it is processed from ds to ss
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What are 2 fates of the DNA taken up in natural transformation?
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1. degradation
2. homologus recomb |
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What happens in conjugation?
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DNA is passed uni-directionally via a bridge or cell to cell contact
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What is transfered in cojugation?
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plasmids
transposon pathogenicity islands |
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What does the donor cell keep in conjugation?
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a copy of the original DNA
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What is the specific site recognized for transfer in cojugation called?
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OriT
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How do Gram - cells go through conjugation?
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donor produces pilus hollow fil (bridge)and interacts with receptor on host
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How do Gram + cells go through conjugation?
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recipient secretes phermones to promote aggregation to intitate cell to cell contact
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What type of ssDNA replication occurs in conjugation?
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rolling circle replication
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What type of cells are bacteriophages?
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obligate intracellular parasites
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what are the 3 main types of bacteriaphages?
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1. icosahedral head w/ no tail
2. icosahedral head w/ tail 3. filamentous |
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What are the possible life cycles for a bacteriophage?
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lytic
lysogenic temperate |
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Lysogenic
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integrate into host choromosome
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lytic
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replicative
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Temperate
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capable of both lytic and lysogenic
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What can be transfered via transduction?
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plasmids
transposons genomic DNA |
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What type of DNA is transfered in transduction?
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double stranded
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What limits transduction?
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host range (cell receptors)
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What is the mechanism of transduction?
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phage binds host receptor
viral dna injected viral dna replicated, capsid made, host dna fragmented viral dna packaged and released |
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What is cholera toxin carried on?
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CTXphage -> filamentous bacteriophage
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What are the toxin genes in cholera?
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CTX 5B to 1A
(5 binding 1 enzyme) |
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Waht is Ace and Zot?
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in cholera toxin resposible for phage morphogenesis and enterotixic activity
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What type of bacteriophage is cholera/
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temperate
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what type of cholera results in worse symptoms?
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genome associated
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Where is tcp encoded in cholera?
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pathogenicity island
tcp = phage receptor |
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What induces transfer of cholera?
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UV light
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Disease causing strains of cholera include:
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classical O1 - 2 copies
El Tor O1 O139 > 1 tandem arrangement |
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What is shiga toxin encoded by?
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STX phage
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What type of phage is shiga toxin?
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isohedral head with tail
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What type of DNA does shiga toxin have?
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double stranded
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What is the life cycle of the shiga toxin phage?
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temperate
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what is phage morphogenesis linked with?
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host cell lysis
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stx experssing STX phage is found in?
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shigella dysenteriae
E.coli (STEC) |
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How homologus are STX1 and STX2?
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55%
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What is found in shigella dysentariae 1?
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STX1
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STX1 is a defective prophage in shigella dysenteriae...
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it cannot be excised form the host chromosome following induction
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STX1 can still express stx but cannot
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be transmitted to new hosts (phage head and tail genes are deleted)
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S. dysenteriae 1 carrying STX1 is the most common cause of HUS in
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developing countries
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what is the most common serotype associated with stx production STX2
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E.coli O157:H7
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STEC is the most common cause of HUS
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in the United States
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stx is located
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in region with phage maturation genes
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