Bacteriophage Flashcards
what is a bacteriophage
viruses that infect bacteria
what does a phage particle generally consist of
a genome (ssDNA or dsDNA) contained within a protein capsid
what is a virus
a noncellular particle that infects a host cell and directs it to produce progeny particles
why does the replication of phage require host cell machinery
energy production and nutrient aquisition, particle building blocks (nucleotides and amino acids), protein synthesis
what is the lytic phage replication cycle
- bacteriophage attaches to host cell 2. phage inserts its DNA (genome) 3. phage genome circularizes 4. cell synthesizes capsid proteins 5. host DNA is degraded and cell replicates phage genome 6. phage DNA is packaged into capsids 7. host cell is lysed to release phage progeny
how do bacteriophage perform step one of the lytic cycle (attach to the bacterium) / is this attachment specific / how does specificity possibly differ
the tail fibers on the phage have tips that contain proteins that bind to important bacterial surface molecules / yes this attachment is specific / could be species specific or strain within a species specific
what is a capsular polysaccharide / how do phage get around it
it defends the cell against phage infection as a physical barrier / they have enzymes on the tip of their tail fiber that chews through the polysaccharide and binds to the LPS
how does the viral DNA enter the bacterium / what does the tail fiber do for insertion of DNA
when the phage attaches it triggers a structural rearrangement of phage tail sheath (contracts) / it penetrates the host cell envelope that releases the phage genome
what drives the translocation of the DNA into the host cell
the pressure within the capsid
what are the early genes expressed in phage reproduction
DNAse and DNA replication machinery
what does the early DNAse do
degrades the host genomic DNA which opens up important nucleotides
when is the DNA replication machinery produced
when the DNA is circularized
what are the late genes produced in replication and particle assembly of phage
capsid proteins, DNA packaging machine, holins and lysins
what do the capsid proteins do / what does the DNA packaging machine do
they self-assemble to form empty particles / loads the phage particle with replicated genome (uses ATP)
how do bacterial cells detect the phage DNA from their own
they methylate their DNA so nucleases know what to selectively degrade