Heat shock response: caused by a cell stress regulon that responds to heat and chemical stress. One response to heat shock is synchronization of cell division.
Cell Survival
Survival Regulons: include theSOS system, Heat-shock response (
Ý certain proteases and protein chaperones), Osmotic shock regulons
Sporulation: =production of endospores in a few Gram + rod species (involves sequential activation of interrelated regulon)
rods only; protects from drying, heat, UV, and chemicals
important spore former diseases; anthrax, gas gangrene, tetanus and botulism
survival structure; formation results from walling off of nucleoid and cytosol by invagination of cell membrane (becomes spore membrane) then addition of cortex,coat,exosporium. Protects from
Ý pH, desiccation, toxic environment.
Staining: fix with malachite green, steam, counter stain with pink saffronine = visible green spores, pink cellular material
Bacteriophages (aka Phages)
phages are viruses that infect bacteria
viruses hi-jack DNA replication apparatus to multiply their own genome
consist minimally of proteins and nucleic acids
categorized by genomic n.a. structure: Single strand vs double stranded; RNA vs DNA (i.e.2X strand DNA: lambda)
genomes vary greatly in size and can have over lapping reading frames. Encodes for phages specific proteins (i.e. capsid)
can not generate ATP, completely dependent on host for metabolic pools and enzymes
capsid = surface proteins (some use host membranes as a cover).
Lytic Cycle of Vegetative Growth
Infection
of cell by binding surface structure receptor that is specific to the bacterial species targeted by virus; includes insertion of DNA into host (utilizing the electrochemical gradient across cell membrane)
Expression
of viral genome by means of viral genes or hi-jacked host genes to produces necessary enzymes for replication etc.
Replication
of viral genome and synthesis of structural proteins (i.e. capsid)
Assembly
of new phage particles inside host. This event creates the opportunity for recombination of host DNA with viral DNA.
Lytic Phage
: will replicate and assemble until cell burst, destroying cell and is visualized as a clear plaque on a plate.
Lysogenic Cycle of Temperate Phage
Infection
same as above
Prophage
is formed by recombination of phage chromosomes into host chromosome. Thus viral DNA is propagated without lysis
Cell is now called Lysogen (recombined phage DNA = prophage)
Reinfection of lysogen by other phage prevented by:
(1) altering recognition sites to prevent binding
(2) generating a binding repressor protein
Temporate phage can exist independent of host chromosome but is replicated and distributed with it.
Lysogens can be triggered to pop prophage out of host DNA and start lytic cycle by heat, UV, starvation, almost any stressor.
A Study has shown that cell count of 104 within 3-4 miles of sewage treatment plant on Chesapeake Bay. This creates enough replication events to make rare and dangerous mutations likely.
Symbiotic relationships between vertebrates and bacteria abound in GI; rumen of cow contain cellulase producing bacteria, human GI contains Vitamin producing bacteria.