Molecular genetics of bacteria. Gene regulation and regulation of metabolism Genetic exchange among bacteria. Bacteria are successful because They carefully regulate their use of energy in metabolic processes by shutting down unneeded pathways at the biochemical and genetic levels.
Bacteria must respond quickly to changes in the environment.
Bacteria are small compared to their environment, have no real capacity for energy storage.
Simultaneous transcription and translation allows them to
synthesize the proteins they need quickly.
Wasteful activities are avoided. If there are sufficient amounts
of some metabolite, bacteria will avoid making more AND avoid making the enzymes that make the metabolite.
Biochemical regulation and genetic regulation.
P O are the promoter
and operator regions.
lac Z is the gene for
lac Y is the gene for
lac A is the gene for
lac I, on a different
part of the DNA, codes
for the lac repressor,
the protein which can
bind to the operator.
Characteristic of many DNA-binding proteins
Regulation of operons:
Inducible operons: Repressor protein comes off DNARepressible operons: Repressor protein attaches to DNA
When lactose is NOT present,
the cell does not need the
enzymes. The lac repressor,
a protein coded for by the
lac I gene, binds to the DNA
at the operator, preventing
When lactose is present, and
the enzymes for using it are
needed, lactose binds to the
repressor protein, causing it
to change shape and come off
the operator, allowing RNA
polymerase to find the
promoter and transcribe.
Low basal levels of beta-galactosidase exist in the cell. This converts some lactose to the related allolactose which binds to the lac repressor protein.
Synthetic inducers such as IPTG with a similar structure can take the place of lactose/allolactose for research purposes.
Fertility plasmid: genes to make a sex pilus; replicates, and a copy is passed to another cell.
Resistance plasmid: genes that make the cell resistant to antibiotics, heavy metals.
Catabolic plasmid: example, tol plasmid with genes for breaking down and using toluene, an organic solvent.
DNA must be homologous, so transformation
only occurs between a few, close relatives.
More common, but still requires close relative.