The F factor has another capability in addition to self transfer and pilus production.
the ability to recognize chromosomal DNA sequences and through them
integrate into the chromosome.
a. Some of the sites are DNA homology and some are transposon
Mutation rate increases over spontaneous-now as high as 1 per 1000 bacterial
Transition-purine replaced by another purine, or pyrimidine with
pyrimidine b. Transversion-purine replaced by pyrimidine or vice versa
REPAIR MECHANISMS IN BACTERIA
Since there is a rate of endogenous mutation and you add chemicals to the mix, why isnt
everything mutated away? The good news is that most mutations dont survive due to
efficient repair systems in both bacteria and huma
2. Light repair occurs with UV damage. UV cyclizes two adjacent DNA bases (i.e
dimer). This forms cyclobutane dimer. In bacteria there is a visible light-activated
photolyase which splits the dimer and restores the integrity of the DNA.
Mut L activates endonuclease Mut H which cuts the new strand opposite the
methyl group (GA*TC) on the old strand. The break can come on either side of
10. MutU is a helicase which unwinds the DNA and calls in an exonuclease that
3. Regular repair would cause multiple double-strand breaks
4. So, dark repair induces SOS repair.
5. This is an error-prone system
6. Genes Umu (for UV mutagenesis) D and C are induced. They form an
aberrant DNA polymerase that adds bases to the gap with
. Bioterrorists obtain a vial of nontoxic Bacillus anthracis. They isolate, then
add DNA to this strain from a toxic isolate as well as from the closely related
Bacillus cereus, to make an exceptionally toxic variant, which has
sporulation capability. Wha
DNA TRANSFER MECHANISMS
Three mechanisms for genetic exchange have been demonstrated to operate
1. Conjugation- cell to cell contact via pilus
2. Transformation-isolated DNA taken up by cell mechanisms
3. Transduction-bacteriophage (bacterial
Classes of Plasmids
1. Transfer plasmids (including the F factor). Factor is identical to plasmid. These
plasmids code for fertility pili and can transfer freely from one cell to another
2. Resistance factor- these plasmids accumulate resistances but are
DNA IN BACTERIA
-One unique chromosome present in 2-4 copies per cell. There are bacteria with
more than one unique chromosome.
-encodes as many as 4-5000 genes. All information necessary for maintenance,
growth and division of