Bacterial Genetics
bacterial communication
endogenote: recipient cell chromosome
merodiploids: partial diploid
exogenote: incoming DNA
possible fate of exogenote
stabilized by circularization
recombination
degraded via restriction endonucleases
if plasmid has an origin, it can replicate and pass to daughter cell
site specific recombination: occurs between very different DNA molecules; usually results in integration of one into another
homologous recombination
transformation
recipient cells must be competent
homologous and heterologous DNA taken up; recombines if recipient is homologous; heterologous can persist via self replicating plasmid
only highly related DNA will successfully recombine and integrate into chromosome of recipient
How can you tell that spontaneous mutations occur?
spontaneous mutations occur a lesser frequency than induced mutation
Luria-Delbruck fluctuation experiment
replica plating
MRSA
SCCmec
bugs can become resistant upon exposure to antibiotics
disc susceptibility testing allows one to know what antibiotic an infected person may be resistant to
is a mobile genetic element
contains mecA gene which encodes for BBP2A is a penicillin binding protein which confers resistance to Pencillin
induction caused by highly mutatagenic genes lead to frameshift mutations that may confer resistance or susceptibility to a treatment
types of mutations based on biological conseqences
morphological
behavioral
auxotrophic
resistance
conditional vs lethal
Mutations based on Nucleic Acid Change
insertion/microdeletion
missense: different amino acid
inversion
nonsense: premature stop codon
duplication
Repair Mechanisms
Direct Repair
Excision Repair
Recombination Repair (backup)
repair thymine dimers
damage excised and new bases inserted
sometimes errors make it past the replication fork
bacteria methylate to identify self
restriction enzymes: two types
Type I: modification, specific binding
Type II: specific binding and cutting, useful for recombinant DNA methodology
least clinically important means of gene transfer