Genetics of bacteria

Genetics of bacteria

DNA molecule of chromosome of bacteria can be altered  changes trait controlled by that gene  trait may be transmitted if bacteria does not die.
Apart from mutation, there are four other ways that the genetic make up of bacteria is altered:

1) Phage Conversion:
Occurs when bacteriophage infects a lysogenic bacteria  injects DNA into cytoplasm of bacteria

2) Transduction:
Some genetic material may be carried across from one bacterial cell to another by a bacterial virus (phage). During replication a piece of bacterial DNA is accdiently enclosed in phage particle inplace of normal phage DNA. Uncommon in nature

3) Transformation:
Recipient bacterial cell is genetically transformed by the addition of DNA fragments from another strain of bacteria – exogenous DNA is taken up from the environment  transforms the cell which then expresses the new genes. Dependant on extensive DNA homology. Very uncommon in nature. Mediated by the gene, recA.

4) Conjugation:
Two bacteria attach to each other and some genetic material is transferred from the ‘donor’ to the recipient’.

Genetic basis of resistance to antibiotics:
Resistance to antibiotics can be:
• acquired (natural insensitivity to the drug  resistance)
• intrinsic (appearance of resistance to a drug in a previously sensitive population)

Random spontaneous mutations occur continuously at a low incidence  some of these will infer resistance to an antibiotic.

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