GENE TRANSFER IN BACTERIA
A change in the genome of a bacterium may be due either to mutation in the organism's own DNA or to acquisition of DNA from an external Bacterial DNA may be transferred bacteria by three mechanisms.
1. In some species free DNA, either extracted artificially released by lysis from the cells of one strain, may be taken up directly by the r strain. Alteration of a cell's genome by DNA acquired in this manner is ailed transformation.
2. Bacterial genes may occasionally be transferred between bacteria by means of bacteriophage; this process is known as transduction. There are two types: Restricted transduction and Generalized Transduction.
3. DNA may pass between cells during conjugation, when there is direct contact with formation of a bridge between the cells.