Horizontal gene transfer in bacteria is a process by which there is exchange of genes between bacteria but not in a traditional way like reproduction and also through bacteriophages. This is the main reason of bacteria acquiring antibiotic resistance genes.
There are three mechanism of horizontal gene transfer in bacteria which are as follows:
1. Transformation: It is defined as the process where the transfer of genetic material between bacteria is by means of extra-cellular pieces of DNA. There is direct uptake of DNA from surrounding and its incorporation into bacterial DNA or plasmid. This is common in bacterial cell which are naturally competent.
2. Conjugation: It is defined as a process where there is unidirectional transfer of genes between donor cell and recipient cell through cell-to-cell contact. At the contact a bridge or canal is formed which connects the two cells physically. Conjugation can take place between two bacterial cells or between bacterial cell and eukaryotic cell.
3. Transduction: It is defined as a process in which bacteriophages acts as an intermediates in the transfer of genes between bacterial cells. Bacteriophage infects donor cell where the bacterial genes become incorporated into few phages. When these phages infect other bacterium they transfer the genes to it.