TRANSDUCTION

The transfer of genetic material from one cell to another by a bacteriophage is called transduction. The phenomenon of transduction was first discovered by Zinder and Lederberg while searching for sexual conjugation in Salmonella species.

The infection by a bacteriophage is accomplished in several stages such as adsorption, penetration, replication, assembly, lysis and release. In brief the virus particles first attaches to specific receptor site on bacterial call wall surface. The genetic material penetrates the bacterial call, and replicates independently by using cell machinery of the host. Consequently, the virus DNA is replicated into multiple copies, and synthesizes phage proteins. Complete phage particles are assembled and finally cell is lysed resulting in release of virus particles.

Depending on mode of reproduction that reproduction the bacteriophages are of two types, the virulent phage and the temperate phage, the phage that reproduce by using a lytic cycle are called virulent phages because they destroy the host cell such as T phage, phage lambda, etc. in contrast the temperate phages ordinarily, do not lyse the bacterial cell. The viral genome behaves as episome like F factor and becomes integrated into the bacterial chromosome. The latent form of phage genome that remains within the host without harm and integrates with chromosome is called prophage. Bacteria containing prophage are known as lysogenic bacteria and the relationship between phage and its host is called lysogeny. The lysogenic bacteria can produce phage particles under some conditions, and the phage is able to establish the phenomenon of lysogeny and behaves as temperate phage.

Usually, transduction occurs most readily between the closely related species of same genus of a bacterium i.e. intrageneric. This preference is due requirement for specific cell surface receptor for recognition of the phage. In addition, intergeneric transduction has been shown between the closely related enteric bacteria such as between E. coli salmonella or shigella species. Several genetic traits for example fermentation potential, antigens, chemical resistance are transducible.