Bacterial transduction Dr.Sujit Ghosh

Survival and advancement of microorganisms with time is fundamentally influenced by the capacity of the microorganisms to exchange hereditary material without sexual reproduction. Hereditary material can move, starting with one cell then onto the next through a few distinct mechanism, either as bare DNA or DNA encapsidated in an virus particle. Oneway that microorganism procure that vital DNA component for new qualities is by the formation of lysogens of temperate(mild) bacteriophage (e.g. Lambda Phage).

After infecting a host cell temperate phages settle on a decision for choosing lysogenic or lytic. If lysis is chosen, those involved in DNA replication and capsid production- lytic infection genes are expressed, as in any normal lytic infection cycle. if there is critical accumulation of a repressor for these lytic qualities, the phage DNA may integrate into the host chromosome. Once a temperate phage has turned out to be incorporated into the genome of the host cell, there will be a couple of prophage qualities expressed in the host cell. The declaration of prophage qualities can give the host cell new attributes, including resistance to reinection by a similar phage, or toxin production. The capacity of a prophage to give a host cell new attributes is called phage transformation.

Types of Bacteriophage Virulent Capable of causing infection and eventually destruction and death of the bacterial cell. These follow the lytic cycle.. T4 host E.coli. Temperat e Does not cause destruptic infection instead phage DNA is incorporated into bacterium DNA and is replicated with it and after some cycle become virulent cause lysis. lambda phage.

Discovered by : Transduction was first discovered in 1952 by Joshua Lederberg and Norton Zinder Studied system: Studied in Salmonella typhimurium Plated two auxotrophic strains (LA-2 and LA-22) individually on minimal medium, no cells grew. Plated a mixture of the two auxotrophic strains on minimal medium, cells grew into colonies. Thus, genetic exchange was taking place between the two cell types. Experiment through U-tube Experiment Performed U-tube experiment. Found that part of the cells on one side of the U-tube were prototrophs (could grow in minimal medium). Observed in Transduction has been found to occur in a variety of prokaryotes, including certain species of the Bacteria: Salmonella, Escherichia, Pseudomonas, Desulfovibrio, Rhodococcus, Rhodobacter, Staphylococcus, and Xanthobacter, as well as Methanobacterium thermoautotrophicum.

Transduction is the process by which foreign DNA is introduced into a cell by a virus or viral vector. Transduction is a common tool used by molecular biologists to stably introduce a foreign gene into a host cell's genome (both bacterial and mammalian cells). What is transduction ?

Transduction Generalized transduction: A bacterial virus, or bacteriophage, transfers the DNA from one bacterial cell to another During a LYTIC infection, a transducing phage, such as P1 infecting E. coli, accidentally packages a piece of the bacterial chromosome into a virus particle instead of its own viral DNA. The phage carrying the bacterial DNA then delivers it to the recipient cell when it tried to infect again. The injected bacterial DNA may then be inserted into recipient chromosome by homologous recombinant. Specialized transduction Produced particles with both phage and host DNA, linked in a single DNA molecule, from a specific region of the chromosome (E. coli phage ) Unlike the F plasmid that can incorporate anywhere in the E. coli genome, lambda can only incorporate into a specific site, called att λ. The gal gene is on one side of att λ and the bio gene (biotin synthesis) is on the other side. Sometimes when lambda come out of the chromosome at the end of the lysogenic phase, it crosses over at the wrong point. When this happens, a piece of the E. coli chromosome is incorporated into the lambda phage chromosome

Significance Altering the genetic characteristics through transfering genetic material. For example: In specialised transduction the gal gene, a cell lacking ability to metabolize galactose could aquire the ability. It shows the evolutionary relationship between the prophage and host bacterial cell. Prophage can exist in a cell for a long period suggests a similar possible mechanism for the viral origin of cancer. It provides a way to study the gene linkage