Formation of lambda specialized transducing phage


Because lambda is packaged by a headful mechanism, specialized transducing phage that carry a small region of the bacterial chromosome lack a corresponding amount of phage DNA. The phage DNA that is missing corresponds to the opposite side ofthe prophage genome. Phage that carry the gal genes located on the left side of the prophage lack the phage genes required for lytic functions (e.g. the tail genes) that are located on the right side of the prophage, and phage that carry the bio genes located on the right side of the prophage lack the phage genes required for lysogeny functions (e.g. the int gene) that are located on the right side of the prophage.

Specialized transducing phage that carry genes located on the left side of the prophage (e.g. lambda dgal) are proficient for lysogeny but deficient for lysis. These phage require a helper phage to lyse a recipient cell (e.g. a wild-type lambda phage that provides the missing functions in trans). The "d" written in front of gal indicates that the phage is defective for lytic growth.

Specialized transducing phage that carry genes located on the right side of the prophage (e.g. lambda bio) are proficient for lysis but deficient for lysogeny. These phage can infect a recipient cell and generate a lysate, but require a helper phage to form lysogens a recipient cell (e.g. a wild-type lambda phage that provides the missing functions in trans). (Because they have all the functions required for lytic growth, there is no "d" written in front of bio.)

These are examples of specialized transducing phage resulting from integration of phage lambda at its primary attachment site (attB) on the E. coli chromosome. However, specialized transducing phage can be produced by analogous mechanisms by phage integrated at other sites as well (for example, lambda integrated at secondary attachment sites or other temperate phage integrated at their particular attachment sites.


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Last modified November 26, 2003