Shiga Toxin-encoding Phages: Multifunctional Gene Ferries
Maite Muniesa and Herbert Schmidt
from: Pathogenic Escherichia coli: Molecular and Cellular Microbiology (Edited by: Stefano Morabito). Caister Academic Press, U.K. (2014)
Shiga toxin encoding-bacteriophages (Stx-phages) constitute a heterogeneous group of temperate lambdoid phages that harbor Shiga toxin (stx) genes. The (stx genes are located in the late region of the prophage genome and expression of Stx is under phage control. In their lysogenic state, Stx-phages are incorporated in the bacterial genome at different chromosomal insertion sites. The presence of more than one Stx-phage in the same bacterial genome has implications in the expression of Stx and in the virulence of the respective host strain. Induction of Stx-phages is stimulated by activation of the lytic cycle, either by inducing agents or spontaneously, and this triggers increased production of Stx. Free Stx-phages are found in many environments, therefore being considered as vehicles that mobilize (stx by infection and lysogenization of bacteria in vivo and in vitro. This may lead to the emergence of new bacterial pathogens. Stx-phages can acquire and mobilize foreign genes, including virulence genes present in the chromosome of Escherichia coli strains. The role of Stx-phages in horizontal gene transfer, and their impact on bacterial virulence, have been intensively studied, but their biological impact is not yet completely understood read more ...