The Role of Alternative Sigma Factors in Pathogen Virulence

Alternative sigma factors enable bacteria to change the promoter specificity of the core RNA polymerase to enable the expression of genes that give them advantages in particular situations. The number of alternative sigma factors that bacteria produce varies greatly. Some bacteria, particularly those that reside in the soil have genes for multiple sigma factors. The soil living gram positive bacteria Sorangium cellulosum currently holds the record for the number of sigma factor genes at 109. Alternative sigma factors play important roles in the life cycle of many foodborne bacterial pathogens. In this review we will discuss: the structure and function of alternative sigma factors; the different families of alternative sigma factors; their regulation; the role of particular alternative sigma factors and the genes they control in the biology (particularly pathogenesis) of foodborne bacterial pathogens.