Under stress conditions, microorganisms have developed signal transduction systems (movement of signals from the cell to inside) to sense environmental stresses and to control the coordinated expression of genes involved in cellular defense mechanisms (Kennelly and. Potts 1996). These evolved protective or adaptive networks assist microorganisms to modify their environments and / or to survive the stress condition. A common regulatory mechanism involves sigma factors. Sigma factors are small proteins that bind to RNA polymerase (RNAP. The core RNAP has 5 components or subunits 2, and order to bind promoter-specific regions, the core enzyme requires another subunit, a sigma factor (o). The sigma factor. greatly reduces the affinity of RNAP for nonspecific Dna while increasing specificity for certain promoter regions, depending on the factor A sigma factor is normally present as part of the RNA polymerase