Sporulation-specific expression of the yvgW (cadA) gene and the effect of blockage on spore properties in Bacillus subtilis

The yvgW gene of Bacillus subtilis has been reported to encode a product which resembles CPx-type ATPase having a function related to Cd²⁺ and Zn²⁺ resistance through efflux of this metal. We recently showed that yvgW gene product is also important for sporulation in B. subtilis. The present study was focused on the functional characterization of yvgW in the sporulation process of B. subtilis. The analysis of yvgW expression showed that a significant expression took place during the late stage of sporulation (T₅-T₈). The deletion of spoIIAC and spoIIGB genes, encoding for σ^F and σ^E, respectively, resulted in the complete elimination of yvgW-lacZ expression while the deletion of the spoIIIG coding for σ^G decreased the yvgW-lacZ expression to only 37% that of the wild type level. In contrast, the deletion of spoIVCB gene coding for σ^K had no significant effects on the yvgW-lacZ expression. Transcription initiation site of yvgW during sporulation was determined by 5′-RACE-PCR, indicating that - 10 and - 35 sequences exhibited very good homology with the consensus sequences recognized by RNA polymerase containing σ^E. Moreover, through the construction of yvgWΔ537-1351::spc, yvgW mutant cells were investigated for their spore properties, such as their resistance profiles against heat, chloroform and lysozyme, pointing out that spores of the mutant cells showed high sensitivity to heat and chloroform, but resistance to lysozyme. The level of dipicolinic acid was also significantly reduced to approximately 63% in yvgW spores as compared to wild type spores. Furthermore, the analyses of the nutrition-specific germination and outgrowth characteristics of the null mutant and the wild type cells revealed no defect in the initiation of yvgW spore germination but they returned to vegetative state more slowly than the wild type spores in minimal medium.