[Characteristics of sigL mutant in Bacillus thuringiensis HD-73]

The purpose of this study was to characterize sigL mutant in Bacillus thuringiensis (Bt) HD-73, and to determine the function of sigL gene of Bt.

We studied the growth speed of the sigL mutant and complementary strain in different nutrient medium with different amino acids as nitrogen source respectively. lacZ gene was fused with the promoter of the acoR gene and bkdR gene, and two recombined genes were expressed in sigL mutant strain and HD-73 wild strain sequentially.

sigL mutant could not grow on arginine, proline, valine, isoleucine, glutamine, phenylalanine, methionine and tryptophane as the sole nitrogen source separately. Activity of beta-galactosidase in sigL mutant strain was much lower than it in wild-type strain and sequence analysis showed that the domain of AcoR and BkdR are similar to the conserved domain of SigL-dependent transcriptional activator in Bt.

The deletion of sigL gene maybe blocked some important metabolic pathways. AcoR and BkdR are sigma L-dependent transcriptional activators in Bacillus thuringiensis strains, probably the operons which were regulated by AcoR and BkdR were also controlled by sigma L respectively.