Relative Roles of the fla/che PA, PD-3, and PsigD Promoters in Regulating Motility and sigD Expression in Bacillus subtilis

AUTOR(ES)

West, Joyce T.

FONTE

American Society for Microbiology

RESUMO

Three promoters have been identified as having potentially important regulatory roles in governing expression of the fla/che operon and of sigD, a gene that lies near the 3′ end of the operon. Two of these promoters, fla/che PA and PD-3, lie upstream of the >26-kb fla/che operon. The third promoter, PsigD, lies within the operon, immediately upstream of sigD. fla/che PA, transcribed by EςA, lies ≥24 kb upstream of sigD and appears to be largely responsible for sigD expression. PD-3, transcribed by EςD, has been proposed to participate in an autoregulatory positive feedback loop. PsigD, a minor ςA-dependent promoter, has been implicated as essential for normal expression of the fla/che operon. We tested the proposed functions of these promoters in experiments that utilized strains that bear chromosomal deletions of fla/che PA, PD-3, or PsigD. Our analysis of these strains indicates that fla/che PA is absolutely essential for motility, that PD-3 does not function in positive feedback regulation of sigD expression, and that PsigD is not essential for normal fla/che expression. Further, our results suggest that an additional promoter(s) contributes to sigD expression.

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