Regulation of Hexuronate Utilization in Bacillus subtilis

Abstract

ABSTRACT We have identified a locus essential for galacturonate utilization in Bacillus subtilis . Genes homologous to Escherichia coli and Erwinia chrysanthemi glucuronate and galacturonate metabolic genes were found in a cluster consisting of 10 open reading frames (ORFs) in the B. subtilis chromosome. A mutant of B. subtilis containing a replacement of the second and third ORFs was unable to grow with galacturonate as its primary carbon source. Galacturonate induced expression from a ς A -dependent promoter, exu P1, located upstream from the first ORF. The eighth ORF in this cluster (the exu locus) encodes a LacI and GalR homolog that negatively regulated expression from exu P1. A 26-bp inverted repeat sequence centered 15 bp downstream from the exu P1 start point of transcription acted in cis to negatively regulate expression from exu P1 under noninducing conditions. Expression from the exu P1 promoter was repressed by high levels of glucose, which is probably mediated by CcpA (catabolite control protein A). A ς E -dependent promoter, exu P2, was localized between the second and third ORFs and was active during sporulation.