Mc. Renna et al., REGULATION OF THE BACILLUS-SUBTILIS ALSS, ALSD, AND ALSR GENES INVOLVED IN POST-EXPONENTIAL-PHASE PRODUCTION OF ACETOIN, Journal of bacteriology, 175(12), 1993, pp. 3863-3875
Acetoin is a major extracellular product of Bacillus subtilis grown on
glucose and other fermentable carbon sources. The enzymes responsible
for the formation of acetoin, acetolactate synthase, and acetolactate
decarboxylase are synthesized in detectable amounts only in cells tha
t have reached stationary phase. We have cloned and sequenced the gene
s encoding these enzymes, alsS and alsD, as well as a gene, alsR, that
regulates their expression. alsS and alsD appear to compose a single
operon, while alsR is transcribed divergently from the alsSD operon. A
lsR shows significant homology to the LysR family of bacterial activat
or proteins, and when alsR is disrupted the alsSD operon is not expres
sed. Transcriptional fusions to alsS and alsR revealed that AlsR is re
quired for the transcription of the alsSD operon, which increases duri
ng stationary phase. Two mutations that cause increased expression of
the alsSD operon have been isolated, cloned, and sequenced. They each
change an amino acid in the AlsR protein.