We have identified a locus essential for galacturonate utilization in Bacil
lus subtilis. Genes homologous to Escherichia coli and Erwinia chrysanthemi
glucuronate and galacturonate metabolic genes were found in a cluster cons
isting of 10 open reading frames (ORFs) in the B. subtilis chromosome, A mu
tant of B. subtilis containing a replacement of the second and third ORFs w
as unable to grow with galacturonate as its primary carbon source. Galactur
onate induced expression from a sigma(A)-dependent promoter, exuP1, 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
exuP1, A 26-bp inverted repeat sequence centered 15 bp downstream from the
exuP1 start point of transcription acted in cia to negatively regulate exp
ression from exuP1 under noninducing conditions. Expression from the exuP1
promoter was repressed by high levels of glucose, which is probably mediate
d by CcpA (catabolite control protein A). A sigma(E)-dependent promoter, ex
uP2, was localized between the second and third ORFs and was active during
sporulation.