The soil bacterium ) has the ability to produce the alternative exopolysaccharide galactoglucan (EPS II) in addition to succinoglycan (EPS I). In the wild-type strain EPS II production is induced by phosphate-limiting conditions or by extra copies of the gene cluster. Based on similarities to transcriptional regulators of the MarR family, an additional putative regulatory gene, was identified in the gene cluster. Using transcriptional fusions, a stimulating effect of extra copies of this gene on the transcription of all complementation groups was determined. Phosphate limitation also resulted in increased expression of the fusions. This increase was reduced in strains characterized by a deletion of The previously reported high level of gene transcription in a mutant was further elevated under phosphate-limiting conditions. The and promoters contain sequences with similarities to the PHO box known as the PhoB-binding site in phosphate-regulated promoters in The gene was required for the activation of gene expression under phosphate limitation, but not for induction of expression by MucR or ExpG.


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