Bacillus subtilis genes for the utilization of sulfur from aliphatic sulfonates

Abstract

A 5 kb region upstream of katA at 82°G on the Bacillus subtilis chromosome contains five ORFs organized in an operon-like structure. Based on sequence similarity, three of the ORFs are likely to encode an ABC transport system (ssuBAC) and another to encode a monooxygenase (ssuD). The deduced amino acid sequence of the last ORF (ygaN) shows no similarity to any known protein. B. subtilis can utilize a range of aliphatic sulfonates such as alkanesulfonates, taurine, isethionate and sulfoacetate as a source of sulfur, but not when ssuA and ssuC are disrupted by insertion of a neomycin-resistance gene. Utilization of aliphatic sulfonates was not affected in a strain lacking 3′-phosphoadenosine 5′-phosphosulfate (PAPS) sulfotransferase, indicating that sulfate is not an intermediate in the assimilation of sulfonate-sulfur. Sulfate or cysteine prevented expression of β-galactosidase from a transcriptional ssuD::IacZ fusion. It is proposed that ssuBACD encode a system for ATP-dependent transport of alkanesulfonates and an oxygenase required for their desulfonation.