An AraC-like transcriptional activator is required for induction of genes needed for alpha-galactoside utilization in Sinorhizobium meliloti.

The nodulating bacterium Sinorhizobium meliloti can utilize alpha-galactosides like melibiose and raffinose as sole sources of carbon and energy. We show that this utilization requires an AraC-like transcriptional activator, AgpT. When agpT was inactivated, Rhizobium meliloti could not utilize alpha-galactosides or induce genes required for transport and catabolism of these sugars. The agpT gene was not essential for the establishment of an effective nitrogen-fixing symbiosis.