Mxd expression in S. oneidensis MR-1 wild type. Mxd expression in S. oneidensis MR-1 wild type cells exposed to carbon and nitrogen starvation conditions. Wild type cells carrying the mxd promoter transcriptionally fused to lacZ were grown under complex medium conditions to mid-exponential phase. Cells were pelleted and the supernatant was discarded. Subsequently, cells were either resuspended in minimal medium containing no carbon source (MM minus carbon, or in minimal medium amended with 50 mM sodium lactate (MM plus carbon), or in minimal medium with the nitrogen source omitted (MM minus nitrogen). A set of control samples (black bars) was pelleted and resuspended in the same medium. Samples were assayed for β-galactosidase activity. Data represent an average of three independent experiments.