CpdA is involved in amino acid metabolism in Shewanella oneidensis MR-1

Cyclic 3′,5′-adenosine monophosphate (cAMP) phosphodiesterase (CPD) is an enzyme that catalyzes the hydrolysis of cAMP, a signaling molecule affecting diverse cellular and metabolic processes in bacteria. Some CPDs are also known to function in cAMP-independent manners, while their physiological roles remain largely unknown. Here, we investigated physiological roles of CPD in Shewanella oneidensis MR-1, a model environmental bacterium, and report that CPD is involved in amino-acid metabolism. We found that a CPD-deficient mutant of MR-1 (ΔcpdA) showed decreased expression of genes for the synthesis of methionine, S-adenosylmethionine, and histidine and required these three compounds to grow in minimal media. Interestingly, deletion of adenylate cyclases in ΔcpdA did not restore the ability to grow in minimal media, indicating that the amino acid requirements were not due to the accumulation of cAMP. These results suggest that CPD is involved in the regulation of amino acid metabolism in MR-1 in a cAMP-independent manner.

cAMP and cGMP levels and growth rates of cells aerobically grown in lactate minimal medium are shown in panels A, B, and C, respectively.