Project description: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.
Project description:Shewanella oneidensis MR-1 was grown on electrodes in electrochemical flow cells (EFC), and the transcriptome profiles of electrode-attached MR-1 cells were compared under electrolyte-flow and static (non-flow) conditions. The results revealed that the SO_3096 gene encoding a putative extracytoplasmic function (ECF) sigma factor, as well as genes related to cyclic-di-guanosine monophosphate and flagella synthesis (e.g., SO_3556 and flrC) and c-type cytochrome maturation (dsbD), was significantly up-regulated under the electrolyte-flow condition. Compared to wild-type MR-1 (WT), a deletion mutant of SO_3096 (∆SO_3096) showed an impaired biofilm formation and a decreased current generation in EFC, suggesting that the ECF sigma factor encoded by this gene is involved in the regulation of biofilm formation and current generation under electrolyte-flow conditions. We also compared the transcriptome profiles of WT and ∆SO_3096 grown in EFC, confirming that many genes up-regulated under the electrolyte-flow condition, including dsbD, were down-regulated in ∆SO_3096. Transcription analysis using lacZ as a reporter gene showed that the promoter of dsbD is activated in the presence of SO_3096. Measurement of current generation by a dsbD-deletion mutant revealed that this gene is essential for electron transfer to electrodes. These results suggest that the SO_3096 protein serves as an ECF sigma factor that regulates cellular functions related to electroactive biofilm formation under electrolyte-flow conditions.
Project description:Shewanella oneidensis MR-1 was grown on electrodes in electrochemical flow cells (EFC), and the transcriptome profiles of electrode-attached MR-1 cells were compared under electrolyte-flow and static (non-flow) conditions. The results revealed that the SO_3096 gene encoding a putative extracytoplasmic function (ECF) sigma factor, as well as genes related to cyclic-di-guanosine monophosphate and flagella synthesis (e.g., SO_3556 and flrC) and c-type cytochrome maturation (dsbD), was significantly up-regulated under the electrolyte-flow condition. Compared to wild-type MR-1 (WT), a deletion mutant of SO_3096 (∆SO_3096) showed an impaired biofilm formation and a decreased current generation in EFC, suggesting that the ECF sigma factor encoded by this gene is involved in the regulation of biofilm formation and current generation under electrolyte-flow conditions. We also compared the transcriptome profiles of WT and ∆SO_3096 grown in EFC, confirming that many genes up-regulated under the electrolyte-flow condition, including dsbD, were down-regulated in ∆SO_3096. Transcription analysis using lacZ as a reporter gene showed that the promoter of dsbD is activated in the presence of SO_3096. Measurement of current generation by a dsbD-deletion mutant revealed that this gene is essential for electron transfer to electrodes. These results suggest that the SO_3096 protein serves as an ECF sigma factor that regulates cellular functions related to electroactive biofilm formation under electrolyte-flow conditions.