Project description:5' RNASeq of mRNA from Shewanella loihica PV-4 grown aerobically in Luria-Bertani broth (LB) and defined lactate minimal medium 5'-end mRNA profiles of mid-log phase bacterial cells growing in LB or lactate medium were generated by next-generation sequencing.
Project description:The microarray experiment compare the transcriptome of PV-4 wild type versus the deltahemH1 mutant, a PPIX accumulating strain. Only part of the data is used in the manuscript and we are working on this dataset for future manuscripts
Project description:The microarray experiment compare the transcriptome of PV-4 wild type versus the deltahemH1 mutant, a PPIX accumulating strain. Only part of the data is used in the manuscript and we are working on this dataset for future manuscripts The wild type and deltahemH1 cell were revived and then cultured into late log-phase for collection, when significant PPIX accumulation occurred. Three biological replicates for wild type and deltahemH1
Project description:Although members of the genus Shewanella have common features (e.g., the presence of decaheme c-type cytochromes [c-cyts]), they are widely variable in genetic and physiological features. The present study compared the current-generating ability of S. loihica PV-4 in microbial fuel cells (MFCs) with that of well-characterized S. oneidensis MR-1 and examined the roles of c-cyts in extracellular electron transfer. We found that strains PV-4 and MR-1 exhibited notable differences in current-generating mechanisms. While the MR-1 MFCs maintained a constant current density over time, the PV-4 MFCs continued to increase in current density and finally surpassed the MR-1 MFCs. Coulombic efficiencies reached 26% in the PV-4 MFC but 16% in the MR-1 MFCs. Although both organisms produced quinone-like compounds, anode exchange experiments showed that anode-attached cells of PV-4 produced sevenfold more current than planktonic cells in the same chamber, while planktonic cells of MR-1 produced twice the current of the anode-attached cells. Examination of the genome sequence indicated that PV-4 has more c-cyt genes in the metal reductase-containing locus than MR-1. Mutational analysis revealed that PV-4 relied predominantly on a homologue of the decaheme c-cyt MtrC in MR-1 for current generation, even though it also possesses two homologues of the decaheme c-cyt OmcA in MR-1. These results suggest that current generation in a PV-4 MFC is in large part accomplished by anode-attached cells, in which the MtrC homologue constitutes the main path of electrons toward the anode.
Project description:Determining the function and regulation of paralogues is important in understanding microbial functional genomics and environmental adaptation. Heme homeostasis is crucial for the survival of environmental microorganisms. Most Shewanella species encode two paralogues of ferrochelatase, the terminal enzyme in the heme biosynthesis pathway. The function and transcriptional regulation of two ferrochelatase genes, hemH1 and hemH2, were investigated in Shewanella loihica PV-4. The disruption of hemH1 but not hemH2 resulted in a significant accumulation of extracellular protoporphyrin IX (PPIX), the precursor to heme, and decreased intracellular heme levels. hemH1 was constitutively expressed, and the expression of hemH2 increased when hemH1 was disrupted. The transcription of hemH1 was regulated by the housekeeping sigma factor RpoD and potentially regulated by OxyR, while hemH2 appeared to be regulated by the oxidative stress-associated sigma factor RpoE2. When an oxidative stress condition was mimicked by adding H2O2 to the medium or exposing the culture to light, PPIX accumulation was suppressed in the ?hemH1 mutant. Consistently, transcriptome analysis indicated enhanced iron uptake and suppressed heme synthesis in the ?hemH1 mutant. These data indicate that the two paralogues are functional in the heme synthesis pathway but regulated by environmental conditions, providing insights into the understanding of bacterial response to environmental stresses and a great potential to commercially produce porphyrin compounds.Shewanella is capable of utilizing a variety of electron acceptors for anaerobic respiration because of the existence of multiple c-type cytochromes in which heme is an essential component. The cytochrome-mediated electron transfer across cellular membranes could potentially be used for biotechnological purposes, such as electricity generation in microbial fuel cells and dye decolorization. However, the mechanism underlying the regulation of biosynthesis of heme and cytochromes is poorly understood. Our study has demonstrated that two ferrochelatase genes involved in heme biosynthesis are differentially regulated in response to environmental stresses, including light and reactive oxygen species. This is an excellent example showing how bacteria have evolved to maintain cellular heme homeostasis. More interestingly, the high yields of extracellular protoporphyrin IX by the Shewanella loihica PV-4 mutants could be utilized for commercial production of this valuable chemical via bacterial fermentation.
Project description:Shewanella spp. possess a broad respiratory versatility, which contributes to the occupation of hypoxic/anoxic environmental or host-associated niches. Here we observed a strain-specific induction of biofilm formation in response to supplementation with the anaerobic electron acceptors dimethyl sulfoxide (DMSO) and nitrate in a panel of Shewanella algae isolates. The respiration-driven biofilm response is not observed in DMSO and nitrate reductase deletion mutants of the type strain S. algae CECT 5071, and can be restored upon complementation with the corresponding reductase operon(s) but not by an operon containing a catalytically inactive nitrate reductase. The distinct transcriptional changes, proportional to the effect of these compounds on biofilm formation, include cyclic di-GMP (c-di-GMP) turnover genes. In support, ectopic expression of the c-di-GMP phosphodiesterase YhjH of Salmonella Typhimurium but not its catalytically inactive variant decreased biofilm formation. The respiration-dependent biofilm response of S. algae may permit differential colonization of environmental or host niches.