Project description:The Geobacter species evolved respiratory versatility to utilize a wide range of terminal electron acceptors. To explore this adaptive mechanism, Fe(III) citrate, hydrous ferric oxide, and fumarate were selected as electron acceptors, and the methylome and metabolome of Geobacter sulfurreducens PCA grown on each electron acceptor were investigated via third-generation, single-molecule real-time DNA sequencing.Results showed that the patterns of 4-methylcytosine (m4C) and 6-methyladenine (m6A) modification were all varied in different electron acceptor cultures. Moreover, genes (e.g., GSU0466 and GSU1467) with low expression levels generally had high methylation levels. These findings suggest that m4C and m6A modifications play a role in the adaption of G. sulfurreducens to diverse electron acceptors, and DNA methylation may be involved in the adaption mainly via gene expression regulation.
Project description:We report the effects of two metabolites alpha-ketobutyrate and pyruvate on transcription of K562 cells. Increased cell size associates with electron acceptor limitation. Using four replicates per condition, we find that electron acceptors alleviate endoplasmic reticulum stress response in these cells as evidenced by reduction of amino acid transporter as well as ATF4 and CHOP expression.
Project description:Geobacter sulfurreducens has a complex metabolism that adapts to use electron acceptors at a wide range of redox potentials. In this study, we used RNA-seq to identify genes associated with electron transfer pathways at different redox potentials. By correlating the RNA-seq data with cyclic voltammetry, we associated several multiheme cytochromes with specific electron transfer pathways.
Project description:Alicycliphilus denitrificans is a versatile, ubiquitous, facultative anaerobic bacterium. A. denitrificans strain BC can use chlorate, nitrate and oxygen as electron acceptor for growth. Cells display a prolonged lag-phase when transferred from nitrate to chlorate and vice versa. Furthermore, cells adapted to aerobic growth do not easily use nitrate or chlorate as electron acceptor. We further investigated these responses of strain BC by differential proteomics, transcript analysis and enzyme activity assays. In nitrate-adapted cells transferred to chlorate and vice versa, appropriate electron acceptor reduction pathways need to be activated. In oxygen-adapted cells, adaptation to the use of chlorate or nitrate is likely difficult due to the poorly active nitrate reduction pathway and low active chlorate reduction pathway. We deduce that the Nar-type nitrate reductase of strain BC also reduces chlorate, which may result in toxic levels of chlorite if cells are transferred to chlorate. Furthermore, the activities of nitrate reductase and nitrite reductase appear to be not balanced when oxygen-adapted cells a shifted to nitrate as electron acceptor, leading to the production of a toxic amount of nitrite. These data suggest that strain BC encounters metabolic challenges in environments with fluctuations in the availability of electron acceptors. Proteomic samples were prepared from Alicycliphilus denitrificans grown in the presence of different electron acceptors: chlorate, nitrate and oxygen. Proteins were separated by a short SDS gel and for each sample 4 in-gel digest slices were prepared. Peptide samples were measured by nLC LTQ-Orbitrap and the data were analysed with MaxQuant using default settings (1% FDR on peptide and protein level) and filtered extra to keep only proteins identified with at least 2 peptides and 1 unique and 1 unmodified peptide.
Project description:We demonstrate the feasibility of total RNA-SIP in experiments where microbes from a hydrocarbon-contaminated aquifer were studied in microcosms with 13C-labelled-toluene to understand their adaptation to the simultaneous availability of low levels of different electron acceptors. SIP successfully resolved the involvement of microaerobic vs. aerobic and anaerobic populations. Under microoxic, nitrate-amended conditions hydrocarbon degradation was actually stimulated, but transcripts of denitrification showed no signs of 13C-labelling. The expression of distinct oxygenase-based catabolic pathways for toluene degradation was clearly apparent in 13C-labelled mRNA. We discuss how these direct insights into the gene expression and adaptation mechanisms within complex degrader communities can guide more integrated approaches in monitoring and restoration of contaminated sites.
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.
Project description:Bioavailability of electron acceptors is probably the most limiting factor in the restoration of anoxic, contaminated environments. The oxidation of contaminants such as aromatic hydrocarbons, particularly in aquifers, often depends on the reduction of ferric iron or sulphate. We have previously detected a highly active fringe zone beneath a toluene plume at a tar-oil contaminated aquifer in Germany, where a specialized community of contaminant degraders co-dominated by Desulfobulbaceae and Geobacteraceae had established. Although on-site geochemistry links degradation to sulphidogenic processes, dominating catabolic (benzylsuccinate synthase alpha-subunit, bssA) genes detected in situ appeared more related to those of Geobacter spp. Therefore, a stable isotope probing (SIP) incubation of sediment samples with 13C7-toluene and comparative electron acceptor amendment was performed. We introduce pyrosequencing of templates from SIP microcosms as a powerful new strategy in SIP gradient interpretation (Pyro-SIP). Our results reveal the central role of Desulfobulbaceae for sulphidogenic toluene degradation in situ, and affiliate the detected bssA genes to this lineage. This, and the absence of 13C-labelled DNA of Geobacter spp. in SIP gradients preclude their relevance as toluene degraders in situ. In contrast, Betaproteobacteria related to Georgfuchsia spp. became labelled under iron-reducing conditions. Furthermore, secondary toluene degraders belonging to the Peptococcaceae detected in both treatments suggest the possibility of functional redundancy amongst anaerobic toluene degraders on site. 2 samples examined from the different electron-acceptors (sulphate or ferric iron) incubates at the time point of maximal toluene degradation.
Project description:S. oneidensis MR-1 was grown with different electron acceptors: an electrode at 0.4 V vs. SHE, 50 mM Fe(III)citrate, and oxygen. The gene expression pattern for each experiment was analyzed and the differences in gene expression for the different experimental conditions were compared.