Project description:Polycyclic aromatic hydrocarbons (PAHs) are widely distributed pollutants. As in saturated PAH-contaminated sites oxygen is rapidly depleted, microorganisms able to use these compounds as a carbon source in the absence of molecular oxygen are crucial for their consumption. Here, we described the metabolic pathway for anaerobic degradation of phenanthrene by a sulfate-reducing enrichment culture (TRIP) obtained from a natural asphalt lake. The dominant organism of this culture belongs to the Desulfobacteraceae family of deltaproteobacteria. Proteogenome analysis revealed that the metabolic capacity of this bacterium includes the key enzymes for dissimilatory sulfate reduction, the Embden-Meyerhof-Parnas pathway, a complete tricarboxylic acid cycle as well as the key elements of the Wood-Ljungdahl pathway. Genes encoding enzymes potentially involved in the degradation of phenanthrene were identified in the genome of this bacterium. Two gene clusters were identified encoding a carboxylase enzyme involved in the activation of phenanthrene, as well as genes encoding reductases potentially involved in subsequent ring dearomatization and reduction steps. The predicted metabolic pathways were corroborated by transcriptome and proteome analyses and provide the first metabolic pathway for anaerobic degradation of three-rings PAHs.
Project description:Degradation of polycyclic aromatic hydrocarbons (PAHs) such as naphthalene by anaerobic microorganisms is poorly understood. Strain NaphS2, an anaerobic sulfate reducing marine delta-proteobacterium is capable of using naphthalene and the aromatic compound benzoate, as well as pyruvate, as an electron donors in the presence of sulfate. In order to identify genes involved in the naphthalene degradation pathway, we compared gene expression in NaphS2 during growth on benzoate vs. pyruvate, naphthalene vs. pyruvate, and naphthalene vs benzoate.
Project description:Pelobacter carbinolicus is phylogenetically intertwined with the Geobacteraceae, a family of deltaproteobacteria which couple oxidation of organic compounds to Fe(III) reduction. Whereas Geobacter species completely oxidize organic compounds to CO2, Pelobacter species either ferment or oxidize short chain alcohols to acetate. Pelobacter species also contain far fewer c-type cytochromes, proteins which play a role in electron transfer during Fe(III) respiration, compared to their Geobacter counterparts. Keywords: two-condition comparison
Project description:Pelobacter carbinolicus is phylogenetically intertwined with the Geobacteraceae, a family of deltaproteobacteria which couple oxidation of organic compounds to Fe(III) reduction. Whereas Geobacter species completely oxidize organic compounds to CO2, Pelobacter species either ferment or oxidize short chain alcohols to acetate. Pelobacter species also contain far fewer c-type cytochromes, proteins which play a role in electron transfer during Fe(III) respiration, compared to their Geobacter counterparts. Keywords: two-condition comparison Three biological replicates were hybridized in duplicate. Experimental (FeIII) was labeled with cy5, control (acetoin) was labeled with cy3.
Project description:Cable bacteria of the family Desulfobulbaceae form centimeter-long filaments comprising thousands of cells. They occur worldwide in the surface of aquatic sediments, where they connect sulfide oxidation with oxygen or nitrate reduction via long-distance electron transport. In the absence of pure cultures, we used single-filament genome amplification and metagenomics to retrieve draft genomes of three marine Candidatus Electrothrix and one freshwater Ca. Electronema species. These genomes contain >50% of unknown genes but still largely share their core genomic makeup with sulfate-reducing and sulfur-disproportionating Desulfobulbaceae, with few genes lost and 212 unique genes conserved among cable bacteria. Last common ancestor analysis indicated gene divergence and lateral gene transfer as equally important origins of these unique genes. With support from metaproteomic data of Ca. Electronema, the genomes suggest that cable bacteria oxidize sulfide by inversing the canonical sulfate reduction pathway and fix CO2 using the Wood-Ljungdahl pathway. Cable bacteria show limited organotrophic potential, may assimilate smaller organic acids and alcohols, fix N2, and synthesize polyphosphates and polyglucose as storage compounds; several of these traits were confirmed by cell-level experimental analyses. We propose a model for electron flow from sulfide to oxygen that involves periplasmic cytochromes, type IV pili as integral components of conductive periplasmic fibers, and periplasmic oxygen reduction. This model proposes that an active cable bacterium gains energy in the anodic, sulfide-oxidizing cells, while cells in the oxic zone flare off electrons through intense cathodic oxygen respiration without energy conservation; this peculiar form of multicellularity seems unparalleled in the microbial world.
Project description:Degradation of polycyclic aromatic hydrocarbons (PAHs) such as naphthalene by anaerobic microorganisms is poorly understood. Strain NaphS2, an anaerobic sulfate reducing marine delta-proteobacterium is capable of using naphthalene and the aromatic compound benzoate, as well as pyruvate, as an electron donors in the presence of sulfate. In order to identify genes involved in the naphthalene degradation pathway, we compared gene expression in NaphS2 during growth on benzoate vs. pyruvate, naphthalene vs. pyruvate, and naphthalene vs benzoate. For each experimental set, aRNA from NaphS2 was labelled Cy5 (experiment) or Cy3(control) with three biological replicates hybridized in duplicate. In addition, because of the size of the predicted genome of NaphS2, ORFs were divided into two separate array designs, designated set1 and set2, such that set1 and set2 represent two separate array designs (probe sets) to be treated separately in statistical analysis.
Project description:Propionate accumulation is an important bottleneck for anaerobic degradation of organic matter. We hypothesized that propionate conversion by a novel coculture of Syntrophobacter fumaroxidans and Geobacter sulfurreducens can be an alternative strategy for propionate oxidation coupled to Fe(III) reduction. In this study, we successfully cocultured S. fumaroxidans and G. sulfurreducens on propionate and Fe(III). Proteomic analyses of this coculture provided insights into the underlying mechanisms of propionate metabolism pathway and interspecies electron transfer mechanism. Our study can be further useful in understanding syntrophic propionate degradation in bioelectrochemical and anaerobic digestion systems.
Project description:Here, we established a successive Fe0-enhanced microbe system to remove azo dye (a typical organic pollutant) by Shewanella decolorationis S12 (S. decolorationis S12, an effective azo dye degradation bacterium) and examined the gene expression time course (10, 30, 60, and 120 min) in whole genome transcriptional level. Comparing with the treatment without ZVI, approximately 8% genes affiliated with 10 different gene expression profiles in S. decolorationis S12 were significantly changed in 120 min during the ZVI-enhanced microbial azo reduction. Intriguingly, MarR transcriptional factor might play a vital role in regulating ZVI-enhanced azo reduction in the aspect of energy production, iron homeostasis, and detoxification. Further investigation showed that induced [Ni-Fe] H2ase genes (hyaABCDEF) and azoreductase genes (mtrABC-omcA) contributed to ZVI-enhanced energy production, while reduced iron uptake (hmuVCB and feoAB), induced sulfate assimilation (cysPTWA) and cysteine biosynthesis (cysM) related genes were essential to iron homeostasis and detoxification. This study disentangles underlying mechanisms of ZVI-enhanced azo reduction in S. decolorationis S12 and lays a foundation for further optimization of integrated ZVI-microbial system for efficient organic pollution treatment.
Project description:Time-series transcriptional profiles of Shewanella oneidensis type strain MR-1 under iron depletion and repletion conditions. Iron homeostasis of Shewanella oneidensis, a gamma-proteobacterium possessing high iron content, is regulated by a global transcription factor Fur. However, knowledge is incomplete about other biological pathways that respond to changes in iron concentration, as well as details of the responses. In this work, temporal gene expression profiles were examined for iron depletion and repletion to delineate the iron response of S. oneidensis and a gene co-expression network was reconstructed. Modules of iron acquisition systems, anaerobic energy metabolism and protein degradation were the most noteworthy in the gene network. Bioinformatics analyses suggested that genes in each of the modules might be regulated by DNA-binding proteins Fur, CRP and RpoH, respectively. Closer inspection of these modules revealed a transcriptional regulator (SO2426) involved in iron acquisition and ten transcriptional factors involved in anaerobic energy metabolism. Selected genes in the network were analyzed by genetic studies. Disruption of genes encoding a putative alcaligin biosynthesis protein (SO3032) and a gene previously implicated in protein degradation (SO2017) led to severe growth deficiency under iron depletion conditions. Disruption of a novel transcriptional factor (SO1415) caused deficiency in both anaerobic iron reduction and growth with thiosulfate or TMAO as an electronic acceptor, suggesting that SO1415 is required for specific branches of anaerobic energy metabolism pathways. In conclusion, we identified major biological pathways that were differentially expressed during iron depletion and repletion. Four biological replicates of S. oneidensis MR-1 cells were grown to the midlog phase (OD600 = 0.6). Samples were collected at time 0, and then at 1, 5, 10, 20, 40, and 60 min after adding 2,2'-dipyridyl to attain a final concentration of 160 uM. Thereafter, ferrous sulfate was added to final concentration of 200 uM, and cells were collected at 1, 5, 10, 20, 40, and 60 min.
Project description:The aim of this RNA-sequencing study is to measure differential gene expression in 4 intestinal bacteria (Bacteroides xylanisolvens, Bacteroides thetaiotaomicron, Subdoligranulum variabile and Roseburia intestinalis). The data highlight the coordinated action of genes within the same locus involved in the degradation of complex carbohydrates. These loci are well characterized in Bacteroidetes species and referred to as polysaccharide utilization loci. In Firmicutes species, these loci are not so clear-cut, athough the GP-PUL concept has already been proposed. Here we compare the differential gene expression in minimal culture medium supplemented with a complex carbohydrate with a minimal culture medium supplemented with glucose. This differential analysis reveals a source-specific genetic response and a coordinated expression of genes involved in carbohydrate transport, carbohydrate degradation and transcriptional activation of these complex enzymatic machineries.