Project description:Members of the bacterial phylum Spirochaetes are primarily studied for their commensal and pathogenic roles in animal hosts. However, Spirochaetes are also frequently detected in anoxic hydrocarbon-contaminated environments but their ecological role in such ecosystems has so far remained unclear. Here we provide a functional trait to these frequently detected organisms with an example of a sulfate-reducing, naphthalene-degrading enrichment culture consisting of a sulfate-reducing deltaproteobacterium Desulfobacterium naphthalenivorans and a novel spirochete Rectinema cohabitans. Using a combination of genomic, proteomic, and physiological studies we show that R. cohabitans grows by fermentation of organic compounds derived from biomass from dead cells (necromass). It recycles the derived electrons in the form of H2 to the sulfate-reducing D. naphthalenivorans, thereby supporting naphthalene degradation and forming a simple microbial loop. We provide metagenomic evidence that equivalent associations between Spirochaetes and hydrocarbon-degrading microorganisms are of general importance in hydrocarbon- and organohalide-contaminated ecosystems. We propose that environmental Spirochaetes form a critical component of a microbial loop central to nutrient cycling in subsurface environments. This emphasizes the importance of necromass and H2-cycling in highly toxic contaminated subsurface habitats such as hydrocarbon-polluted aquifers.
Project description:A significant part of the heavier petroleum fraction resulting from offshore oil-spills sinks to the deep-sea. Its fate and biodegradation by microbial communities is unclear. In particular, the physiological and metabolic features of hydrostatic pressure (HP) adapted oil-degraders have been neglected. In this study, hydrocarbon-free sediment from 1km below surface water (bsl) was incubated at 0.1, 10 and 20MPa (equivalent to surface waters, 1 and 2km bsl) using triacontane (C30) as sole carbon source for a 3-month enrichment period. HP strongly impacted biodegration, as it selected for microbial communities with small cells, high O2 respiration and nutrients requirements, but low biomass and C30-degradation yields. The alkane-degrading metaproteome linked to β-oxidation was detected but its expression was reduced under HP contrary to several housekeeping genes. This was reflected in the enriched communities, as atmospheric pressure was dominated by hydrocarbonoclastic bacteria while non-specialized or previously unrecognized oil-degrading genera were enriched under HP.
Project description:Four stable and robust TCE-dechlorinating microbial communities were enriched from TCE-contaminated groundwater under four different conditions exploring two parameters, high and low methanogenic activity (Meth and NoMeth), with and without vitamin B12 supplement (MethB12 and NoMethB12, Meth and NoMeth, respectively). Identical amounts of lactate (2.7 mmol) and TCE (20 μl) were supplied as electron donor and electron acceptor. All four cultures were capable of reductively dechlorinating TCE to VC and ethene. Genomic DNA of the four enrichments was applied on a quad-Dhc-genome microarray in order to characterize the gene content of Dehalococcoides species present in the four enrichments
Project description:Four stable and robust TCE-dechlorinating microbial communities were enriched from TCE-contaminated groundwater under four different conditions exploring two parameters, high and low methanogenic activity (Meth and NoMeth), with and without vitamin B12 supplement (MethB12 and NoMethB12, Meth and NoMeth, respectively). Identical amounts of lactate (2.7 mmol) and TCE (20 M-NM-<l) were supplied as electron donor and electron acceptor. All four cultures were capable of reductively dechlorinating TCE to VC and ethene. Genomic DNA of the four enrichments was applied on a quad-Dhc-genome microarray in order to characterize the gene content of Dehalococcoides species present in the four enrichments The genomic DNA of four enrichment cultures completely dechlorinated TCE to VC and ethene was used on the microarray to query Dehalococcoides species present in the mixed cultures.
