Project description:Anaerobic digestion is a popular and effective microbial process for waste treatment. The performance of anaerobic digestion processes is contingent on the balance of the microbial food web in utilizing various substrates. Recently, co-digestion, i.e., supplementing the primary substrate with an organic-rich co-substrate has been exploited to improve waste treatment efficiency. Yet the potential effects of elevated organic loading on microbial functional gene community remains elusive. In this study, functional gene array (GeoChip 5.0) was used to assess the response of microbial community to the addition of poultry waste in anaerobic digesters treating dairy manure. Consistent with 16S rRNA gene sequences data, GeoChip data showed that microbial community compositions were significantly shifted in favor of copiotrophic populations by co-digestion, as taxa with higher rRNA gene copy number such as Bacilli were enriched. The acetoclastic methanogen Methanosarcina was also enriched, while Methanosaeta was unaltered but more abundant than Methanosarcina throughout the study period. The microbial functional diversity involved in anaerobic digestion were also increased under co-digestion.
Project description:Anaerobic activation of benzene is expected to represent a novel biochemistry of environmental significance but research into the mechanisms has been stymied by a lack of a genetically tractable pure culture which unequivocally does not use molecular oxygen to activate benzene. Geobacter metallireducens grew in a medium in which benzene was the sole electron donor and Fe(III) was the sole electron acceptor with a stoichiometry of benzene loss and Fe(III) reduction consistent with benzene oxidation to carbon dioxide coupled with Fe(III) reduction. Phenol labeled with 18O was produced when the medium was labeled with H218O, as expected for a true anaerobic conversion of benzene to phenol. Gene expression patterns indicated that benzene was metabolized through a phenol intermediate rather than benzoate or toluene. Deletion of ppcB, which encodes a subunit of the phenylphosphate carboxylase, an enzyme required for phenol metabolism, inhibited metabolism of benzene. Deleting genes specific for benzoate or toluene metabolism did not. Comparison of gene expression patterns in cells grown on benzene versus cells grown on phenol revealed genes specifically expressed in benzene-grown cells. Deletion of one of these, Gmet_3376, inhibited anaerobic benzene oxidation, but not the metabolism of phenol, benzoate, or toluene. The availability of a genetically tractable pure culture that can anaerobically convert benzene to phenol with oxygen derived from water should significantly accelerate elucidation of the mechanisms by which benzene can be activated in the absence of molecular oxygen.
Project description:This SuperSeries is composed of the following subset Series: GSE28549: Anaerobic Oxidation of Benzene by the Hyperthermophilic Archaeon Ferroglobus placidus (Phenol vs. Benzoate) GSE30798: Anaerobic Oxidation of Benzene by the Hyperthermophilic Archaeon Ferroglobus placidus (Benzene vs. Acetate) GSE30799: Anaerobic Oxidation of Benzene by the Hyperthermophilic Archaeon Ferroglobus placidus (Benzene vs. Phenol) GSE30801: Anaerobic Oxidation of Benzene by the Hyperthermophilic Archaeon Ferroglobus placidus (Benzene vs. Benzoate) Refer to individual Series