Project description:<p>A variety of anthropogenic organohalide contaminants generated from industry are released into the environment, and thus cause serious pollution that endangers human health. In the present study, we investigated the microbial community composition of industrial saponification wastewater using 16S rRNA sequencing, providing genomic insights of potential organohalide dehalogenation bacteria (OHDBs) by whole-metagenome sequencing. We also explored yet-to-culture OHDBs involved in the microbial community. Microbial diversity analysis reveals that Proteobacteria and Patescibacteria phyla dominate microbiome abundance of the wastewater. In addition, a total of six bacterial groups (Rhizobiales, Rhodobacteraceae, Rhodospirillales, Flavobạcteriales, Micrococcales, and Saccharimonadales) were found as biomarkers in the key organohalide removal module. Ninety-four metagenome-assembled genomes (MAGs) were reconstructed from the microbial community, and 105 hydrolytic dehalogenase genes within 42 MAGs were identified, suggesting that the potential for hydrolytic organohalide dehalogenation is present in the microbial community. Subsequently, we characterized the organohalide dehalogenation of an isolated OHDB, Microbacterium sp. J1-1, which shows the dehalogenation activities of chloropropanol, dichloropropanol, and epichlorohydrin. This study provides a community-integrated multi-omics approach to gain functional OHDBs for industrial organohalide dehalogenation.</p>
Project description:Lignin is the most abundant renewable source of aromatic carbon and its microbial depolymerization and metabolism under aerobic conditions is well studied. However, lignin breakdown in the absence of oxygen remains poorly understood. Here, we established long-term bacterial enrichment cultures supplied with diverse lignins as the sole carbon source under denitrifying conditions. Denitrification dynamics were followed by monitoring nitrogenous gases. Metagenomics analysis recovered 62 metagenome-assembled genomes (MAGs), several of which encoded enzymes for both denitrification and anaerobic metabolism of aromatic compounds. Quantitative metaproteomics confirmed expression of such enzymes and additionally showed that several MAGs expressed redox-active auxiliary-activity enzymes and other uncharacterised proteins that are potential candidates for involvement in lignin depolymerisation. The detection of several oxygen-dependent oxidoreductases despite anaerobic conditions prompt intriguing discussion of potential mechanistic explanations. This systems-level study expands our understanding of lignin turnover in anaerobic environments by bacteria and suggest enzymatic targets for further exploration of their role in lignin depolymerization under oxygen-limited conditions.
