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.
Project description:The deep marine subsurface is one of the largest unexplored biospheres on Earth, where members of the phylum Chloroflexi are abundant and globally distributed. However, the deep-sea Chloroflexi have remained elusive to cultivation, hampering a more thorough understanding of their metabolisms. In this work, we have successfully isolated a representative of the phylum Chloroflexi, designated strain ZRK33, from deep-sea cold seep sediments. Phylogenetic analyses based on 16S rRNA genes, genomes, RpoB and EF-tu proteins indicated that strain ZRK33 represents a novel class within the phylum Chloroflexi, designated Sulfochloroflexia. We present a detailed description of the phenotypic traits, complete genome sequence and central metabolisms of the novel strain ZRK33. Notably, sulfate and thiosulfate could significantly promote the growth of the new isolate, possibly through accelerating the hydrolysis and uptake of saccharides. Thus, this result reveals that strain ZRK33 may play a crucial part in sulfur cycling in the deep-sea environments. Moreover, the putative genes associated with assimilatory and dissimilatory sulfate reduction are broadly distributed in the genomes of 27 metagenome-assembled genomes (MAGs) from deep-sea cold seep and hydrothermal vents sediments. Together, we propose that the deep marine subsurface Chloroflexi play key roles in sulfur cycling for the first time. This may concomitantly suggest an unsuspected availability of sulfur-containing compounds to allow for the high abundance of Chloroflexi in the deep sea.
Project description:This study investigates temporal dynamics in microbial community function within the freshwater ecosystem of Lake Zurich, Switzerland, over three months (36 timepoints). Metagenome-assembled genomes (MAGs) and metaproteomes were analyzed to identify species-specific and community-level protein expression patterns. The study explores how bacterial species contribute to ecosystem functioning through protein-level activity, focusing on relationships between species taxonomy, abundance, and protein investment patterns.
