Project description:In this study we used metaproteomics to discern the metabolism and physiology of the microorganisms occurring in the phototrophic mats of four soda lakes in the interior of British Columbia, Canada. Binned and assembled metagenomes were used as the database for protein identification.
Project description:A new haloalkaliphilic species of Wenzhouxiangella, strain AB-CW3 was isolated from a system of alkaline soda lakes in the Kulunda Steppe. Its complete, circular genome was assembled from combined nanopore and illumina sequencing and its proteome was determined for three different experimental conditions: growth on Staphylococcus cells, casein, or peptone. AB-CW3 is an aerobic bacterium feeding mainly on proteins and peptides.
Project description:Despite cultivation of many representatives of rich bacterial communities inhabiting alkaline soda lakes, members of the bacterial phylum Verrucomicrobiota have so far been detected only by molecular techniques. Here, we used alginate as a selective substrate to enrich and isolate two strains of haloalkaliphilic Verrucomicrobiota. The isolates share identical 16S rRNA gene sequences and represent a new genus, and, together with metagenome assembled genomes, a new family within Opitutales. Cells of strains AB-alg1T (from soda lakes) and AB-alg4 (from soda soils) are small motile cocci forming submerged colonies in soft alginate agar. They are saccharolytic heterotrophs growing aerobically on polysaccharides (alginate, starch and inulin) and sugars (glucose, fructose, mannose, sucrose, melezitose, maltose and cellobiose). They also grow anaerobically by fermentation of alginate and D-mannose and by coupling incomplete denitrification to oxidation of alginate. Both isolates are obligately alkaliphilic and moderately salt-tolerant. The dominant membrane phospholipids include phosphatidylcholine and cardiolipin. The genome of AB-alg1T features polysaccharide lyases of the PL6, 7, 15, 17, 38, and 39 families for depolymerization of alginate. On the basis of phenotypic and distinct phylogeny, we propose classification of strains AB-alg1T (JCM 35393T=UQM 41574T) and AB-alg4 as Verruconatronum alginilyticum gen. nov., sp. nov. within a new family Verruconatronumaceae.
Project description:Anthropogenic activities such as urbanization and agriculture can potentially pose a threat to neighboring freshwaters through nitrate and phosphorous contamination, which over time may lead to lake eutrophication. In such nitrogen-polluted environments, oxygen is depleted, and plants die and decompose. This enhances denitrifying microbes that respire under hypoxic/anoxic conditions by reducing nitrate instead of molecular oxygen and using plant remnants (lignocellulose) as carbon source. Microbial lignocellulose degradation has been well-studied for both aerobic- and anaerobic conditions; however, its degradation during denitrification remains largely unknown. Here we have applied a combination of gas kinetics and meta-omics techniques to enrich and analyze microbial communities from 10 eutrophic lakes to identify a set of core microbial metagenome-assembled genomes (MAGs) present in all the eutrophic lakes. We have further investigated their strategies and enzyme profiles for degrading lignocellulose under denitrifying conditions. We identified Pseudomonadota, Bacteroidota, Verrucomicrobiota, and Actinomycetota as the most abundant phyla and they were present in enrichments from all eutrophic lakes having a key role in denitrification and fermentation. Lignocellulose degradation was, however, dominated by species outside the core microbiome, i.e., there were differing key degraders between lakes, suggesting some level of lake-specialization. Among these we observed potential respiratory DNRA pathways, and they expressed a broad range of CAZymes targeting the various lignocellulose subfractions. Interestingly, many of the detected MAGs contained NO dismutases, enzymes postulated to convert NO to molecular oxygen and dinitrogen gas.
Project description:Haloalkaliphilic microorganisms are double extremophiles functioning optimally at high salinity and pH. Their typical habitats are soda lakes, representing geologically ancient ecosystems which are still widespread on Earth and supposedly harbor relict microbial communities. We compared metabolic features and their genomic determinants in two strains of a single natronophilic species Dethiobacter alkaliphilus, the only cultured representative of “Dethiobacteria” class within Bacillota phylum. The strains of D. alkaliphilus were previously isolated from geographically remote Mongolian and Kenyan soda lakes. The type strain AHT1T was described as a facultatively chemolithoautotrophic sulfidogen reducing or disproportionating sulfur or thiosulfate, while strain Z-1002 was isolated as a chemolithoautotrophic iron reducer. Here, we uncovered iron reducing ability of strain AHT1T, as well as the capability of strain Z-1002 for thiosulfate reduction and anaerobic Fe(II) oxidation. Key catabolic processes sustaining the growth of both strains appeared to fit the geochemical settings of two contrasting natural alkaline environments, sulfur-enriched soda lakes and iron-enriched serpentinites. This assumption was supported by meta-analysis of publicly available Dethiobacterial metagenomes, as well as by the enrichment of a novel phylotype from a deep subsurface non-serpentinizing slightly alkaline water after its amendment with an Fe(III) mineral. Genome analysis of D. alkaliphilus strains revealed that the most probable determinants of iron and sulfur redox transformations in the organism are multiheme c-type cytochromes. Their phylogeny reconstruction showed that sulfur and thiosulfate respiration is most probably provided by evolutionary early forms of unconventional octaheme tetrathionate and sulfite reductases sharing a root with structurally similar group of OmhA/OcwA Fe(III)-reductases. Large sets of other multihemes are likely to provide Fe(III) reduction in both strains. Also, several different, yet phylogenetically related, determinants of anaerobic Fe(II) oxidation were identified in Z-1002 genome, and the oxidation process was further experimentally proven. Considering these results and phylogenetic relatedness of D. alkaliphilus’s sulfur reductases with Fe(III) reducing cytochromes, but not with archetypal bacterial sulfur/thiosulfate reductases, we suggest that sustaining high variation of multiheme cytochromes is an effective adaptive strategy to occupy geochemically contrasting alkaline anaerobic environments. We further propose that sulfur-enriched soda lakes are secondary habitats for D. alkaliphilus comparing to Fe-rich serpentinites, and discuss the evolutionary traits which might occur in prokaryotes on a crucial junction of the biosphere’s history, when intensification of the sulfur cycle outweighed the global significance of the iron cycle.