Microbial Ecology of Soda Lakes

Soda lakes are hypersaline, high-pH environments enriched in sodium carbonates, creating dual extremes of alkalinity and salinity. They harbour remarkably diverse microbial communities that thrive in conditions hostile to most life. Primary producers such as cyanobacteria and phototrophic Proteobacteria form dense mats, driving high rates of carbon fixation via pathways including the Calvin-Benson-Bassham cycle. Heterotrophs, sulphur oxidisers and reducers, and methanogenic archaea contribute to fully functioning carbon, sulphur and nitrogen cycles. Adaptations include specialised osmoprotectants, pH homeostasis mechanisms and extremozymes that enable enzymatic activity under haloalkaline stress. Metagenomic and cultivation-based studies have revealed novel lineages and functional potentials, including uncultured members of the Candidate Phyla Radiation and previously unrecognised pathways for polyol degradation and aceticlastic methanogenesis. Soda lakes thus serve as model systems for understanding extremophile ecology, biogeochemical processes and hold promise for biotechnological applications such as biocatalysis, sulphur remediation and carbon dioxide conversion.

Research from Nature Portfolio

Analyses of phototrophic mats from geographically distant soda lakes have uncovered a shared core microbiome of fewer than a hundred abundant bacterial taxa, reflecting common selection pressures across continents. Metagenome-assembled genomes and proteomic data demonstrate how phototrophs allocate resources to niche complementarity, with unexpected carbon fixation by phyla such as Gemmatimonadetes alongside Cyanobacteria and Gammaproteobacteria. This work informs strategies to harness microbial communities for biotechnologies that convert carbon dioxide. Complementary studies of an endorheic soda lake revealed the taxonomic diversity of water, sediment and fish-associated microbiota. High-throughput 16S rRNA gene sequencing before and after enrichment showed dominance of Proteobacteria, Firmicutes and Cyanobacteria, highlighting habitat-specific shifts and the influence of pH and salinity on community assembly.

Microbial Ecology of Soda Lakes publication trend

The graph below shows the total number of articles in microbial ecology of soda lakes across all publications each year (not limited to Nature Index journals).

Technical terms

Soda lake: A saline, alkaline lake with elevated concentrations of sodium carbonates and high pH.

Haloalkaline: Characteristic of environments with both high salinity and high pH, requiring specialised adaptations.

Metagenome-assembled genome (MAG): A draft genome reconstructed from environmental DNA sequences without prior cultivation.

Aceticlastic methanogenesis: Methane production by archaea using acetate as the substrate.

Osmoprotectant: A compound synthesised by cells to balance osmotic pressure under saline conditions.

Polyol: A sugar alcohol that can serve as a carbon and energy source in microbial metabolism.

References

1. Phenotypic and genomic characterization of the first alkaliphilic aceticlastic methanogens and proposal of a novel genus Methanocrinis gen.nov. within the family Methanotrichaceae. Frontiers in Microbiology (2023).
2. Halanaerobium polyolivorans sp. nov.—A Novel Halophilic Alkalitolerant Bacterium Capable of Polyol Degradation: Physiological Properties and Genomic Insights. Microorganisms (2023).
3. A metagenomics roadmap to the uncultured genome diversity in hypersaline soda lake sediments. Microbiome (2018).
4. A shared core microbiome in soda lakes separated by large distances. Nature Communications (2019).
5. Microbial community of soda Lake Van as obtained from direct and enriched water, sediment and fish samples. Scientific Reports (2021).