Microbial community composition along a 50 000-year lacustrine sediment sequence

Area of Science:

• Microbiology
• Geomicrobiology
• Paleolimnology

Background:

• Subseafloor sediment microbial communities are extensively studied, but deep lacustrine sediments remain undercharacterized.
• Understanding lacustrine microbial diversity enhances knowledge of subsurface biosphere formation under varying environmental pressures.
• Lacustrine sediments provide unique archives for studying microbial life evolution in freshwater environments.

Purpose of the Study:

• To characterize the taxonomic composition of microbial communities in deep lacustrine sediments.
• To investigate the influence of past environmental and geochemical changes on microbial populations over 50,000 years.
• To compare lacustrine subsurface microbial communities with those in marine sediments.

Main Methods:

• High-throughput sequencing of 16S rRNA genes.
• Analysis across high-resolution climate intervals spanning the last 50,000 years.
• Correlation of microbial community shifts with paleoenvironmental and geochemical data.

Main Results:

• Microbial communities in Holocene sediments exhibited highest diversity, influenced by electron acceptor availability.
• Salinity, organic matter, and depositional conditions during the Last Glacial-interglacial cycle acted as selective pressures on deep lacustrine microbial assemblages.
• A genetically distinct deep biosphere emerged, dominated by groups other than surface-prevalent Bathyarchaeota and Atribacteria, though some shallow taxa persisted.
• Deep subsurface community establishment was driven by paleoenvironmental factors, substrate availability, depletion, and organic matter reworking.

Conclusions:

• Past environmental and geochemical dynamics significantly shaped distinct microbial communities in deep lacustrine sediments.
• Lacustrine subsurface biospheres evolve differently from surface communities, influenced by long-term environmental shifts.
• Comparative analysis with marine sediments suggests common principles governing subsurface microbial community development.