Metabolic potential of microbial communities from ferruginous sediments

Area of Science:

• Geomicrobiology
• Biogeochemistry
• Environmental Science

Background:

• Ferruginous (iron-rich, sulfate-poor) conditions were common in Earth's early oceans but are rare today.
• Lake Towuti, Indonesia, provides a modern analogue for ancient ferruginous environments.
• The microbial metabolism and biogeochemical cycling in these settings are poorly understood.

Purpose of the Study:

• To investigate the metabolic potential of microbial communities in ferruginous sediments.
• To link microbial metabolism to geochemical processes, specifically iron, sulfur, and carbon cycling.
• To understand microbial roles in environments analogous to the Archean ocean.

Main Methods:

• Geochemical measurements including pore water chemistry and sulfate reduction rates.
• Metagenomic analysis to identify microbial genes and metabolic pathways.
• Analysis of sediment cores up to 50 cm depth.

Main Results:

• Microbial diversity and genes for sulfate reduction (dsrAB) and methanogenesis (mcrA) decreased with sediment depth.
• Potential for iron and sulfate reduction was inferred from microbial taxa present.
• Acetate concentrations indicated active fermentation, supporting respiration and methanogenesis.
• Evidence for anaerobic methane oxidation was found.

Conclusions:

• Microbial metabolism in anoxic ferruginous sediments facilitates coupled iron, sulfur, and carbon biogeochemical cycling.
• Lake Towuti's microbial communities offer insights into early Earth biogeochemical processes.
• Fermentation, sulfate reduction, and methanogenesis are key processes in these environments.