Functional redundancy imparts process stability to acidic Fe(II)-oxidizing microbial reactors

Area of Science:

• Microbial Ecology
• Biogeochemistry
• Environmental Microbiology

Background:

• Lab-scale reactors studying microbial iron(II) oxidation at low pH showed stable rates across varying conditions.
• The stirred reactor environment, which minimizes natural spatial and temporal variations, surprisingly supported diverse microbial communities.

Purpose of the Study:

• Investigate the reasons behind the co-existence of multiple autotrophic iron(II)-oxidizing taxa in controlled reactor environments.
• Determine the metabolic potential differences among co-existing taxa regarding iron oxidation, carbon fixation, nutrient acquisition, and biofilm formation.

Main Methods:

• Utilized metagenomic analyses to assess the metabolic capabilities of microbial communities within the reactors.
• Examined differences in pathways for iron(II) oxidation and carbon fixation.
• Investigated substrate acquisition strategies and biofilm formation potential.

Main Results:

• Metagenomic analysis revealed distinct metabolic potentials among co-existing iron(II)-oxidizing taxa.
• Differences were observed in iron oxidation pathways, carbon fixation, nutrient acquisition, and biofilm formation.
• Biofilms were found to create distinct geochemical niches, enabling co-existence.

Conclusions:

• Distinct metabolic potentials drive the long-term co-existence of multiple autotrophic iron(II)-oxidizing populations by enabling differential growth on limiting resources (N, P, O2).
• Biofilms play a critical role in establishing micro-niches that facilitate the co-existence of diverse taxa within the same apparent metabolic niche.
• Functional redundancy across co-existing taxa contributes to the overall stability of microbial processes in these reactors.