Iron and sulfate reduction structure microbial communities in (sub-)Antarctic sediments

Area of Science:

• * Marine microbial ecology
• * Geochemistry
• * Biogeochemical cycling

Background:

• * Cold marine sediments are affected by increased iron input from glacial melt.
• * The impact of these environmental changes on microbial communities is not well understood.
• * Geochemical parameters influencing microbial composition in anoxic sediments require investigation.

Purpose of the Study:

• * To investigate geochemical parameters shaping microbial communities in Southern Ocean sediments.
• * To understand the roles of iron and sulfate reduction in these environments.
• * To identify microbial groups involved in dissimilatory iron reduction.

Main Methods:

• * Analysis of geochemical parameters in anoxic surface sediments from four sites.
• * Microbial community composition analysis using 16S rRNA gene sequencing.
• * RNA stable isotope probing to assess microbial activity and metabolic capabilities.

Main Results:

• * Distinct microbial communities correlated with prevailing sulfate or iron reduction at different sites.
• * The Sva1033 family, previously unrecognized for iron reduction, was abundant and active.
• * Sulfate reducers were active during iron reduction, suggesting cryptic sulfur cycling.

Conclusions:

• * Iron and sulfate reduction are key processes shaping microbial communities in cold marine sediments.
• * The Sva1033 family is identified as a significant dissimilatory iron reducer in these sediments.
• * Cryptic sulfur cycling may mask concurrent sulfate reduction activity.