Trait-based meta-analysis of microbial guilds in the iron redox cycle

Area of Science:

• Microbial Ecology
• Biogeochemistry
• Genomics

Background:

• Microbial iron (Fe) redox cycling is crucial for global biogeochemical processes, nutrient turnover, and contaminant mobility.
• Understanding the functional diversity, ecological roles, and trait architectures of iron-transforming microbes is essential but poorly synthesized across environments.

Purpose of the Study:

• To systematically review and meta-analyze microbial iron redox cycling taxa using a trait-based guild framework.
• To define ecologically coherent microbial iron redox cycle guilds based on phenotypic, genomic, and environmental data.
• To advance predictive microbial ecology by linking metabolic traits with environmental gradients.

Main Methods:

• A systematic review and trait-based meta-analysis of 387 microbial taxa from 314 studies spanning 76 years.
• Integration of phenotypic, genomic, and environmental data to define functional guilds (Fe(III) reducers, Fe(II) oxidizers, dual-capacity Fe oxidizers/reducers).
• Hierarchical clustering and kernel density analyses of ecophysiological traits to identify niche partitioning along environmental filters (pH, iron availability, salinity, temperature).

Main Results:

• Iron-cycling capacities transcend phylogenetic boundaries, with guilds converging in chemically stratified environments.
• Dual-capacity Fe oxidizers/reducers are key mediators of 'cryptic' iron cycling, toggling between oxidative and reductive modes.
• Niche partitioning is evident along key environmental gradients, highlighting distinct habitat preferences for different guilds.

Conclusions:

• The study introduces the Guild Exploitation Pattern, a conceptual lens for understanding iron microbiome assembly.
• The trait-based guild framework provides a data-driven foundation for predicting microbial contributions to iron cycling under changing environmental conditions.
• Highlights the need for functional trait surveys to complement metagenomics and cultivation efforts, especially for understudied dual-capacity species.