By design: The architecture of microbial redox cycling

The authors’ work on mine systems, combines field and laboratory integrated microbial geochemical investigation with high-resolution techniques enabling characterization and visualization at the bacterium scale (i.e. STXM). The results indicate a repeated motif of socially organized microbial cooperation occurring within microbial consortial macrostructures (pods). The pod structure directly enables the specific geochemical processes linked to the metabolic function of the consortial members. These microbially linked geochemical processes have important ramifications for bulk system geochemistry that were previously unknown. Results from two examples: (1) microbial metal interactions within AMD biofilms and (2) sulfur redox cycling by a novel consortia within mine waters, illustrate how the ecology of the pod consortia is linked to pod biogeochemical macrostructure as well as to the resulting geochemistry associated with pod metabolism. In both instances the pod structures enabled the associated consortia to carry out reactions not predicted by classic geochemical understanding of these systems. Investigation of AMD biofilm biogeochemical architecture capturing the micro-scale linkages amongst geochemical gradients, metal dynamics and depth resolved micro-organism community structure, illustrated a novel biomineralization process driven by biofilm associated pods controlling biofilm metal capture. Similarly, the groups’ recent discovery of an environmental S redox cycling, pod-forming, consortium revealed ecologically driven S cycling with previously unknown implications for both AMD mitigation and AMD carbon flux modeling. These results highlight how microbes cooperatively orchestrate their geochemical environment, underscoring the need to consider syntrophic community activity in environmental processes and the requirement for integrated, high-resolution techniques spanning geochemistry, molecular microbiology and imaging to reveal the biogeochemistry involved.