Metabolic diversity of the Ferrovales and potential contributions to iron oxidation

Active and abandoned metal and coal mines generate acidic, metal-laden water that pollutes downstream areas, commonly referred to as acid mine drainage (AMD). AMD is host to microbial communities, including acidophilic iron oxidizers. Microbially-mediated iron oxidation is a desirable (bio)remediation strategy for AMD. Ferrovales are a common Fe-oxidizing bacterial group observed in AMD globally and thus could be an exceptional target for bioremediation strategies. However, Ferrovales are difficult to culture and both phylogenetically and metabolically diverse. To better understand the potential for Ferrovales to contribute to AMD bioremediation, we circumvented limitations in culture-based approaches and analyzed 240 genomes and metagenome assembled genomes from the Ferrovales, including taxa from AMD sites with high iron oxidation rates. The phylogenetic and physiological diversity of this group was greater than previously known and multiple Ferrovales taxa can co-occur. For example, we observed taxa that varied in mobility (based on the presence or absence of flagellar biosynthesis genes) and taxa that encode multiple iron oxidation pathways. We also identified Ferrovales that are likely capable of anoxygenic photosynthesis. Our data suggest that differences in physiology promote niche differentiation along resource axes and co-occurrence of multiple taxa. It's possible that multiple co-occurring iron oxidizing taxa could support a more robust microbial community, resulting in higher iron oxidation rates and more efficient bioremediation.