The Distribution of Acidophilic Iron Oxidizers is Consistent with Environmental Filtering, Dispersal Limitation, and Competition.

Acid mine drainage (AMD) is a global pollution problem characterized by low pH and high concentrations of metals. Active remediation is often cost-prohibitive, but Fe(II)-oxidizing microbes may be used for passive bioremediation. To leverage these species, we must understand the factors that control their distribution. Here, we examined the environmental and ecological factors that control these species with the aim of determining if microbial seeding is a viable remediation strategy. Although stochastic processes appeared to control the distribution of the majority of taxa inhabiting AMD ecosystems, the distribution of Fe(II) oxidizers appeared to be driven by environmental filtering and competition. The abundance of all the major Fe(II)-oxidizing genera had significant relationships with pH, with pH explaining 10%-38% of the variation in their abundance. The genera appeared to have pH preferences, with Acidithiobacillus and Leptospirillum preferring environments with pH below 3, Gallionella, Sideroxydans, and Ferritrophicum preferring environments with pH above 3.5, and Ferrovum preferring intermediate-pH environments. Once the effect of pH is removed, genera that share pH preferences were negatively correlated, indicating that they were likely competing for the Fe(II)-oxidizing niche in their preferred environments. Communities were also shaped by dispersal limitation, which suggests that microbial seeding may be possible in these environments. Future seeding attempts should consider species interactions and ecology more generally to inform their efforts. IMPORTANCE:Acid mine drainage (AMD) is a global pollution problem affecting streams worldwide. One method of remediating AMD is by using naturally occurring microbial communities to remove iron and other metals. However, we do not have a complete understanding of the factors that control the distribution of these species or if it is possible to seed species from one environment into another. Here, we examine the factors that control community assembly in AMD ecosystems. We find that individual species appear to be dispersal-limited; thus, microbial seeding may be a viable method for AMD remediation.