Acidic pit lakes: Novel biogeochemical reactors evaluated via multi-omics approaches

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Acid mine drainage is globally among the most widespread and expensive forms of pollution.This project will investigate how to use sunlight and natural microbial communities to providecost-effective remediation of pollution caused by mining (acid mine drainage), thus improvingaccess to clean water for humans and the ecosystems that support them. In addition, theproject will contribute more broadly to the development of methods and new understanding ofhow microbial populations interact with minerals, organic compounds, and other microbialpopulations in the environment. This understanding is crucial in order to harness the enormousbiotechnological potential of microbial systems that can be engineered to provide essentialservices to human societies. The proposed work will improve environmental health, increasediversity in the STEM pipeline, and strengthen international scientific collaborations. Womenand underrepresented graduate and undergraduate students will be recruited to work on thisproject. This project will promote collaboration between U.S. and international researchers bybuilding on long-term relationships between the Spanish Geological Survey (IGME) and PennState, such that participants will benefit from international science and engineering training.The goal of this project is to identify strategies to stimulate sulfide production in acidic pit lakes.As a model system, we selected the anoxic deep layer of Cueva de la Mora (CM), a permanentlystratified acidic pit lake in SW Spain that is among the most intensively studied in the world.Two competing hypotheses emerged from our previous research: 1) Sulfide production islimited by organic carbon, or 2) Sulfide production is limited by zero-valent sulfur. The projectobjectives are to: A) Stimulate autotrophic and heterotrophic sulfide production in laboratoryincubations inoculated with the CM anoxic layer microbial community; B) Resolve the metabolicpotentials and activities of the active populations in the stimulated communities; and C)Identify interactions between microbial populations cycling C, S, Fe, N, and P under sulfide producingconditions. Tasks to address these aims include: 1) Conduct a field campaign tocollect large quantities of biomass from the anoxic layer of CM; 2) Conduct laboratoryincubations to evaluate sulfide production under different conditions; 3) Sequencemetagenomes and metatranscriptomes to identify the most abundant and active microbialpopulations; and 4) Construct conceptual species-level and community-level metabolic modelsto generate new hypotheses about how to increase sulfide production and thereforebioremediation potential. This project will contribute to a fundamental and mechanistic understanding of howmicroorganisms interact to produce and consume sulfide in acidic environments, which iscrucial to mitigating the toxic effects of acid mine drainage. The results will advance knowledgeof previously undescribed and novel microbial species, including details of their metabolicpotentials, enzymatic machinery, and evolutionary relationships. There are currently only 1-2sulfide-producing isolates able to grow at pH4, although the diversity of this group is probablyhigher and remains undescribed. Microbial communities in nature are made up of mutuallydependent populations that exchange metabolites, yet scientific studies rarely consider thiscomplexity explicitly. A significant merit of this proposal is that it focuses on a naturalenvironment with intermediate complexity, appropriate for expanding and adapting modelingtools developed for laboratory cultures for natural ecosystems. Documenting microbialinteractions in communities is key to understanding community assembly and to harnessing theenormous biotechnological potential of engineered microbial systems that can provideessential services to human societies.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.