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

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 provide cost-effective remediation of pollution caused by mining (acid mine drainage), thus improving access to clean water for humans and the ecosystems that support them. In addition, the

project will contribute more broadly to the development of methods and new understanding of how microbial populations interact with minerals, organic compounds, and other microbial populations in the environment. This understanding is crucial in order to harness the enormous biotechnological potential of microbial systems that can be engineered to provide essential

services to human societies. The proposed work will improve environmental health, increase diversity in the STEM pipeline, and strengthen international scientific collaborations. Women and underrepresented graduate and undergraduate students will be recruited to work on this project. This project will promote collaboration between U.S. and international researchers by

building on long-term relationships between the Spanish Geological Survey (IGME) and Penn State, 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 permanently

stratified 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 is limited by organic carbon, or 2) Sulfide production is limited by zero-valent sulfur. The project objectives are to: A) Stimulate autotrophic and heterotrophic sulfide production in laboratory

incubations inoculated with the CM anoxic layer microbial community; B) Resolve the metabolic potentials 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 producing conditions. Tasks to address these aims include: 1) Conduct a field campaign to

collect large quantities of biomass from the anoxic layer of CM; 2) Conduct laboratory incubations to evaluate sulfide production under different conditions; 3) Sequence metagenomes and metatranscriptomes to identify the most abundant and active microbial populations; and 4) Construct conceptual species-level and community-level metabolic models

to generate new hypotheses about how to increase sulfide production and therefore bioremediation potential. This project will contribute to a fundamental and mechanistic understanding of how microorganisms interact to produce and consume sulfide in acidic environments, which is crucial to mitigating the toxic effects of acid mine drainage. The results will advance knowledge

of previously undescribed and novel microbial species, including details of their metabolic potentials, enzymatic machinery, and evolutionary relationships. There are currently only 1-2 sulfide-producing isolates able to grow at pH