This award is funded under the American Recovery and Reinvestment Act of 2009 (Public Law 111-5).
Soil, sediment and subsurface environments harbor a tremendous diversity of microbes, and a major research goal is to better understand how such complex systems evolve, function, and respond to environmental changes. The reductionist approaches that focused on individual bacterial populations provided a wealth of valuable information, usually under simplified conditions, but to truly understand how complex microbial communities function, the interactions and interdependencies between different populations inhabiting the same environment must be explored. The premise of this proposal is that many bacteria engage in unknown interactions with neighboring organisms, and that these interspecies links can be characterized using microbiological and genome-enabled approaches. Dehalococcoides and free-living, pleomorphic spirochetes (FLiPS) are members of natural river sediment and aquifer microbial communities. Dehalococcoides are highly specialized bacteria that gain energy for growth by removing halogen substituents from many hydrocarbons, including priority pollutants. This process is called organohalide respiration, and as the bacteria breathe halogenated hydrocarbons (just like we breathe air), the contaminants are detoxified. Dehalococcoides bacteria grow very poorly in isolation but perform robustly in mixed cultures when FLiPS are present. Conversely, FLiPS benefit from Dehalococcoides, and a major goal of the project is to explore the biomolecular basis of these microbe-microbe interactions. This project will characterize unexplored microbe-microbe interactions (symbiosis) at the fundamental, molecular level and shed light on the evolutionary mechanisms that lead to beneficial interactions between distinctly different microbial populations. This research project will generate new understanding on how microbe-microbe interactions develop, operate, and persist, while affecting specific functions of the community (e.g., detoxification of halogenated hydrocarbons). This project will not only advance knowledge of Dehalococcoides and spirochete biology, but will further improve our predictive ability how microbial communities function and respond to perturbations. Two doctoral students and three summer undergraduate students from the University of Puerto Rico will engage in this research effort.