This project will continue to develop a new means to study biological energy transduction in situ. By conducting the proposed spectroscopic studies under noninvasive physiological conditions, we will exploit new and powerful approaches to examine the extents and rates of biochemical events without disrupting the complexity of the live cellular environment. This new technology can be applied to any biological problem of interest to the DOE. In our efforts to explore the capabilities of these new methods, we will quantitatively examine the dynamic behavior of the electron transport system at the microbe-mineral interface, an interaction that has heretofore been difficult to probe directly. Thus, this project will address the DOE's desire to understand the functional microbial processes that link the internal metabolic processes of each species to its external biogeochemical activities. Our focus on oxidative respiration by acidophilic organisms will complement the DOE's impressive portfolio on neutrophilic bacteria that electrochemically reduce iron, uranium, sulfur, and other redox-active metals and metalloids. It is evident that a complete understanding of the biogeochemistry of redox-active elements of interest to the DOE/BER must include fundamental information on both reductive and oxidative processes.
The proposed collaboration with the proteomics capabilities of the EMSL will enable us to identify the different proteins expressed into the respiratory chains in each organism. The anticipated outcome of each ex situ proteomic analysis will be the identification of the principal electron transfer proteins and pathways in each unique microorganism that conducts respiration on extracellular iron. The participation of the EMSL is crucial to achieving our research objectives. Xavier University is a small HBCU with limited infrastructural and instrumental capabilities for the types of services and expertise that the EMSL can offer. This is an extraordinary opportunity for collaboration with experienced personnel at a well-equipped national laboratory.
We note that environmental samples taken from acid drainage/hard-rock mining sites and the contents of biohydrometallurgical tanks share many of the characteristics of the microbial communities that we propose to study herein: such samples are frequently characterized by a limiting number of principal microorganisms at any instant (3 to 7); they always contain a mixture of autotrophs, mixotrophs, and heterotrophs; their primary energy metabolism comes from aerobic respiration on inorganic substrates; the bulk of their reduced carbon comes from the CO2-fixation activities of the community; and they are subject to periodic changes in pH, temperature, and types of energy substrates. Consequently, we expect the complexities of the microbial communities that we assemble to mimic the complexities of those found in the relevant environments. But we also expect each model community to be sufficiently simple so as to be tractable to the systems biology studies as we have defined them herein. We posit that these model systems will permit us to identify functions and behaviors in the intact systems that are not plausibly predicted from those of the simple sums of the component parts.