EAGER: Development of Multi-Population 13C Isotopic Analyses for Elucidating Intra-Cellular Metabolic Responses within Mixed Populations of Nitrifying Bacteria

Oregon State University, Corvallis OR

Investigators

Abstract

1239870/ Chaplen This EAGER award funded by the Biotechnology, Biochemical and Biomass Engineering Program at the National Science Foundation aims to develop tools to examine nitrogen cycling in microbial communities containing nitrifying bacteria. Metabolic flux analysis models are used to postulate the distribution of metabolic fluxes in cells based on experimental measurements of external fluxes. These models have the potential for being highly useful because they can predict biochemical production capabilities, and metabolic yields, including metabolic carbon efficiency, metabolic energy efficiency, and the balance between biomass production and metabolite overproduction. A key approach to increasing the utility of MFA is the use of stable isotopic tracers, usually 13C labeled, to provide information regarding intracellular flux distributions as additional constraints in parameterizing the model. Recently, published studies have demonstrated that isotopic tracer data from cellular peptides is homogeneous within a single species. The researchers hypothesize that this work can be extended such that species specific isotopic tracer MFA can be used to identify nitrogen cycling within microbial communities of nitrofying bacteria. The major goal of the proposed research to extend these advances to characterize microbial communities using mixed cultures of two model chemolithoautotrophic nitrifying bacteria: Nitrosomonas europaea and Nitrobacter hamburgensis. Nitrifying bacteria are key elements of the N cycle for controlling movement of inorganic N. As an ammonia-oxidizing bacterium, N. europaea extracts energy for growth solely from the oxidation of ammonia (NH3) to nitrite (NO2-). The waste product of N. europaea, NO2-, is the growth substrate of the nitrite-oxidizing bacterium N. hamburgensis, which extracts energy for growth from the oxidation of NO2- to NO3-. The overall system dynamics of coupled microbiological/ physical/chemical systems in the soil and elsewhere may be an important factor in elucidating the biogeochemical impact of global environmental change engendered by humankind. Understanding nitrogen transformation in unmanaged ecosystems, in wastewater treatment, and control of nitrification rates in soils amended with ammonia-based fertilizers, requires a thorough knowledge of the interaction of these organisms with each other and the environment. This research is highly integrative drawing on engineering and scientific knowledge and expertise from biological engineering, metabolic modeling, microbiology, and systems biology and will provide excellent training opportunities for the undergraduates and high-school students and K-12 teachers involved through outreach activities. The outreach activities proposed as part of this research will increase the awareness of the K-12, general public and scientific communities in systems biology, microbiology and the metabolic modeling. Finally, the Co-PIs have a demonstrated commitment to recruiting and mentoring minorities and underrepresented groups and will continue to make this a high priority for this project.