274555 Linking Microbial Structure to Function in Representative Simulated Biological Systems
Linking Microbial Structure to Function in Representative Simulated Biological Systems
Ian Marcus, PhD Candidate
Professor Sharon L. Walker, Advisor
Chemical and Environmental Engineering, University of California, Riverside
The common paradigm when studying pathogenic microorganisms in the lab has been to grow the cells as a single strain in rich nutrient media and then to harvest and evaluate the organisms' phenotypic and/or genotypic characteristics. However, this traditional approach overlooks a critical fact that these pathogens do not exist in such idealized conditions. Microorganisms survive in complex communities of multiple species of bacteria, archaea, fungi, and protozoa, though bacteria make up most of the biomass. It is therefore imperative to study the microbial community along with the pathogens as a biological system, and to establish the community's effect on the subsequent introduction of these pathogens into the environment. Ultimately with this knowledge, the impact of the host microbial community on the virulence of pathogens in aquatic environments can be identified and the potential environmental health risk assessed.
The overall goal of this investigation is to ascertain the effect the addition of pathogenic E. coli O157:H7 has on the host microbial community through commonly encountered biological systems relevant to water quality. A series of experiments have been used to evaluate the microbial community structure and function in three simulated systems: a colon, septic tank, and groundwater. Pyrosequencing was performed to determine the microorganisms present, extensive physical-chemical analyses on the community of microorganisms and pathogen (i.e. electrophoretic mobility, cell size, surface charge density, hydrophobicity and extracellular polymeric substances) have been performed in each of these systems, as well as transport experiments of the community and pathogen in a macroscopic, packed-bed column system to simulate their behavior once introduced into the environment. The results of this ongoing study will give greater insight into the understanding of the way in which environmental factors influence the fate and transport of pathogenic microorganisms when they enter and are transported in aquatic environments. Work to date has shown that the physical-chemical characteristics and transport of the microbial community change depending on exposure between the model colon and representative aquatic systems. Specifically, the microbial community is more hydrophilic, has more negative electrophoretic mobility, lower surface charge density, a higher quantity of EPS and has lower attachment efficiency when sampled from the model colon, as compared to the representative aquatic systems. With the addition of the model pathogen the hydrophobicity and electrophoretic mobility increases, while other trends remain consistent. The research presented will include comparisons of the fate and transport of the microbial community with the microorganisms present to link the microbial structure to function in synthetic biological systems.