(295c) 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.