Linking Microbial Community Structure to Function in Representative Simulated Systems

Abstract

Pathogenic bacteria are generally studied as a single strain under ideal growing conditions, although these conditions are not the norm in the environments in which pathogens typically proliferate. In this investigation, a representative microbial community along with Escherichia coli O157:H7, a model pathogen, was studied in three environments in which such a pathogen could be found: a human colon, a septic tank, and groundwater. Each of these systems was built in the lab in order to retain the physical/ chemical and microbial complexity of the environments while maintaining control of the feed into the models. The microbial community in the colon was found to have a high percentage of bacteriodetes and firmicutes, while the septic tank and groundwater systems were composed mostly of proteobacteria. The introduction of E. coli O157:H7 into the simulated systems elicited a shift in the structures and phenotypic cell characteristics of the microbial communities. The fate and transport of the microbial community with E. coli O157:H7 were found to be significantly different from those of E. coli O157:H7 studied as a single isolate, suggesting that the behavior of the organism in the environment was different from that previously conceived. The findings in this study clearly suggest that to gain insight into the fate of pathogens, cells should be grown and analyzed under conditions simulating those of the environment in which the pathogens are present.

Effects of copper particles on a model septic system's function and microbial community

“…The septic system used for these experiments was developed and reported on previously (Marcus et al, 2013). The model septic tank was designed to have a typical residence time of three weeks in the primary compartment (Marcus et al, 2013 and EPA, 2002).…”

“…The model septic tank was designed to have a typical residence time of three weeks in the primary compartment (Marcus et al, 2013 and EPA, 2002). The system used here mimics a full-scale septic system because it represents a scaled down two-chambered system with the correct 2:1 ratio for the chamber volumes, uses synthetic greywater representing household waste, and contains “toilet waste” which is simulated by adding fecal bacteria from a model human colon reactor.…”

“…S1). Briefly, the influent added to the septic tank is composed of three components: deionized water (DI H 2 O), synthetic greywater, and colon waste (Marcus et al, 2013). The composition of the colon waste and synthetic greywater is listed in the SI.…”

“…Three individual experiments (one experiment per Cu particle) were conducted in the system and consisted of: four weeks of baseline (no Cu) and three weeks of Cu addition (total of 1500 mg added and denoted as Cu weeks 1-3) which were followed by three weeks where Cu was no longer added to the system (denoted as post-Cu weeks 1-3). The model septic tank was designed to have a typical residence time of three weeks in the primary compartment (Marcus et al, 2013 and EPA, 2002). The purpose of the three weeks of analysis after the Cu addition (post-Cu weeks 1-3) was to determine if the effluent quality would return to values recorded during the baseline period.…”

“…Microbial community phenotype can be affected by perturbances in aquatic systems (Marcus et al, 2013). Therefore, because septic system function is linked directly to metabolic activity of the microbial community, changes occurring to the community phenotype were also measured.…”