Master of Science (MSc)
Faculty of Science
Riparian wetlands are unique habitats facilitating all forms of life. The riverbanks of these environments provide ideal conditions for bacteria, plants, and higher organisms. Of particular interest to this research was the variation in microbial community structure at high, intermediate and poor water quality impacted areas. Assessing the capabilities of plants to retain microbial pathogens was identified. Root systems and corresponding soil are ideal locations for bacterial deposition, resulting in attachment at these areas. Biofilm production in these regions is important for long-term establishment, leading to persistence and potential naturalization. Opportunistic pathogens originating from mammalian fecal matter are introduced into these water systems, largely due to anthropogenic impacts. Wastewater treatment facilities, agricultural operations and livestock farming all contributed to determining water quality. This research investigated the levels of Salmonella spp., Enterococcus spp. and Escherichia coli deposition within riparian wetlands. The objectives of this research were to 1) isolate opportunistic pathogens from the environment, 2) assess impacts of contaminant exposure on resistance profiles and how water quality may effect this, 3) compare rhizospheric, rhizoplane and waterborne isolate contaminant response behaviour, 4) assess levels of adhesion mechanism and biofilm production to determine the influence of water quality and isolate source (analyte). The overarching goal of this research project was to best determine the innate capabilities of opportunistic pathogens to be retained in the rhizosphere, rhizoplane and water systems in riparian zones. Additionally, determining their abilities to generate biofilm and successfully grow at varying levels of water quality was investigated.). A range of temperatures (11oC, 28oC, 37oC) were utilized to evaluate the ability of pathogens to synthesize adhesion mechanisms, generate biofilm and resist contaminants. At 11oC, the ability to produce adhesion mechanisms and biofilms during antibiotic exposure was lesser in comparison to warmer temperatures. At 28oC and 37oC, a threshold was reached resulting in synthesis of curli, cellulose and extra polymeric substances as well as increased biofilm formation. Pathogens isolated from rhizospheric soil and root samples were best able to generate biofilms and adapt to contaminant stressors. Resistance profiles were more robust at high temperatures, as 80% of isolates weresusceptible to most antibiotics 11oC, while 70% of isolates resisted 7 or more antibiotics at 28oC and 37oC. Ciprofloxacin, amoxicillin and clavulanic acid, chloramphenicol and ceftazidime resulted in 70% susceptibility whereas vancomycin, tetracycline, linezolid and doxycycline were resisted by 85% of isolates. Under dynamic growth conditions, Enterococcus faecalis acclimated to 1 mM - 0.05 mM of copper and chloramphenicol, however, was inhibited by 0.05 mM - 0.0125 mM of silver. Further, E. faecalis isolated from high water quality sites were more efficient biofilm producers at 28oC under dynamic conditions. This research suggests that although water quality influences microbial behaviour, temperature and varying plant communities at riparian areas may be better parameters to utilize when measuring microbial pathogen retention in the environment.
Coristine, Aaron, "Relationships Between Factors Influencing Biofilm Formation and Pathogen Retention in Complex Rhizosphere Microbial Communities" (2018). Theses and Dissertations (Comprehensive). 2030.
Available for download on Tuesday, March 26, 2019
Environmental Microbiology and Microbial Ecology Commons, Food Microbiology Commons, Immunology of Infectious Disease Commons, Integrative Biology Commons, Microbial Physiology Commons, Molecular Biology Commons, Pathogenic Microbiology Commons, Terrestrial and Aquatic Ecology Commons