Christopher Yost


Phone: 306-585-5223 or 306-585-4285(lab)
Fax: 306-337-2410

Research interests
Host-Microbe Interactions

My lab has two research focuses within the general areas of Environmental Microbiology and Bacterial Genetics

Indicators of fecal pollution in agricultural ecosystems:
Persistence and identification of appropriate pathogen indicators

Deterioration to the health of the environment and ecosystems can have serious consequences for human health. The World Health Organization estimates that water-related illness results in 3.4 million deaths globally per year (Medema et al., 2003), placing waterborne illness as one of the world's most urgent health issues. The burden of waterborne illness affects both developing and developed nations. Water-borne illness remains a significant threat to the health of Canadians, and in particular to those residing in rural regions. Nationally, gastroenteritis from verotoxigenic E. coli, Salmonella, and Campylobacter are estimated to occur as high as 3.3, 6.9, and 19.3 per 1000 population, respectively (Thomas et al., 2006). Increasing demands on agriculture production (ie intensive livestock operations), changes to fertilizer practices, and climate change are all forecast to negatively impact water quality in Canada. To prevent future Walkerton and North Battleford-like outbreaks we must minimize fecal contamination of water sources and better understand the pathogenic risks associated with fecal contamination. Therefore new approaches are urgently needed to quantify specific sources of fecal contamination and accurately predict the human health risks associated with these sources of fecal pollution. The outcomes of the proposed research will help guide policy decisions for measuring risks of pathogen infection associated with fecal pollution as well as provide critical data required for implementing the most effective policies for mitigation of fecal contamination in agriculturally influenced watersheds.

Characterizing the function of the cell envelope in rhizobia

The biological fixation of atmospheric nitrogen is a critical component to the global nitrogen cycle and is particularly valuable to worldwide agriculture. Globally, nitrogen fixation symbioses between rhizobia and legumes are the major source of nitrogen input to agricultural systems, and many legume species, such as peas, lentils, soybeans and chickpeas are important food crops. Rhizobial-legume interactions have been studied extensively, but the process is complex and further fundamental research is required to appreciate this complexity fully. Rhizobia induce the formation of root nodules on legume plants, and within these nodules, the bacteria convert atmospheric nitrogen to a form that is useable by the plants. Rhizobia must survive both in the soil environment and within a host plant. The cell envelope is important in both instances; it plays a critical role as a protective barrier against toxins and stressors and is also the initial point of contact between the bacterial cell and host cell during invasion. The long-term objectives of my research program are to use genetics based methodologies to discover unknown regulatory pathways that control cell envelope development in rhizobia and to identify novel genes required for proper cell envelope development. Results from this research may be applied to other bacterial-host relationships, particularly pathogenic interactions within the alpha-proteobacteria class, possibly to identify novel mechanisms that regulate the pathogenic process.