Contaminant stress on ecosystems: investigating microbial redox transformations of metal(loids) and novel tracers

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Interactions between minerals and microorganisms are of fundamental and growing interest due to their influence on the transport and toxicity of dissolved metal and metalloid ions in water-rock systems and their control on weathering and formation of minerals. The microbial processes that regulate the mass transport, transformations, and toxicity of metals in the environment are complex. Metals and metalloids can be enzymatically or non-enzymatically concentrated and dispersed by microbes in their environment. For example, studies in our lab have shown that metal/loids formed in the presence of bacteria can undergo dramatic transformation and speciation in changing redox environments. These differences of course, can depend on the bacterial species present, promoting template effects due to differences in cell wall structure between species. Even in single species, variations can result in metabolic state or the concentration and type of exudates (extracellular polymeric substance, EPS) produced during growth can affect the properties of the bio-minerals and thereby potentially influence their adsorptive capacity within the surrounding media. This research program will focus on key mineral systems (e.g. iron sulphate analogues such a jarosite end member minerals) influenced by reducing and oxidizing forms of bacteria. Experiments will use pure cultures and microbial consortia (isolated from iron reducing zones in sediments and soils). Natural iron sulphates including those formed in acid sulphate soil systems and synthesized end-members will be used in controlled laboratory experiments. In addition research within this program will also focus on developing new environmental tracers to characterize anthropogenic influences. Maintaining sustainable freshwater resources are directly tied to Canada's continued socio-economic success (i.e. agriculture, industry, people, and tourism). The minerals and energy industries in Canada are in the midst of their greatest expansion in the last three decades. This research program will enhance our understanding of how bacteria control metal release in natural ecosystems as well as those impacted by mining sector and anthropogenic inputs.