Microbial Community Responses to Contaminants and the Use of Molecular Techniques

Human activities threaten global ecosystems through the introduction of a range of contaminants. The potential effects of contaminants are commonly tested on organisms, or cell lines, in separate tests: one toxicant and one species at a time. The results have limited predictive capacity in complex ecosystems, and when they are used to calculate guideline toxicity values, multiple safety factors must be applied to mitigate this uncertainty. Community responses can provide a more realistic assessment of contaminant effects but may be more difficult to detect and interpret. In recent years, advances in molecular approaches have significantly improved our ability to investigate community responses at the micro scale. Microbial groups represent a major source of biomass and chemical activity in many ecosystems and they include many of the most chemically sensitive organism groups. Traditional microbial ecotoxicological studies have either measured impacts on diversity or on ecosystem function, with very few attempting to quantify both diversity and function at the same time. Molecular approaches to microbial ecotoxicology have the potential to reveal novel elements of ecosystem change such as the mechanisms behind functional responses to contaminants. This is crucial to understand because structural changes do not necessarily translate to a change in function and vice versa. Increasing our understanding of stress-related structural and functional changes in microbial groups that drive global biogeochemical cycles will enable highly relevant and sensitive predictions of the impact of contaminants on ecosystem health.