Microbes sensitive to the cold?

Cold is often used to kill unwanted bacteria in the laboratory under controlled conditions. But what happens under the varying temperatures found in natural environments? What is the impact of Québec's freeze-thaw cycle on microorganism behaviour? For example, can we count on the cold to restrict bacteria mobility following manure spreading near a source of drinking water?

The scientist hopes that her work will lead to improved environmental protection regulations.

Nathalie Tufenkji, a research professor in the Department of Chemical Engineering at McGill University, is at the head of the first scientific team to look into these questions. The answers found thus far are extremely interesting: the freeze-thaw cycle appears to reduce the mobility of certain bacteria and affect their survival, but increases their virulence.

Along with collaborators Subhasis Ghoshal from McGill University, Éric Déziel and Pierre Payment from INRS-Institut Armand-Frappier, and Sarah Dorner from École Polytechnique de Montréal, Nathalie Tufenkji is carrying out her research at McGill's Macdonald Campus Farm and in the laboratory. The study focuses on Yersinia, E. coli and Salmonella. All of these unpleasant bacilli are found in the fecal matter of animals –and therefore in manure–, and can cause serious gastrointestinal problems in humans.

For the purposes of the study, Professor Tufenkji observed the response of the bacteria in a cold chamber under variable temperatures designed to simulate the fluctuating conditions found in nature. She then intends to measure their natural variability in the field after each winter cycle. Ultimately, the scientist hopes that her work will lead to improved environmental protection regulations, which do not always take into account the effect of temperature on microorganism behaviour.

However, before making recommendations for regulatory changes, Nathalie Tufenkji and her team will carry out further virulence testing to determine whether their findings reflect a general behaviour shared by all bacteria, or whether the behaviour is specific to certain species.