Adaptation of Bacillus cereus, an ubiquitous worldwide-distributed foodborne pathogen, to a changing environment

Consequences of climate change on the ecology of pathogens are difficult to forecast. However changes affecting microorganisms will likely involve already known evolution or adaptation mechanisms. Bacillus cereus is a frequent cause of foodborne poisonings and is known as a soil borne bacterium. B. cereus may represent an interesting model to study the impact of climate change on foodborne pathogens. The B. cereus group (or B. cereus sensu lato) displays a wide diversity of strains recently distributed in seven major phylogenetic groups. B. cereus growth domains range from psychrotrophic to nearly thermophilic. Current climate selects B. cereus distribution: psychrotrophes are more common in cold areas, while mesophiles prevail in tropical soils. In response to external signals, B. cereus may adapt to changing environments by varied mechanisms. Some illustrations of the signal transduction systems (two-component systems, alternative σ factors) and of the mechanisms of B. cereus adaptation to major environmental factors (temperature, carbon source, redox potential and pH) are proposed. The environment of sporulation has an impact on spore properties; heat resistance is positively correlated with sporulation temperature. Surveillance needed to detect changes in the epidemiology of B. cereus foodborne poisonings as a consequence of climate change is discussed.