The impact of a horizontally acquired genetic material on the transcriptional landscape and phenotypic behaviour of Bacillus cereus as a model to unde

Bacillus cereus strains are ubiquitous in the environment by virtue of their widespread invertebrate associations. Conversely B. anthracis is comparatively rare as it is genetically "locked" into an exclusively mammalian pathogenic life cycle. We are investigating the B. cereus strain G9241 (BcG9241), which exhibits phenotypes normally associated with B. cereus at ambient temperatures, yet is capable of causing an anthrax-like illness in people. Therefore, the concern is that strains such as BcG9241 may have the potential to be prevalent in the environment, acting much like their B. cereus ancestors, until they enter a mammalian host, whereupon they can cause anthrax-like disease. Our preliminary work has confirmed that this switch in pathogenic potential is dictated by temperature, with exposure to 37 degrees C suppressing many of the B. cereus phenotypes, leading to a B. anthracis like state. We have shown that this regulatory switch operates at the post-transcriptional level by an as yet unknown mechanism. We argue it is important to understand how readily this mechanism evolved, for estimating the current prevalence and predict future likelihood of other BcG9241-like strains becoming a threat. Indeed, there have been increasing reports of isolates of similar strains from around the world, including the B. cereus biovar anthracis strains. Furthermore, we argue that the current push for industrial scale farming of insects as "food or feed" has the potential risk of creating unintentional "anthrax factories", should a BcG9241-like crossover strain gain access to the resident insect population. It is therefore important to better understand how such strains can achieve this pathogenic switch.