Bacillus cereus F0837/76

Bacteria of the group cereus are ubiquitous and usually isolated from soil. However, these microorganisms are the real predators and from time-to-time can be isolated from dead insects or even animals, those deaths they were the cause.
Bacillus cereus is an acronym for the large group of bacteria which includes B. thuringiensis (insect killer), B. anthracis (animal killer), B. weihenstephanensis (able to grow in cold soil), B. mycoides (forming filaments). If no one of the above properties is detected, the Bacillus of this group is usually labeled by a neutral name B. cereus.
The bacteria of this group is now attracting increasing interest of researchers working on bacilli and other gram-positive bacteria. One of the fundamental and practical questions is how the ecological adaptation of these bacteria produces lines pathogenic for animals and insects (like B. anthracis or some B. thuringiensis lines). Intensive phylogenetic studies revealed the epidemic structure of this bacterial population. Some strains of B. cereus are non-hazardous (such strains are used as animal probiotics), other strains caused food poisoning, either emetic or diarrheic.

Most of emetic strains, as well as B. anthracis, seem to represent a single clone, but the diarrheic strains cannot be easily discriminated. It is very important to understand the genetic differences between the strains pathogens and non-pathogens, and also mechanisms by which they can evolve from the latter to the first.

Several years ago genome mapping studies of this bacterial group revealed that a potential mechanism of its short time evolution could be genome shuffling between large plasmids, temperate phages and the most mobile parts of the chromosome situated somewhere between 1,000 and 4,000 kb.
Analysis of available genomes indicated also that this part of the chromosome is the most divergent between different strains. The strain F0837/76 possesses the smallest “stable” chromosome and is closely related to B. anthracis. Moreover it is able to synthesize toxins involved in diarrheic symptoms in significant amounts. Genomic studies of this strain, notably its detailed comparison to B. anthracis, should unveil the subtle features of genome organization that are related to pathogen emergence.
Gathering such data will certainly inspire new ideas about the short time evolution of these bacteria, which should allow scientists to predict, and if necessary to stop, its potential pathogenic emergence.