Bacillus cereus is a Gram-positive,

Bacillus cereus is a Gram-positive, aerobic-to-facultative,spore-forming rod widely distributed environmentally and bearinga close phenotypic and genetic (16S rRNA) relationships to several other Bacillus species, especially B. anthracis .
The bacterium exists as a spore former and vegetative cell innature and as a vegetative cell when colonizing the human body.
Transmission electron microscopy ofthe vegetative cell reveals a cytoplasmic membrane surroundingthe cellular content . In addition, some strains containan outermost crystalline surface protein (S layer). The core of the spore is surrounded by the inner membrane, cortex,and inner and outer coats.
While devoid of metabolic activity,the B. cereus spore is refractory to extreme environmental conditionsinclusive of heat, freezing, drying, and radiation and may beregarded as the infective agent for this bacterium. In keeping with its close relationship to B. anthracis , thesurface antigens of the spore share epitopes with B. anthracis spores as determined serologically by cross-agglutination.
In the food industry the spores of B. cereus are particularlytroublesome because spores can be refractory to pasteurizationand gamma radiation, and their hydrophobic nature allows themto adhere to surfaces.