BACILLUS-WEIHENSTEPHANENSIS SP. NOV. IS A NEW PSYCHROTOLERANT SPECIESOF THE BACILLUS-CEREUS GROUP

The Bacillus cereus group comprises the four valid species Bacillus ce reus, Bacillus mycoides, Bacillus thuringiensis and Bacillus anthracis . Some isolates of B. cereus are known to be psychrotolerant (growth a t 7 degrees C or below). Here, specific sequence differences are descr ibed between the 16S rDNA, the 23S rDNA, the 16S-23S rDNA spacer regio n and the genes of the major cold-shock protein homologue cspA in a va riety of psychrotolerant and mesophilic B. cereus and B. mycoides stra ins. Randomly amplified polymorphic DNA analysis using three different primers clearly separated psychrotolerant strains of both species fro m the rest of the B, cereus group, as did inverse PCR patterns of the rDNA operons. These data strongly support a hitherto unrecognized fift h sub-group within the B. cereus species group comprising psychrotoler ant, but not mesophilic, B. cereus strains. Despite the latter finding , the DNA sequences investigated exhibited a high degree of sequence s imilarity indicating a close relationship between the species of the B . cereus group. Considering the unusual importance of B. cereus in bot h food poisoning and food spoilage and to avoid merging all species of the group, a new species, Bacillus weihenstephanensis sp. nov., compr ising psychrotolerant 'cereus' strains, is proposed. Isolates of the n ew species grow at 4-7 degrees C but not at 43 degrees C and can be id entified rapidly using rDNA or cspA targeted PCR. The type strain is B . weihenstephanensis WSBC 10204(T) (= DSM 11821(T)).