Discrimination of

Bacillus anthracis B. cereus B. anthracis B. cereus B. anthracisB. cereus B. cereus The present invention is directed to a novel method of discriminating a highly infectious bacterium from a group of closely related microorganisms. Sequence variations in the 16S and 23S rRNA of the subgroup including are utilized to construct an array that can detect these sequence variations through selective hybridizations. The identification and analysis of these sequence variations enables positive discrimination of isolates of the group that includes . Discrimination of single base differences in rRNA was achieved with a microchip during analysis of group isolates from both single and in mixed probes, as well as identification of polymorphic sites. Successful use of a microchip to determine the appropriate subgroup classification using eight reference microorganisms from the group as a study set, was demonstrated.