GENETIC-VARIABILITY OF BACILLUS-ANTHRACIS AND RELATED SPECIES

We evaluated the abilities of pulsed-field gel electrophoresis (PFGE) and sequences of intergenic spacer regions (ISRs) between two highly c onserved genes, 16S-23S rDNA and gyrB-gyrA ISRs, to detect variation i n strains of Bacillus anthracis as well as two closely related species , B. cereus ATCC 14579 and B. mycoides ATCC 6462. For each restriction enzyme, (NotI, SfiI, and SmaI), the PFGE banding patterns for three B . anthracis strains (Ames, Vollum, and Sterne) were identical, However , closely related species could be differentiated from B, anthracis an d from each other. PCR amplification of the 16S-23S rDNA ISR yielded a 143- to 144-bp fragment, shelving identical sequences for B. anthraci s strains, one nucleotide deletion between B. cereus and B. anthracis, and 13 nucleotide differences between B. mycoides and B. anthracis, T he gyrase ISR sequences (121 bp) in B. anthracis strains were also ide ntical, but those in B. cereus and B. mycoides differed from that in B . anthracis by 1 and 2 nucleotides, respectively, and from each other by only 1 nucleotide. Given the diverse geographic origins of these B. anthracis strains, this species is very homogenous, We conclude that methods such as PFGE and sequences of ISRs may be useful in separating B. anthracis from closely related species, but more sensitive methods are needed for strain identification of B. anthracis.