Characterization of the variable-number tandem repeats in vrrA from different Bacillus anthracis isolates

PCR analysis of 198 Bacillus anthracis isolates indicated a variable region of DNA sequence differing in length among the isolates. Five polymorphisms were characterized by the presence of two to six copies of the 12-bp tandem repeat 5'-CAATATCAACAA-3'. This variable-number tandem repeat region is found within a larger sequence containing one complete open reading frame that encodes a putative 30-kDa protein. Length variation did not alter the reading frame of the encoded protein and only modified the copy number of a 4-amino-acid sequence (QYQQ) from 2 to 6.