Polyacrylamide gel electrophoresis of PstI digests of amplified omp2 gene fragments from Brucella prototype strains. The figure shows the three DNA fragments, the uncut DNA and the two PstI-digested DNA fragments, with sizes of 282, 238, and 44 bp, respectively. Lanes: M, molecular size ladder (in base pairs); 1, B. melitensis strain 16M (uncut); 2, B. melitensis strain 16M; 3, B. melitensis vaccine strain Rev.1 (subcutaneous lot); 4, B. abortus vaccine S19; 5, B. abortus strain 544; 6, B. abortus strain 2308; 7, B. melitensis strain Ether.