CONSERVATION OF THE ORGANIZATION OF THE STREPTOKINASE GENE REGION AMONG PATHOGENIC STREPTOCOCCI

Using ten gene-specific probes from the cloned and sequenced streptoki nase gene (skc) region (8 931 bp) of Streptococcus equisimilis H46A, a human serogroup C strain, the conservation of these genes and their l inkage relationships were studied by Southern hybridization in pathoge nic streptococci differing taxonomically, serologically, in regard to their host range, and in the class of plasminogen activator produced. The results indicate that in S. pyogenes (strains A374, NZ131 and SF13 0/13) and a human group G strain (G19 908) both gene content and gene order as determined for H46A (dexB-abc-lrp-skc-orfl-rel) are preserved . The same is true of an equine S. equisimilis isolate (87-542-W), the streptokinase gene of which has been shown to hybridize detectably wi th skc, a result at variance with that obtained previously by others. In contrast, the chromosomal DNA of three S. uberis strains (0140J, C1 98, C216) of bovine origin, two of which produced a plasminogen activa tor different from streptokinase, hybridized only with dexB-, abc- and rel-specific probes, and the homologues of these genes appeared to li e close to each other. The maintenance of the organization of the stre ptokinase gene region in strains differing in overall chromosomal char acter suggests that this gene arrangement is of selective advantage.