Characterization and Localization of Plasmid Functions Involved in Pock Formation and Pock Resistance of Plasmid pSK3of Streptomyces kasugaensis MB273

Department of Antibiotics, The National Institute of Health, 10-35 Kamiosaki 2-Chome, Shinagawa-Ku, Tokyo, 141, Japan ABSTRACT SUMMARY: Deletion derivatives and recombinants of the plasmid pSK3 * , which is a cointegrate of pSK1 * and pSK2 * in Streptomyces kasugaensis , were constructed and analysed for their ability to transfer and ‘pock’ on strains carrying pSK1 * or pSK2 * . Various deletions in the pSK1 * and/or pSK2 * regions of pSK3 * were grouped into nine classes on the basis of their pock-forming ability and pock resistance. Analysis of these deletions and insertions provided tentative locations of DNA regions for two pock-resistance determinants (Porl and Por2), two pock-forming determinants (Poc1 and Poc2) consisting of plasmid transfer and spread determinants (Tra/Spr), and two replication determinants (Rep1 and Rep2) corresponding to the pSK1 * and pSK2 * regions of pSK3 * . In particular, the Por2 function in the pSK2 * region was determined to be located in a 1·35 kb segment.