GENES FOR ALBICIDIN BIOSYNTHESIS AND RESISTANCE SPAN AT LEAST 69 KB IN THE GENOME OF XANTHOMONAS-ALBILINEANS

All Tn5 insertion mutants of Xanthomonas albilineans, the cause of lea f scald disease of sugar cane, which failed to produce albicidin antib iotics failed to cause chlorosis in inoculated sugar cane but- remaine d resistant to albicidin. Southern analysis revealed that mutants defi cient in albicidin production carried the transposon on different chro mosomal restriction fragments spanning at least: 50 kb in the X. albil ineans genome, which is larger than any reported cluster of genes invo lved in the production of a bacterial phytotoxin. Albicidin-resistant cosmid clones from a Tox(-) Tn5 insertion mutant did not carry the tra nsposon, and the subcloned albicidin resistance gene did not hybridize to any of the restriction fragments carrying Tn5 in the Tox(-) mutant s, indicating that the albicidin biosynthesis and resistance genes are not closely linked in X. albilineans.