A jumping gene in streptomyces coelicolor A3(2).

The difficulty in mapping the gene for chloramphenicol resistance (cmlR) in Streptomyces coelicolor A3(2) stock strains is possibly due to its location on different sites of the chromosome in various mixed subclones. Fresh isolates from CmlR strains show single unequivocal locations of cmlR. The same holds for CmlR strains derived as revertants from CmlS variants. The two best established sites for cmlR are one between cysA and metA, the other at right of argA, possibly in the right empty arc of the map (Fig. 2). The cmlR gene was assumed to be on a transposon (SCTn1), together with a gene for arginine-succinate synthase (argG), a gene for chromosome transfer (tra) and a gene for aereal mycelium formation (amy). In a CmlR revertant, the cmlR gene appears disjoined from argG (Fig. 5), thus showing the ability of SCTnl to be split and partially transposed. The possible wide occurrence of transposons in the genus Streptomyces is discussed.