Chloramphenicol resistance in Streptomyces coelicolor A3(2): Possible involvement of a transposable element

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Abstract
The transfer of a Chl element, causing resistance to chloramphenicol in Streptomyces coelicolor A3(2), was studied in NF x SCP1− superfertile crosses. When the Chl element is on the donor side (NF) its transfer to the recombinant cells was virtually total as if the element acted as a second concomitant transfer origin. When the Chl element was on the recipient side (SCP1−) it was never displaced by the immigrant chromosome even when the region facing chl + was selected for. A fraction of the original Chl− mutants presented a requirement for arginine (ArgB−). A Chl− mutant gave rise spontaneously to ArgB− derivatives at high frequency. The same ArgB− requirement come out at high frequency among Chl− derivatives from a cross NFChl− x SCP1−Chl+ in which neither parent required arginine or produced spontaneously arginineless derivatives. It is suggested that the Chl element is a “transposable element” (Tn) presumably associated with “insertion sequences” (IS). The insertional inactivation of the Chl element may be accompanied or followed by a deletion in the adjacent ArgB gene.