Impact of otrAexpression on morphological differentiation, actinorhodin production, and resistance to aminoglycosides in Streptomyces coelicolorM145

otrAresembles elongation factor G (EF-G) and is considered to be an oxytetracycline (OTC)-resistance determinant in Streptomyces rimosus. In order to determine whether otrAalso conferred resistance to OTC and other aminoglycosides to Streptomyces coelicolor, the otrAgene from S. rimosusM527 was cloned under the control of the strong ermE* promoter. The resulting plasmid, pIB139-otrA, was introduced into S. coelicolorM145 by intergeneric conjugation, yielding the recombinant strain S. coelicolorM145-OA. As expected S. coelicolorM145-OA exhibited higher resistance levels specifically to OTC and aminoglycosides gentamycin, hygromycin, streptomycin, and spectinomycin. However, unexpectedly, S. coelicolorM145-OA on solid medium showed an accelerated aerial mycelia formation, a precocious sporulation, and an enhanced actinorhodin (Act) production. Upon growth in 5-L fermentor, the amount of intra- and extracellular Act production was 6-fold and 2-fold higher, respectively, than that of the original strain. Consistently, reverse transcription polymerase chain reaction (RT-PCR) analysis revealed that the transcriptional level of pathway-specific regulatory gene actII-orf4was significantly enhanced in S. coelicolorM145-OA compared with in S. coelicolorM145.