Increasing the self-resistance levels of Streptomyces is an effective strategy to improve the production of antibiotics. To increase the oxytetracycline (OTC) production in Streptomyces rimosus, we investigated the cooperative effect of three co-overexpressing OTC resistance genes: one gene encodes a ribosomal protection protein (otrA) and the other two express efflux proteins (otrB and otrC). Results indicated that combinational overexpression of otrA, otrB, and otrC (MKABC) exerted a synergetic effect. OTC production increased by 179% in the recombinant strain compared with that of the wild-type strain M4018. The resistance level to OTC was increased by approximately two-fold relative to the parental strain, thereby indicating that applying the cooperative effect of self-resistance genes is useful to improve OTC production. Furthermore, the previously identified cluster-situated activator OtcR was overexpressed in MKABC in constructing the recombinant strain MKRABC; such strain can produce OTC of approximately 7.49 g L-1, which represents an increase of 19% in comparison with that of the OtcR-overexpressing strain alone. Our work showed that the cooperative overexpression of self-resistance genes is a promising strategy to enhance the antibiotics production in Streptomyces.
Keywords: Streptomyces rimosus; cluster-situated activator; combinatorial overexpression; oxytetracycline; resistance genes.