Some bacterial species are capable of producing a variety of secondary metabolites, but usually only in small amounts. One way to achieve higher yields is to improve the producing strain. One possible option is to enhance its self-resistance to the metabolite it produces, for example, by overexpressing efflux proteins. Our aim was to insert an additional copy of the genes otrB and otrC, representing membrane efflux transporters, into three strains of Streptomyces rimosus bacteria. The aim of this work was to investigate the effect of overexpression of these genes on the production of TC analogues, more specifically OTC and ATC in different strains of S. rimosus. After construction of plasmids containing a membrane efflux transporter gene and a constitutive promoter, the plasmids were introduced into four S. rimosus strains by conjugation. The newly obtained exconjugants were then compared with controls for secondary metabolite production. We found that introduction of membrane pumps OtrB and OtrC into the wild type strain S. rimosus ATCC 10970 and the industrial strain S. rimosus HP0508 did not increase the yield of OTC compared to the control strains with the exception of S. rimosus ATCC 10970::OtrC, which showed up to 32% improvement in the production of OTC. However, in the case of S. rimosus BF _7S strain, we found that increased expression of OtrB and OtrC membrane pumps contributed to a significant, up to 18-fold improvement in ATC production.
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