Expression analysis of regulatory genes in streptomyces lividans TK24 with foreign bacterial hemoglobin genes

Abstract

It was reported that the introduction of hemoglobin genes into the host microorganism enhanced the production of various bioproducts. In this study, bacterial hemoglobin genes from Vitreoscilla stercoraria and Sinorhizobium meliloti were transformed into Streptomyces lividans TK24, and it was observed that the growth rate and secondary metabolites (actinorhodin and undecylprodigiosin) productivity dramatically increased with noticeable changes in organic acids production pattern. These results suggested that the genetic transfer of bacterial hemoglobin genes into S. lividans TK24 might have affected both of its primary and secondary metabolisms. A transcriptional analysis based on reverse transcription-polymerase chain reaction (RT-PCR) and Northern blot analysis was performed, to monitor the expression of various regulatory genes and antioxidant enzyme genes, and thus to understand the mechanism of the enhanced productivity. The target genes were in the following three groups: pathway specific regulatory genes (actll-orf4, redD, cdaR ); pleiotropic regulatory genes (metK, afsQ1, cutR, afsR, , relA, ppk, phoP, and LysR-type transcriptional regulator orf10) and antioxidant enzyme genes(catA, catB, sodN, and sodF,). It was observed that the introduction of bacterial hemoglobin genes increased the transcription of most of the pathway specific regulatory genes tested. However, it increased the transcription of some of the pleiotropic regulatory genes, but decreased the transcription of the other pleiotropic regulatory genes. catA, the major catalase, was induced by bacterial hemoglobin genes during the early growth and stationary phase and it might have had the main role responsing the oxidative stress.