Developmental regulator RamRsl controls both morphological development and lincomycin biosynthesis in Streptomyces lincolnensis

Abstract

Aims: Assessing the role of ramR sl , a gene absent in a lincomycin over-producing strain, in the regulation of morphological development and lincomycin biosynthesis in Streptomyces lincolnensis. Methods and Results:The gene ramR sl was deleted from the wild-type strain NRRL 2936 and the ΔramR mutant strain was characterized by a slower growth rate and a delayed morphological differentiation compared to the original strain NRRL 2936. Furthermore, the ΔramR produced 2.6-fold more lincomycin than the original strain, and consistently the level of expression of all lincomycin cluster located genes was enhanced at 48 and 96 h in the ΔramR. Complementation of ΔramR with an intact copy of ramR sl restored all wild-type features, whereas the over-expression of ramR sl led to a reduction of 33% of the lincomycin yield. Furthermore, the level of expression of glnR, bldA and SLCG_2919, three of known lincomycin biosynthesis regulators, was lower in the ΔramR than in the original strain at the early stage of fermentation and we demonstrated, using electrophoretic mobility shift assay and XylE reporter assay, that glnR is a novel direct target of RamR.Conclusions: Altogether, these results indicated that, beyond promoting the morphological development, RamR regulates negatively lincomycin biosynthesis and positively the expression of the nitrogen regulator GlnR. Significance and Impact of the Study:We demonstrated that RamR plays a negative role in the regulation of lincomycin biosynthesis in S. lincolnensis. Interestingly, the deletion of this gene in other antibiotic-producing Streptomyces strains might also increase their antibiotic-producing abilities.

An alternative σ factor σLsl regulates lincomycin production in Streptomyces lincolnensis

“…Fermentation of S. lincolnensis strains and lincomycin bioassay detection referred to previously established procedures [19].…”

“…Micrococcus luteus 28001 cultivated on solid medium Ⅲ at 37°C was used for lincomycin bioassay analysis [11]. Streptomyces lincolnensis strains were cultured (at 28°C) on solid MS medium for daily culture, on solid ISP4 medium for conjugation, in liquid YEME medium for cellular growth detection [25], and in SFP Ⅰ&Ⅱ medium for fermentation [19]. The media were supplemented with apramycin of 50 μg/ml and kanamycin of 50 μg/ml as appropriate.…”

“…As previously reported, a CRISPR/Cas9-mediated genetic editing procedure was employed to delete sigL sl in S. lincolnensis NRRL 2936 [19]. The upstream and downstream homologous arms of the sigL sl gene were amplified by polymerase chain reaction (PCR) using primer pairs UsigL-F/R and DsigL-F/R.…”

“…LmbU was identified as a cluster-situated regulator (CSR) to promote lincomycin biosynthesis [11,14], and its transcription can be induced by ATPase LmrC [13]. Furthermore, the transcriptional regulators AdpA [15], BldD [16], GlnR [17], and SLCG_Lrp [18] stimulates lincomycin biosynthesis, while regulator RamR sl [19] and TetR family regulator SLCG_2919 repress lincomycin biosynthesis [20]. However, the regulatory mechanism of lincomycin biosynthesis still requires to be explored.…”

AdpAlin regulates lincomycin and melanin biosynthesis by modulating precursors flux in Streptomyces lincolnensis

“…Transcriptional regulators determine the most appropriate timing and level of transcription and result in an elaborate balance of secondary metabolism in Streptomyces [8]. In Streptomyces lincolnensis , several transcriptional regulators, such as LmbU [9], GlnR [10], BldD [11], and RamR [12], have been proven to compose a complex regulation network. However, compared with other well‐studied antibiotics, research on the mechanisms of transcriptional regulators proceed much slower in S. lincolnensis .…”