CtcS, a MarR family regulator, regulates chlortetracycline biosynthesis

Lingxin Kong,Zixin Deng,Jia Liu,Xiaoqing Zheng,Delin You

doi:10.1186/s12866-019-1670-9

Lingxin Kong, Zixin Deng + Show 3 more

Open Access

https://doi.org/10.1186/s12866-019-1670-9

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Abstract

BackgroundChlortetracycline (CTC) is one of the commercially important tetracyclines (TCs) family product and is mainly produced by Streptomyces. CTC is still in a great demand due to its broad-spectrum activity against pathogens. Engineering transcriptional control allows the cell to allocate its valuable resources towards protein production and provides an important method for the build-up of desired metabolites. Despite extensive efforts concerning transcriptional regulation for increasing the productivities of TCs, the regulatory mechanisms of the CTC biosynthesis remain poorly understood.ResultsIn this study, the possible regulatory function of CtcS, a potential member of MarR (multiple antibiotic resistance regulator) family of transcriptional regulators in S. aureofaciens F3, was demonstrated. Knockdown of ctcS altered the transcription of several biosynthesis-related genes and reduced the production of tetracycline (TC) and CTC, without obvious effect on morphological differentiation and cell growth. Especially, CtcS directly repressed the transcription of the adjacent divergent gene ctcR (which encodes a putative TC resistance efflux protein). A CtcS-binding site was identified within the promoter region of ctcR by DNase I footprinting and an inverted repeat (5′-CTTGTC-3′) composed of two 6-nt half sites in the protected region was found. Moreover, both CTC and TC could attenuate the binding activity of CtcS with target DNA.ConclusionctcS regulated the production of TC and CTC in S. aureofaciens F3 and the overexpression of it could be used as a simple approach for the construction of engineering strain with higher productivity. Meanwhile, CtcS was characterized as a TC- and CTC-responsive MarR family regulator. This study provides a previously unrecognized function of CtcS and will benefit the research on the regulatory machinery of the MarR family regulators.

Highlights

Chlortetracycline (CTC) is one of the commercially important tetracyclines (TCs) family product and is mainly produced by Streptomyces
The Streptomyces antibiotic regulatory protein (SARP) family regulator NosP activated the transcription of structural genes for nosiheptide biosynthesis [9] and responded to both peptidyl and small-molecule ligands derived from the precursor peptide [10]
The nucleotide sequences and deduced amino acid sequences of ctcR-S are highly homologous to those of otrB-R involved in the OTC biosynthesis in S. rimosus

Summary

Introduction

Chlortetracycline (CTC) is one of the commercially important tetracyclines (TCs) family product and is mainly produced by Streptomyces. The Streptomyces antibiotic regulatory protein (SARP) family regulator NosP activated the transcription of structural genes for nosiheptide biosynthesis [9] and responded to both peptidyl and small-molecule ligands derived from the precursor peptide [10]. MarR family transcriptional regulators have been identified in antibiotic biosynthesis gene cluster. The homologous protein of OtcR was reported to activate the expression of oxy cluster in heterologous host S. coelicolor CH999 [11] and Streptomyces lividans K4–114 [12]. Taking the reported phosphate-mediated control of OTC production into account, a more complex ‘fine tuning’ role of OtcG in overall expression of genes for OTC biosynthesis was envisaged [13]. The utilization of transcriptional control engineering for high yield strain constructions is largely dependent on the elucidation of the regulatory system, which in the case of CTC is still lacking

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