The Onset of Tacrolimus Biosynthesis in Streptomyces tsukubaensis Is Dependent on the Intracellular Redox Status

Abstract

The oxidative stress response is a key mechanism that microorganisms have to adapt to changeling environmental conditions. Adaptation is achieved by a fine-tuned molecular response that extends its influence to primary and secondary metabolism. In the past, the role of the intracellular redox status in the biosynthesis of tacrolimus in Streptomyces tsukubaensis has been briefly acknowledged. Here, we investigate the impact of the oxidative stress response on tacrolimus biosynthesis in S. tsukubaensis. Physiological characterization of S. tsukubaensis showed that the onset of tacrolimus biosynthesis coincided with the induction of catalase activity. In addition, tacrolimus displays antioxidant properties and thus a controlled redox environment would be beneficial for its biosynthesis. In addition, S. tsukubaensis ∆ahpC strain, a strain defective in the H2O2-scavenging enzyme AhpC, showed increased production of tacrolimus. Proteomic and transcriptomic studies revealed that the tacrolimus over-production phenotype was correlated with a metabolic rewiring leading to increased availability of tacrolimus biosynthetic precursors. Altogether, our results suggest that the carbon source, mainly used for cell growth, can trigger the production of tacrolimus by modulating the oxidative metabolism to favour a low oxidizing intracellular environment and redirecting the metabolic flux towards the increase availability of biosynthetic precursors.

Folding the unfoldable: using AlphaFold to explore spurious proteins

“…Most columns of the multiple alignment showed expected patterns of conservative substitution, with strong conservation of hydrophilic, hydrophobic, aromatic, small side chain size or Cys or Pro presence over a large fraction of residue positions. A search using the PaperBLAST resource ( Price and Arkin, 2017 ), allowing BLAST searches against all proteins whose accession numbers or locus tags are cited explicitly in Europe PubMedCentral ( Ferguson et al , 2021 ), found a protein with experimental evidence of gene expression that doubles in response to redox stress ( Pires et al , 2020 ). Lastly, we observed a broad species distribution of member sequences, from Actinobacteria to Cyanobacteria.…”

A Proteomic Analysis Indicates That Oxidative Stress Is the Common Feature Triggering Antibiotic Production in Streptomyces coelicolor and in the pptA Mutant of Streptomyces lividans

“…Interestingly, reports in the literature mention that other antibiotics have anti-oxidant properties and that their biosynthesis is induced in a condition of oxidative stress. In Streptomyces species these include tacrolimus produced by Streptomyces tsukubaensis ( Pires et al, 2020 ), pimaricin produced by Streptomyces natalensis ( Beites et al, 2011 , 2015 ), and chromomycin produced by Streptomyces flaviscleroticus ( Prajapati et al, 2018 ). Similar statements were made also for antibiotics produced by fungal species such as lovastatin produced by Aspergillus terreus ( Miranda et al, 2014 ), penicillin produced by Penicillium chrysogenum , and cephalosporin produced by Acremonium chrysogenum ( Bibian et al, 2020 ).…”

Metabolic adjustments in response to ATP spilling by the small DX protein in a Streptomyces strain

“…Such activation generates ATP but also OxS. The latter was proposed to be an important trigger of the biosynthesis of a specific class of quinone antibiotics with anti-oxidant properties ( Esnault et al, 2017 ; Millan-Oropeza et al, 2020 ; Pires et al, 2020 ; Beites et al, 2015 ; Prajapati et al, 2018 ; Beites et al, 2011 ; Virolle, 2020 ).…”

“…In consequence, an enforced systematic degradation of ATP is expected to stimulate these metabolic processes that contribute to ATP replenishment ( McKinlay et al, 2020 ). However, in all living organisms, the stimulation of oxidative metabolism generates oxidative stress (OxS) that could be detrimental to the cell ( Larosa and Remacle, 2018 ; Hirst and Roessler, 2016 ; Imlay, 2003 ) and in Streptomyces OxS was previously shown to trigger the production of bioactive specialized metabolites acting as anti-oxidants ( Millan-Oropeza et al, 2020 ; Pires et al, 2020 ; Beites et al, 2015 ; Prajapati et al, 2018 ; Beites et al, 2011 ) and that have a negative impact on respiration and thus on ATP generation ( Esnault et al, 2017 ; Virolle, 2020 ). From this, the development of biological tools able to reduce artificially ATP levels might result in the enhancement of the expression of already known or of unknown cryptic pathways present in the Streptomyces genomes and lead to the discovery of novel bioactive molecules useful to human health.…”

“…Finally, group 5 includes derivatives of hydroxyl-pyridine as well as polycyclic aromatic polyketide antibiotics belonging to the angucycline class. On the basis of previous studies, molecules with related structures and possessing quinone groups were proposed to have the ability to capture electrons of ROS/NOS and/or of the respiratory chain, having anti-oxidant ( Millan-Oropeza et al, 2020 ; Pires et al, 2020 ; Beites et al, 2015 ; Prajapati et al, 2018 ; Beites et al, 2011 ) as well as anti-respiratory properties ( Esnault et al, 2017 ; Virolle, 2020 ). The generation of class 4 and 5 molecules is thus proposed to contribute to the reduction of OxS and of ATP synthesis.…”