pH shock induces overexpression of regulatory and biosynthetic genes for actinorhodin productionin Streptomyces coelicolor A3(2)

Abstract

Actinorhodin production is markedly enhanced when an acidic pH shock is applied to a surface-grown culture of Streptomyces coelicolor A3(2). For an in-depth study of this phenomenon, transcriptional analyses using DNA microarrays and reverse transcription polymerase chain reaction and proteomic analysis were performed. Investigated were expression levels of the regulators and enzymes responsible for signal transduction and actinorhodin biosynthesis and enzymes involved in some major metabolic pathways. Regulators PkaG, AfsR, AfsS and/or another unidentified regulator and ActII-ORF4, in sequence, were observed to be activated by pH shock. In addition, a number of genes associated with actinorhodin production and secretion and the major central metabolic pathways investigated were observed to be upregulated with pH shock. Fatty acid degradation was particularly promoted by pH shock, while fatty acid biosynthesis was suppressed; it is envisaged that this enriches the precursor pool (acetyl-CoA) and building blocks for actinorhodin biosynthesis. Furthermore, glucose 6-phosphate dehydrogenases, initiating the pentose phosphate pathway, were highly activated by pH shock, enriching the reduced nicotinamide adenine dinucleotide phosphate (NADPH) pool for biosynthesis in general. It is deduced that these metabolic changes caused by pH shock have positively contributed to the stimulation of actinorhodin biosynthesis in a concerted manner.

Nutritional requirements for the production of antimicrobial metabolites from Streptomyces

“…It is well known that environmental signals, including pH shock, can stimulate and promote the biosynthesis of secondary metabolites. Kim et al (2007) reported that when the pH was maintained at 5, production of geldanamycin was increased from 414 to 768 mg/L. Nadia et al (2004) studied the effects of temperature, pH, incubation period, some media and different nitrogen and carbon sources for the production of antimicrobial metabolite production.…”

Putative TetR Family Transcriptional Regulator SCO1712 Encodes an Antibiotic Downregulator in Streptomyces coelicolor

“…Recently, so-called "-omics-guided reverse engineering" approaches, including comparative transcriptomics and proteomics, were successfully used to identify alterations in gene expression associated with the overproduction of secondary metabolites in industrial streptomyces strains (9,10,11,12,13). Especially, interspecies genome-wide screening using S. coelicolor cDNA microarrays together with antibiotic-overproducing industrial strains of related streptomycetes led to the discovery of putative global downregulator genes affected by unidentified mutations in the industrial strains (9,14).…”

Functional expression of SCO7832 stimulates tautomycetin production via pathway-specific regulatory gene overexpression in Streptomyces sp. CK4412

“…It has been reported that production of the antibiotic actinorhodin was signiWcantly enhanced when an acidic pH shock was applied to surface cultures of S. coelicolor [20,21]. Among many over-expressed genes identiWed from S. coelicolor DNA microarrays [19,20], several Na + /H + antiporter genes including SCO7832 were also identiWed as pH-shock-induced potential target genes.…”

“…The well-characterized pathway-speciWc regulatory proteins including ActII-ORF4 for actinorhodin biosynthesis from S. coelicolor belong to the so-called Streptomyces Antibiotic Regulatory Proteins (SARPs) family [16]. Another important transcriptional family of regulators that belong to the so-called LAL (Large ATPbinding regulators of the LuxR) family have also been identiWed and characterized in several macrolide antibiotic pathways including TmcN for tautomycetin [20].…”

“…Among many over-expressed genes identiWed from S. coelicolor DNA microarrays [19,20], several Na + /H + antiporter genes including SCO7832 were also identiWed as pH-shock-induced potential target genes. Moreover, the SCO7832 cloned in a high-copy plasmid pWHM3 in S. lividans stimulated the actinorhodin production in both plate and liquid cultures (Kim et al unpublished data).…”