Repression of Antibiotic Production and Sporulation inStreptomyces coelicolorby Overexpression of a TetR Family Transcriptional Regulator

Abstract

The development of the Gram-positive genus Streptomyces is characterized by a complex morphological differentiation process thought to be triggered by conditions of nutritional limitation that often correlate with high cell density (41). This process includes the arising of an aerial mycelium from the vegetative mycelium and then the differentiation of the tips of the aerial hyphae into spores (10, 15). This process is coupled to a metabolic differentiation that correlates with the production of a wide range of pharmaceutically important secondary metabolites, including antibacterial, anticancer, and immunosuppressive drugs (8, 10). The genes responsible for the biosynthesis of these secondary metabolites are clustered in the genome and coordinately regulated by pathway-specific transcriptional regulators (1,4,18,19,62,70). The expression of these specific regulators linked to the biosynthetic pathways is directly or indirectly controlled either by positive pleiotropic regulators, such as AfsR2 (69), AfsS (29), AtrA (65), PtpA (67), PkaD (68), and the two-component systems AfsK/AfsR (66) and EcrA1/EcrA2 (39), by negative regulators, including the two-component systems AbsA1/AbsA2 (44), PhoR/PhoP (55), and CutR/CutS (9), or by enzymatic systems, such as Ppk (16). The pleiotropic regulators, thought to sense a variety of extracellular or intracellular signals related to nutriment availability, cell crowding, or energy shortage, are necessary to trigger the necessary metabolic adjustments to adapt to these conditions (27, 43), whereas the ppk gene is thought to act as an ATP-regenerating enzyme (54).Streptomyces coelicolor A3 (2) is usually used as the reference strain to study morphological and metabolic differentiation in relation with antibiotic biosynthesis (10, 15). S. coelicolor has long been known to produce four major antibiotics, actinorhodin (ACT) (40), undecylprodigiosin (RED) (13), methylenomycin (MMY) (36), and calcium-dependent antibiotic (CDA) (21), and recently, two novel ones were characterized, CPK, a putative type I polyketide (17, 50), and albaflavenone, a sesquiterpene antibiotic (72). ACT is a secondary metabolite of the polyketide family that is strongly produced by S. coelicolor but only weakly produced by its close relative, Streptomyces lividans. However, S. lividans has the genetic capability to produce this compound since the weak production of ACT could be stimulated by various genetic manipulations that include the overexpression of the pathway-specific activator gene actII-ORF4 (7), the afsR and afsR2 (now afsS) genes (35), the rep gene (42), and the phosphotyrosine protein phosphataseencoding gene ptpA (67). The inactivation of other genes, such as ppk (11), or mutations in the rpoB gene (25) or in the ribosomal protein S12 (23) are also leading to an enhancement of ACT production, indicating that ACT production was subjected to complex positive and negative controls. Furthermore, the extracellular addition of the signal molecule S-adenosylmethionine (34) or of ATP (38) or the replac...

A MarR Family Transcriptional Regulator, DptR3, Activates Daptomycin Biosynthesis and Morphological Differentiation in Streptomyces roseosporus

“…5A and C), which is used frequently in Streptomyces. This finding indicates that dptR3 is transcribed as a leaderless mRNA, as are many other Streptomyces genes (27)(28)(29). The orf16 TSP was mapped to G at a position 50 nt upstream of the translational start codon of orf16.…”

The Absence of Pupylation (Prokaryotic Ubiquitin-Like Protein Modification) Affects Morphological and Physiological Differentiation in Streptomyces coelicolor

“…S. coelicolor produces several secondary metabolites, including blue-pigmented actinorhodin (ACT), red-pigmented prodiginines (RED), and nonpigmented calcium-dependent antibiotic (CDA) (37). ACT and RED were assayed in R2YE liquid medium (40). About 10 10 spores were used to inoculate 50 ml of R2YE medium in a 250-ml baffled flask.…”

“…Samples of 1 ml were taken for RED and ACT assays. The samples were centrifuged for 10 min; both the supernatant and the pellet (the mycelium) were used for ACT assays, whereas only the mycelium was used for RED assays (40). The production of CDA on Oxoid nutrient agar medium was evaluated by a bioassay using Micrococcus luteus as the indicator (41).…”

Anaerobic bacteria as producers of antibiotics

“…Particular stimuli like stress-inducing conditions, environmental cues, or signaling compounds need to be identified to induce changes in the metabolome Scherlach and Hertweck 2009). Alternatively, one may utilize either genetic engineering strategies including heterologous expression in a surrogate host, or the manipulation of biosynthesis gene regulation to induce gene expression in the wild-type strain (Girbal et al 2005;Mingardon et al 2011;Xu et al 2010). The ectopic overexpression of global or pathway-specific regulator genes can lead to an activation of gene cluster expression and production of the related compounds (Behnken et al 2012;Bergmann et al 2010;Corbell and Loper 1995;Ishida et al 2010).…”