Gamma-Butyrolactone Regulatory System of Streptomyces chattanoogensis Links Nutrient Utilization, Metabolism, and Development

Abstract

Gamma-butyrolactones (GBLs) produced by several Streptomyces species have been shown to serve as quorum-sensing signaling molecules for activating antibiotic production. The GBL system of Streptomyces chattanoogensis L10, a producer of antifungal agent natamycin, consists of three genes: scgA, scgX, and scgR. Both scgA and scgX contribute to GBL production, while scgR encodes a GBL receptor. ⌬scgA and ⌬scgX mutants of S. chattanoogensis behaved identically: they had a growth defect in submerged cultures and delayed or abolished the morphological differentiation and secondary metabolites production on solid medium. ScgR could bind to the promoter region of scgA and repress its transcription. Moreover, scgA seems also to be controlled by a GBL-mediated negative-feedback system. Hence, it is apparent that GBL biosynthesis is tightly controlled to ensure the correct timing for metabolic switch. An additional direct ScgR-target gene gbdA was identified by genomic SELEX and transcriptional analysis. Comparative proteomic analysis between L10 and its ⌬scgA mutant revealed that the GBL system affects the expression of more than 50 proteins, including enzymes involved in carbon uptake system, primary metabolism, and stress response, we thus conclude that scgR-scgA-scgX constitute a novel GBL regulatory system involved in nutrient utilization, triggering adaptive responses, and finally dictating the switch from primary to secondary metabolism. Quorum sensing (QS) is a cell-cell communication processin which bacteria use the production and detection of extracellular chemicals called autoinducers to monitor cell population density and synchronize community behavior through regulation of their gene expression in response to changes in cell density. Acyl homoserine lactones (AHLs) are a major class of autoinducers used by Gram-negative proteobacteria for intraspecies quorum sensing (23) and has been studied intensively over the past decade. Streptomyces, probably as well as its related genera, use ␥-butyrolactones (2,3-di-substituted-␥-butyrolactones) as autoinducers, the chemical structure of which is similar to that of AHLs except for the carbon side chain (31). In addition, other signal molecules, such as PI factor [2,3-diamino-2,3-bis(hydroxymethyl)-1,4-butanediol] and AHFCAs (2-alkyl-4-hydroxymethylfuran-3-carboxylic acids), have been described to play a similar role to that of GBLs in Streptomyces (6, 26).Streptomycetes are Gram-positive soil bacteria that undergo a developmental program that leads to sporulating aerial hyphae. They are also characterized by a complex secondary metabolism, which makes them the largest antibiotic-producing genus, producing over two-thirds of the clinically used antibiotics of natural origin. The ␥-butyrolactone (GBL) system of Streptomyces, typically consisting of a GBL synthase and a cognate receptor, is drawing more attention because of its close association with production of several antibiotics (31). Currently, there are four such systems with a known GBL and receptor, including the ...

Necrotizing enterocolitis is preceded by increased gut bacterial replication, Klebsiella, and fimbriae-encoding bacteria that may stimulate TLR4 receptors

“…The most significant secondary metabolite gene cluster encodes an unusual operon of biosynthetic genes found in Klebsiella (cluster 416) . In other species, similar operons are implicated in biosynthesis of quorum sensing butyrolactones 20 . The second most significant cluster of genes occurs in Enterococcus and is involved in biosynthesis of a sactipeptide resembling subtilosin A1, an antimicrobial agent with known hemolytic activity 21 (cluster 438) ( Supplemental Table S5 ).…”

WblAch, a Pivotal Activator of Natamycin Biosynthesis and Morphological Differentiation in Streptomyces chattanoogensis L10, Is Positively Regulated by AdpAch

“…An Agilent HC-C 18 column (5 m, 4.6 by 250 mm) was used, and the UV detector was set at 303 nm. The mobile phase and gradient elution processes were previously described (30).…”

Improvement of Natamycin Production by Engineering of Phosphopantetheinyl Transferases in Streptomyces chattanoogensis L10

“…factors related to NTM biosynthesis have been well studied to improve NTM production, including the pathway-specific regulators (14)(15)(16), the gamma-butyrolactone regulatory system (17,18), the pimaricin inducer (PI) factor system (19,20), the P450 epoxidase (21), the phosphate regulation system (22), the pleiotropic regulatory system (23), and the exporter (24). We have previously cloned the scn PKS NTM biosynthetic gene cluster in S. chattanoogensis L10 (14,23).…”