Mapping the Trimethoprim-Induced Secondary Metabolome of <i>Burkholderia thailandensis</i>

Okada, Bethany K.; Wu, Yihan; Mao, Dainan; Bushin, Leah B.; Seyedsayamdost, Mohammad R.

doi:10.1021/acschembio.6b00447

Cited by 63 publications

(99 citation statements)

References 32 publications

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“…Since many clinically relevant antibiotics and other therapeutics are derived from natural products, triggering the expression of these cryptic gene clusters under laboratory growth conditions is of significant interest. 4, 5 …”

Section: Introductionmentioning

confidence: 99%

Global Awakening of Cryptic Biosynthetic Gene Clusters in Burkholderia thailandensis

et al. 2017

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Many bacteria encode biosynthetic proteins that produce a vast array of natural products. These compounds are often synthesized during host invasion as they function as virulence factors. In addition, such secondary metabolites have yielded numerous molecular scaffolds with pharmaceutical and clinical importance. The gene clusters that encode proteins responsible for synthesis of these compounds are typically silenced or “cryptic” under laboratory growth conditions, hampering discovery of novel lead compounds. We report here that MftR is a global repressor of secondary metabolite synthesis in Burkholderia thailandensis and that urate functions as a physiologically relevant inducer of gene expression. Biosynthetic gene clusters under MftR control include those associated with production of the antimicrobial bactobolins, the iron siderophore malleobactin, and the virulence factor malleilactone. MftR also controls additional genes associated with survival in a host environment, such as genes encoding components of the type III secretion system (T3SS) and proteins linked to anaerobic respiration. This observation not only has implications for understanding activation of gene regulatory networks during host invasion, but it also paves the way for isolation of novel therapeutic leads.

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Section: Introductionmentioning

confidence: 99%

Global Awakening of Cryptic Biosynthetic Gene Clusters in Burkholderia thailandensis

et al. 2017

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“…The results showed major induction of a number of metabolites in ΔscmR (Fig. 3A)-notably, burkholdac, malleilactone, thailandamide, and acybolins (11) (23). Specifically, in the mutant strain malleilactone A, burkholdac A, thailandamide A, and acybolin A were overproduced 210-, 61-, 54-, and 18-fold, respectively.…”

Section: Resultsmentioning

confidence: 95%

Discovery of scmR as a global regulator of secondary metabolism and virulence in Burkholderia thailandensis E264

Mao

Bushin

Moon

et al. 2017

Proc. Natl. Acad. Sci. U.S.A.

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Bacteria produce a diverse array of secondary metabolites that have been invaluable in the clinic and in research. These metabolites are synthesized by dedicated biosynthetic gene clusters (BGCs), which assemble architecturally complex molecules from simple building blocks. The majority of BGCs in a given bacterium are not expressed under normal laboratory growth conditions, and our understanding of how they are silenced is in its infancy. Here, we have addressed this question in the Gram-negative model bacterium Burkholderia thailandensis E264 using genetic, transcriptomic, metabolomic, and chemical approaches. We report that a previously unknown, quorum-sensing-controlled LysR-type transcriptional regulator, which we name ScmR (for secondary metabolite regulator), serves as a global gatekeeper of secondary metabolism and a repressor of numerous BGCs. Transcriptionally, we find that 13 of the 20 BGCs in B. thailandensis are significantly (threefold or more) upor down-regulated in a scmR deletion mutant (ΔscmR). Metabolically, the ΔscmR strain displays a hyperactive phenotype relative to wild type and overproduces a number of compound families by 18-to 210-fold, including the silent virulence factor malleilactone. Accordingly, the ΔscmR mutant is hypervirulent both in vitro and in a Caenorhabditis elegans model in vivo. Aside from secondary metabolism, ScmR also represses biofilm formation and transcriptionally activates ATP synthesis and stress response. Collectively, our data suggest that ScmR is a pleiotropic regulator of secondary metabolism, virulence, biofilm formation, and other stationary phase processes. A model for how the interplay of ScmR with pathwayspecific transcriptional regulators coordinately silences virulence factor production is proposed.biosynthetic gene clusters | natural products | Burkholderia thailandensis | regulation | virulence

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“…Moreover, the elicitors can be pleiotropic and give rise to numerous other secondary metabolites, thus facilitating small molecule discovery in a global and pathway-specific manner simultaneously. 13,14 Lastly, with small molecule probes at hand to modulate the expression of a cluster, the regulatory pathways can be examined.…”

Section: Discussionmentioning

confidence: 99%

Discovery of a Cryptic Antifungal Compound from Streptomyces albus J1074 Using High-Throughput Elicitor Screens

et al. 2017

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An important unresolved issue in microbial secondary metabolite production is the abundance of biosynthetic gene clusters that are not expressed under typical laboratory growth conditions. These so-called silent or cryptic gene clusters are sources of new natural products, but how they are silenced, and how they may be rationally activated are areas of ongoing investigation. We recently devised a chemogenetic high-throughput screening approach (“HiTES”) to discover small molecule elicitors of silent biosynthetic gene clusters. This method was successfully applied to a Gram-negative bacterium; it has yet to be implemented in the prolific antibiotic-producing streptomycetes. Herein we have developed a high-throughput transcriptional assay format in Streptomyces spp. by leveraging eGFP, inserted both at a neutral site and inside the biosynthetic cluster of interest, as a read-out for secondary metabolite synthesis. Using this approach, we successfully used HiTES to activate a silent gene cluster in Streptomyces albus J1074. Our results revealed the cytotoxins etoposide and ivermectin as potent inducers, allowing us to isolate and structurally characterize 14 novel small molecule products of the chosen cluster. One of these molecules is a novel antifungal, while several others inhibit a cysteine protease implicated in cancer. Studies addressing the mechanism of induction by the two elicitors led to the identification of a pathway-specific transcriptional repressor that silences the gene cluster under standard growth conditions. The successful application of HiTES will allow future interrogations of the biological regulation and chemical output of the countless silent gene clusters in Streptomyces spp.

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Mapping the Trimethoprim-Induced Secondary Metabolome of Burkholderia thailandensis

Cited by 63 publications

References 32 publications

Global Awakening of Cryptic Biosynthetic Gene Clusters in Burkholderia thailandensis

Global Awakening of Cryptic Biosynthetic Gene Clusters in Burkholderia thailandensis

Discovery of scmR as a global regulator of secondary metabolism and virulence in Burkholderia thailandensis E264

Discovery of a Cryptic Antifungal Compound from Streptomyces albus J1074 Using High-Throughput Elicitor Screens

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