Sources of Diversity in Bactobolin Biosynthesis by <i>Burkholderia thailandensis</i> E264

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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“…42, 43 Many genes in the bactobolin gene cluster are upregulated >20-fold in absence of MftR (Table 1 and Fig. S5).…”

Section: Resultsmentioning

confidence: 99%

Global Awakening of Cryptic Biosynthetic Gene Clusters in Burkholderia thailandensis

et al. 2017

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“…This bactobolin was estimated to be at 5.3 mg ml À 1 in pure Bt culture fluid in growth conditions similar to those we use (Seyedsayamdost et al, 2010). Bt produces at least seven other bactobolin compounds (Seyedsayamdost et al, 2010;Carr et al, 2011). To test if Bt-produced bactobolins in cell culture fluid are sufficient to kill Cv, we assessed Cv viability after treatment with filtered fluid from a stationary-phase (OD 600 8-10) Bt culture.…”

Section: Antibiotic Sensitivitiesmentioning

confidence: 99%

“…Finally, BtaR2-I2 senses and produces 3-hydroxy-octanoyl-HSL and 3-hydroxy-decanoyl-HSL . The BtaR2-I2 system activates btaI2 and a set of genes responsible for the production of a family of hydrophilic antibiotics, the bactobolins, that have activity against a broad range of bacterial species Seyedsayamdost et al, 2010;Carr et al, 2011) including Cv (see below). The most potent of these is bactobolin A (Carr et al, 2011).…”

Section: Introductionmentioning

confidence: 99%

Acyl-homoserine lactone-dependent eavesdropping promotes competition in a laboratory co-culture model

et al. 2012

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Many Proteobacteria use acyl-homoserine lactone (AHL)-mediated quorum sensing to activate the production of antibiotics at high cell density. Extracellular factors like antibiotics can be considered public goods shared by individuals within a group. Quorum-sensing control of antibiotic production may be important for protecting a niche or competing for limited resources in mixed bacterial communities. To begin to investigate the role of quorum sensing in interspecies competition, we developed a dual-species co-culture model using the soil saprophytes Burkholderia thailandensis (Bt) and Chromobacterium violaceum (Cv). These bacteria require quorum sensing to activate the production of antimicrobial factors that inhibit growth of the other species. We demonstrate that quorum-sensing-dependent antimicrobials can provide a competitive advantage to either Bt or Cv by inhibiting growth of the other species in co-culture. Although the quorum-sensing signals differ for each species, we show that the promiscuous signal receptor encoded by Cv can sense signals produced by Bt, and that this ability to eavesdrop on Bt can provide Cv an advantage in certain situations. We use an in silico approach to investigate the effect of eavesdropping in competition, and show conditions where early activation of antibiotic production resulting from eavesdropping can promote competitiveness. Our work supports the idea that quorum sensing is important for interspecies competition and that promiscuous signal receptors allow eavesdropping on competitors in mixed microbial habitats.

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“…1). Some of the bactobolins are potent antibiotics (2, 3). These water-soluble compounds consist of a C 6 -polyketide fused to a chlorinated hydroxy-valine residue.…”

Section: Introductionmentioning

confidence: 99%

“…Preparations were toxic to mammalian cells, and perhaps because of this, the interest in bactobolins waned (3–5). We recently discovered five new bactobolins (D to H) and a cluster of genes involved in bactobolin biosynthesis (the genes are BTH_II1222 to BTH_II1242 from genomic coordinates 1445675 to 1482269; see ), which is reasonably well conserved in the related species Burkholderia pseudomallei (2, 3, 6). We also showed that bactobolin production is dependent on one of the three acyl-homoserine lactone (acyl-HSL) quorum-sensing circuits in B. thailandensis , the BtaI2–BtaR2– N -3-hydroxydecanoyl HSL (3OHC 10 -HSL) circuit (6).…”

Section: Introductionmentioning

confidence: 99%

Bactobolin Resistance Is Conferred by Mutations in the L2 Ribosomal Protein

Chandler

Truong

Silva

et al. 2012

mBio

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Burkholderia thailandensis produces a family of polyketide-peptide molecules called bactobolins, some of which are potent antibiotics. We found that growth of B. thailandensis at 30°C versus that at 37°C resulted in increased production of bactobolins. We purified the three most abundant bactobolins and determined their activities against a battery of bacteria and mouse fibroblasts. Two of the three compounds showed strong activities against both bacteria and fibroblasts. The third analog was much less potent in both assays. These results suggested that the target of bactobolins might be conserved across bacteria and mammalian cells. To learn about the mechanism of bactobolin activity, we isolated four spontaneous bactobolin-resistant Bacillus subtilis mutants. We used genomic sequencing technology to show that each of the four resistant variants had mutations in rplB, which codes for the 50S ribosome-associated L2 protein. Ectopic expression of a mutant rplB gene in wild-type B. subtilis conferred bactobolin resistance. Finally, the L2 mutations did not confer resistance to other antibiotics known to interfere with ribosome function. Our data indicate that bactobolins target the L2 protein or a nearby site and that this is not the target of other antibiotics. We presume that the mammalian target of bactobolins involves the eukaryotic homolog of L2 (L8e).

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Sources of Diversity in Bactobolin Biosynthesis by Burkholderia thailandensis E264

Cited by 38 publications

References 26 publications

Global Awakening of Cryptic Biosynthetic Gene Clusters in Burkholderia thailandensis

Global Awakening of Cryptic Biosynthetic Gene Clusters in Burkholderia thailandensis

Acyl-homoserine lactone-dependent eavesdropping promotes competition in a laboratory co-culture model

Bactobolin Resistance Is Conferred by Mutations in the L2 Ribosomal Protein

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