Rice bacterial blight pathogen Xanthomonas oryzae pv. oryzae produces multiple DSF-family signals in regulation of virulence factor production

<p>Abstract</p> <p>Background</p> <p><it>Xanthomonas </it><it>oryzae </it>pv. <it>oryzae </it>(<it>Xoo</it>) is the causal agent of rice bacterial blight disease. <it>Xoo </it>produces a range of virulence factors, including EPS, extracellular enzyme, iron-chelating siderophores, and type III-secretion dependent effectors, which are collectively essential for virulence. Genetic and genomics evidence suggest that <it>Xoo </it>might use the diffusible signal factor (DSF) type quorum sensing (QS) system to regulate the virulence factor production. However, little is known about the chemical structure of the DSF-like signal(s) produced by <it>Xoo </it>and the factors influencing the signal production.</p> <p>Results</p> <p><it>Xoo </it>genome harbours an <it>rpf </it>cluster comprising <it>rpfB</it>, <it>rpfF</it>, <it>rpfC </it>and <it>rpfG</it>. The proteins encoded by these genes are highly homologous to their counterparts in <it>X. campestris </it>pv. <it>campestris </it>(<it>Xcc</it>), suggesting that <it>Xcc </it>and <it>Xoo </it>might use similar mechanisms for DSF biosynthesis and autoregulation. Consistent with <it>in silico </it>analysis, the <it>rpfF </it>mutant was DSF-deficient and the <it>rpfC </it>mutant produced about 25 times higher DSF-like activity than the wild type <it>Xoo </it>strain KACC10331. From the supernatants of <it>rpfC </it>mutant, we purified three compounds showing strong DSF-like activity. Mass spectrometry and NMR analysis revealed that two of them were the previously characterized DSF and BDSF; the third one was a novel unsaturated fatty acid with 2 double bonds and was designated as CDSF in this study. Further analysis showed that all the three DSF-family signals were synthesized via the enzyme RpfF encoded by <it>Xoo2868</it>. DSF and BDSF at a final concentration of 3 μM to the <it>rpfF </it>mutant could fully restore its extracellular xylanase activity and EPS production to the wild type level, but CDSF was less active than DSF and BDSF in induction of EPS and xylanase. DSF and CDSF shared a similar cell density-dependent production time course with the maximum production being detected at 42 h after inoculation, whereas the maximum production of BDSF was observed at 36 h after inoculation. When grown in a rich medium such as YEB, LB, PSA, and NYG, <it>Xoo </it>produced all the three signals with the majority being DSF. Whereas in nutritionally poor XOLN medium <it>Xoo </it>only produced BDSF and DSF but the majority was BDSF.</p> <p>Conclusions</p> <p>This study demonstrates that <it>Xoo </it>and <it>Xcc </it>share the conserved mechanisms for DSF biosynthesis and autoregulation. <it>Xoo </it>produces DSF, BDSF and CDSF signals in rich media and CDSF is a novel signal in DSF-family with two double bonds. All the three DSF-family signals promote EPS production and xylanase activity in <it>Xoo</it>, but CDSF is less active than its analogues DSF and BDSF. The composition and ratio of the three DSF-family signals produced by <it>Xoo </it>are influenced by the composition of culture media.</p

Comparison of the metabolic responses of eight Escherichia coli strains including the “big six” in pea sprouts to low concentration electrolysed water by NMR spectroscopy

10.1016/j.foodcont.2021.108458Food Control131108458-10845

Structural and Functional Characterization of Diffusible Signal Factor Family Quorum-Sensing Signals Produced by Members of the Burkholderia cepacia Complex▿

Previous work has shown that Burkholderia cenocepacia produces the diffusible signal factor (DSF) family signal cis-2-dodecenoic acid (C12:Δ2, also known as BDSF), which is involved in the regulation of virulence. In this study, we determined whether C12:Δ2 production is conserved in other members of the Burkholderia cepacia complex (Bcc) by using a combination of high-performance liquid chromatography, mass spectrometry, and bioassays. Our results show that five Bcc species are capable of producing C12:Δ2 as a sole DSF family signal, while four species produce not only C12:Δ2 but also a new DSF family signal, which was identified as cis,cis-11-methyldodeca-2,5-dienoic acid (11-Me-C12:Δ2,5). In addition, we demonstrate that the quorum-sensing signal cis-11-methyl-2-dodecenoic acid (11-Me-C12:Δ2), which was originally identified in Xanthomonas campestris supernatants, is produced by Burkholderia multivorans. It is shown that, similar to 11-Me-C12:Δ2 and C12:Δ2, the newly identified molecule 11-Me-C12:Δ2,5 is a potent signal in the regulation of biofilm formation, the production of virulence factors, and the morphological transition of Candida albicans. These data provide evidence that DSF family molecules are highly conserved bacterial cell-cell communication signals that play key roles in the ecology of the organisms that produce them

Cyclohexyl-Fused, Spirobiindane-Derived, Phosphine-Catalyzed Synthesis of Tricyclic gamma-Lactams and Kinetic Resolution of gamma-Substituted Allenoates

10.1021/jacs.9b07418JOURNAL OF THE AMERICAN CHEMICAL SOCIETY1414116362-16373complete

New Stilbenoids Isolated from Fungus-Challenged Black Skin Peanut Seeds and Their Adipogenesis Inhibitory Activity in 3T3-L1 Cells

One new stilbene derivative (3,5,3′-trihydroxy-4′-methoxy-5′-isopentenylstilbene, MIP) and two new stilbene dimers (arahypin-11 and arahypin-12) together with three known stilbenoids (arachidin-1, arachidin-3, and SB-1) were isolated from black skin peanut seeds challenged by the fungal strain Rhizopus oligoporus. The structures of the three new compounds were elucidated by analysis of HRESIMS, UV, 1D and 2D NMR spectra. The antiadipogenic and cytotoxic effects of the isolated compounds were investigated using 3T3-L1 cells at a concentration range of 1–10 μM. Among the compounds tested, arachidin-1 inhibited the 3T3-L1 adipocyte differentiation dose-dependently, whereas arahypin-11 and arahypin-12 exhibited significant cytotoxicity in 3T3-L1 preadipocytes

Highly emissive, solution-processable and dynamic Eu(III)-containing coordination polymers

10.1039/c5cc01793aChemical Communications51418656-865

Light-Up Probe for Targeted and Activatable Photodynamic Therapy with Real-Time In Situ Reporting of Sensitizer Activation and Therapeutic Responses

10.1002/adfm.201502728Advanced Functional Materials25426586-659