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981.
Involvement of ralfuranones in the quorum sensing signalling pathway and virulence of Ralstonia solanacearum strain OE1‐1
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982.
Ralfuranones contribute to mushroom‐type biofilm formation by Ralstonia solanacearum strain OE1‐1
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Yuka Mori Yuki Hosoi Shiho Ishikawa Kazusa Hayashi Yu Asai Hideyuki Ohnishi Mika Shimatani Kanako Inoue Kenichi Ikeda Hitoshi Nakayashiki Yasuyo Nishimura Kouhei Ohnishi Akinori Kiba Kenji Kai Yasufumi Hikichi 《Molecular Plant Pathology》2018,19(4):975-985
After invasion into intercellular spaces of tomato plants, the soil‐borne, plant‐pathogenic Ralstonia solanacearum strain OE1‐1 forms mushroom‐shaped biofilms (mushroom‐type biofilms, mBFs) on tomato cells, leading to its virulence. The strain OE1‐1 produces aryl‐furanone secondary metabolites, ralfuranones (A, B, J, K and L), dependent on the quorum sensing (QS) system, with methyl 3‐hydroxymyristate (3‐OH MAME) synthesized by PhcB as a QS signal. Ralfuranones are associated with the feedback loop of the QS system. A ralfuranone productivity‐deficient mutant (ΔralA) exhibited significantly reduced growth in intercellular spaces compared with strain OE1‐1, losing its virulence. To analyse the function of ralfuranones in mBF formation by OE1‐1 cells, we observed cell aggregates of R. solanacearum strains statically incubated in tomato apoplast fluids on filters under a scanning electron microscope. The ΔralA strain formed significantly fewer microcolonies and mBFs than strain OE1‐1. Supplementation of ralfuranones A, B, J and K, but not L, significantly enhanced the development of mBF formation by ΔralA. Furthermore, a phcB‐ and ralA‐deleted mutant (ΔphcB/ralA) exhibited less formation of mBFs than OE1‐1, although a QS‐deficient, phcB‐deleted mutant formed mBFs similar to OE1‐1. Supplementation with 3‐OH MAME significantly reduced the formation of mBFs by ΔphcB/ralA. The application of each ralfuranone significantly increased the formation of mBFs by ΔphcB/ralA supplied with 3‐OH MAME. Together, our findings indicate that ralfuranones are implicated not only in the development of mBFs by strain OE1‐1, but also in the suppression of QS‐mediated negative regulation of mBF formation. 相似文献
983.
The mitochondrial membrane protein FgLetm1 regulates mitochondrial integrity,production of endogenous reactive oxygen species and mycotoxin biosynthesis in Fusarium graminearum
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Guangfei Tang Chengqi Zhang Zhenzhen Ju Shiyu Zheng Ziyue Wen Sunde Xu Yun Chen Zhonghua Ma 《Molecular Plant Pathology》2018,19(7):1595-1611
Deoxynivalenol (DON) is a mycotoxin produced in cereal crops infected with Fusarium graminearum. DON poses a serious threat to human and animal health, and is a critical virulence factor. Various environmental factors, including reactive oxygen species (ROS), have been shown to interfere with DON biosynthesis in this pathogen. The regulatory mechanisms of how ROS trigger DON production have been investigated extensively in F. graminearum. However, the role of the endogenous ROS‐generating system in DON biosynthesis is largely unknown. In this study, we genetically analysed the function of leucine zipper‐EF‐hand‐containing transmembrane 1 (LETM1) superfamily proteins and evaluated the role of the mitochondrial‐produced ROS in DON biosynthesis. Our results show that there are two Letm1 orthologues, FgLetm1 and FgLetm2, in F. graminearum. FgLetm1 is localized to the mitochondria and is essential for mitochondrial integrity, whereas FgLetm2 plays a minor role in the maintenance of mitochondrial integrity. The ΔFgLetm1 mutant demonstrated a vegetative growth defect, abnormal conidia and increased sensitivity to various stress agents. More importantly, the ΔFgLetm1 mutant showed significantly reduced levels of endogenous ROS, decreased DON biosynthesis and attenuated virulence in planta. To our knowledge, this is the first report showing that mitochondrial integrity and endogenous ROS production by mitochondria are important for DON production and virulence in Fusarium species. 相似文献
984.
Activation of PhoBR under phosphate‐rich conditions reduces the virulence of Xanthomonas oryzae pv. oryzae
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Dehong Zheng Bingbing Xue Yanan Shao Haoquan Yu Xiaoyan Yao Lifang Ruan 《Molecular Plant Pathology》2018,19(9):2066-2076
The two‐component signal transduction system PhoBR regulates the adaptation to phosphate limitation and the virulence of many animal bacterial pathogens. However, PhoBR in phytopathogens has rarely been investigated. In this study, we found that PhoBR in Xanthomonas oryzae pv. oryzae (Xoo), the pathogen of rice bacterial leaf blight, also regulates the adaptation to phosphate starvation. Unexpectedly, rice leaves infected by the phoBR‐deleted mutant and wild‐type PXO99A showed similar lesions, indicating that PhoBR is unnecessary for the virulence of Xoo. phoBR was found to be silenced during host infection, whereas artificially constitutive PhoBR expression attenuated virulence on host rice and growth in phosphate‐rich media. RNA‐sequencing (RNA‐seq) was then performed to investigate the global effect caused by constitutive PhoBR activation. RNA‐seq and further experiments revealed that the PhoBR regulon in Xoo comprised a wide range of genes. Nutrient transport and metabolism readjustments that resulted from PhoBR regulon activation may be responsible for growth attenuation. Our findings suggest that growth reduction regulated by PhoBR is a fitness cost of adaptation to phosphate starvation. PhoBR in Xoo is activated under phosphate‐limited conditions, which could exist in epiphytic and saprophytic surviving phases, and is strictly repressed within phosphate‐rich host plants to minimize fitness costs. 相似文献
985.
Unbiased random mutagenesis contributes to a better understanding of the virulent behaviour of Paenibacillus larvae
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Aims
American foulbrood, caused by the Gram‐positive bacteria Paenibacillus larvae, is one of the most severe bacterial diseases of the European honey bee. The bacterium has been known for long, but only the last decade the mechanisms used by the pathogen to cause disease in its host are starting to unravel. In this study, the knowledge of this virulent behaviour is expanded and several possible virulence factors are suggested.Methods and Results
Identification of possible virulence factors has been done by random mutagenesis to ensure an unbiased approach. A library of mutants was tested for a significant difference in virulence using in vitro exposure assays. Affected loci were characterized and their potential to contribute in virulence of the pathogen was assessed.Conclusions
The identified mutated loci dacB, dnaK, metN, ywqD, lysC, serC and gbpA are known to encode for virulence factors in other bacteria and are suggested to play a similar role in P. larvae.Significance and Impact of the Study
The study identified new possible virulence factors for P. larvae genotype ERIC I in an unbiased way. This contributes to the knowledge and understanding of the possible mechanisms used by this pathogen to colonize and kill its host. 相似文献986.
987.
988.
Saskia Lehr Juliane Vier Georg Häcker Susanne Kirschnek 《Microbes and infection / Institut Pasteur》2018,20(5):284-292
The obligate intracellular bacterium Chlamydia trachomatis is the most common bacterial agent of sexually transmitted disease world-wide. Chlamydia trachomatis primarily infects epithelial cells of the genital tract but the infection may be associated with ascending infection. Infection-associated inflammation can cause tissue damage resulting in female infertility and ectopic pregnancy. The precise mechanism of inflammatory tissue damage is unclear but earlier studies implicate the chlamydial cryptic plasmid as well as responding neutrophils. We here rebuilt the interaction of Chlamydia trachomatis-infected epithelial cells and neutrophils in-vitro. During infection of human (HeLa) or mouse (oviduct) epithelial cells with Chlamydia trachomatis, a soluble factor was produced that attracted neutrophils and prolonged neutrophil survival, independently of Toll-like receptor signaling but dependent on the chlamydial plasmid. A number of cytokines, but most strongly GM-CSF, were secreted at higher amounts from cells infected with plasmid-bearing, compared to plasmid-deficient, bacteria. Blocking GM-CSF removed the secreted pro-survival activity towards neutrophils. A second, neutrophil TNF-stimulatory activity was detected in supernatants, requiring MyD88 or TRIF independently of the plasmid. The results identify two pro-inflammatory activities generated during chlamydial infection of epithelial cells and suggest that the epithelial cell, partly through the chlamydial plasmid, can initiate a myeloid immune response and inflammation. 相似文献
989.
990.
Bacterial consortium volatile suspended soil (VSS) (Vatva soil sample) with a capability of azo dye Reactive Orange M2R (ROM2R) decolorization and degradation (shown in our earlier studies using Fourier transform infrared spectroscopy (FTIR) and phytotoxicity studies) was isolated from industrial wastewaters by enrichment culture technique. The present study was carried out to study bacterial population dynamics in consortium Vatva soil sample (VSS) during azo dye ROM2R degradation and to identify the consortium members that were actively involved in the degradation process. To achieve this goal, a real-time Polymerase chain reaction (PCR) assay targeting species-specific region of 16S rDNA of each consortial bacteria was developed to provide quantitative information about the bacterial abundance during azo dye degradation. The real-time PCR assay indicated that Pseudomonas aeruginosa (VSS-6) dominated consortium bacterial community during the active continuous bioremediation process. Attempt has been made to scale up from 100 ml volume to 10 L operation volume with intermittent additions (batch fed loadings) in a Sequence batch reactor (SBR). The development of VSS consortium biomass (MLVSS), changes in COD and biochemical oxygen demand, and the dye degradation were studied under conditions simulating the operations of biological effluent treatment in an attempt to develop a commercially applicable dye effluent treatment process unit. 相似文献