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Scientific Reports Jan 2016Osmoregulated periplasmic glucans (OPGs) are a family of periplasmic oligosaccharides found in the envelope of most Proteobacteria. They are required for virulence of...
Osmoregulated periplasmic glucans (OPGs) are a family of periplasmic oligosaccharides found in the envelope of most Proteobacteria. They are required for virulence of zoo- and phyto-pathogens. The glucose backbone of OPGs is substituted by various kinds of molecules depending on the species, O-succinyl residues being the most widely distributed. In our model, Dickeya dadantii, a phytopathogenic bacteria causing soft rot disease in a wide range of plant species, the backbone of OPGs is substituted by O-succinyl residues in media of high osmolarity and by O-acetyl residues whatever the osmolarity. The opgC gene encoding a transmembrane protein required for the succinylation of the OPGs in D. dadantii was found after an in silico search of a gene encoding a protein with the main characteristics recovered in the two previously characterized OpgC of E. coli and R. sphaeroides, i.e. 10 transmembrane segments and one acyl-transferase domain. Characterization of the opgC gene revealed that high osmolarity expression of the succinyl transferase is controlled by both the EnvZ-OmpR and RcsCDB phosphorelay systems. The loss of O-succinyl residue did not affect the virulence of D. dadantii, suggesting that only the glucose backbone of OPGs is required for virulence.
Topics: Bacterial Proteins; Enterobacteriaceae; Escherichia coli; Gene Order; Genetic Complementation Test; Genome, Bacterial; Glucans; Osmolar Concentration; Osmoregulation; Periplasm; Phosphorylation; Promoter Regions, Genetic; Protein Binding; Virulence
PubMed: 26790533
DOI: 10.1038/srep19619 -
The Plant Journal : For Cell and... Apr 2015Transcriptome analysis of bacterial pathogens is a powerful approach to identify and study the expression patterns of genes during host infection. However, analysis of...
Transcriptome analysis of bacterial pathogens is a powerful approach to identify and study the expression patterns of genes during host infection. However, analysis of the early stages of bacterial virulence at the genome scale is lacking with respect to understanding of plant-pathogen interactions and diseases, especially during foliar infection. This is mainly due to both the low ratio of bacterial cells to plant material at the beginning of infection, and the high contamination by chloroplastic material. Here we describe a reliable and straightforward method for bacterial cell purification from infected leaf tissues, effective even if only a small amount of bacteria is present relative to plant material. The efficiency of this method for transcriptomic analysis was validated by analysing the expression profiles of the phytopathogenic enterobacterium Dickeya dadantii, a soft rot disease-causing agent, during the first hours of infection of the model host plant Arabidopsis thaliana. Transcriptome profiles of epiphytic bacteria and bacteria colonizing host tissues were compared, allowing identification of approximately 100 differentially expressed genes. Requiring no specific equipment, cost-friendly and easily transferable to other pathosystems, this method should be of great interest for many other plant-bacteria interaction studies.
Topics: Arabidopsis; Enterobacteriaceae; Gene Expression Profiling; Gene Expression Regulation, Bacterial; Plant Diseases; Virulence
PubMed: 25740271
DOI: 10.1111/tpj.12812 -
Molecules (Basel, Switzerland) Jun 2019Bacterial stem and root rot disease of sweet potato caused by recently broke out in major sweet potato planting areas in China and calls for effective approaches to...
Bacterial stem and root rot disease of sweet potato caused by recently broke out in major sweet potato planting areas in China and calls for effective approaches to control the pathogen and disease. Here, we developed a simple method for green synthesis of silver nanoparticles (AgNPs) using bacterial culture supernatants. AgNPs synthesized with the cell-free culture supernatant of a bacterium displayed the characteristic surface plasmon resonance peak at 420-430 nm and as nanocrystallites in diameters of 20-100 nm determined by transmission electron microscopy, scanning electron microscopy, and X-ray diffraction spectroscopy. Functional groups associated with proteins in the culture supernatant may reduce silver ions and stabilize AgNPs. The AgNPs showed antibacterial activities against growth, swimming motility, biofilm formation, and maceration of sweet potato tubers whereas the culture supernatant of did not. AgNPs (12 µg∙ml) and AgNO (50 µg∙ml) showed close antibacterial activities. The antibacterial activities increased with the increase of AgNP concentrations. The green-synthesized AgNPs can be used to control the soft rot disease by control of pathogen contamination of sweet potato seed tubers.
Topics: Anti-Bacterial Agents; China; Culture Media; Enterobacteriaceae; Green Chemistry Technology; Metal Nanoparticles; Microbial Sensitivity Tests; Microscopy, Electron, Scanning; Microscopy, Electron, Transmission; Pseudomonas; Silver; Spectroscopy, Fourier Transform Infrared; Surface Plasmon Resonance
PubMed: 31234369
DOI: 10.3390/molecules24122303 -
Plant Disease Jun 2015Postharvest soft rots of sweetpotato caused by Rhizopus stolonifer (Rhizopus soft rot) and Dickeya dadantii (bacterial root rot) occur sporadically and can result in...
Postharvest soft rots of sweetpotato caused by Rhizopus stolonifer (Rhizopus soft rot) and Dickeya dadantii (bacterial root rot) occur sporadically and can result in significant losses. A 3-year field study related preharvest conditions, including soil texture, chemistry, and fertility; air temperature; soil temperature and moisture; and various cultural practices (153 total variables), to postharvest susceptibility to both diseases in 75 sweetpotato fields in North Carolina and 63 sweetpotato fields in Louisiana. Storage roots were sampled from each field, cured, stored, and inoculated with each pathogen after 100 to 120 days in storage. Disease susceptibility was measured as incidence of diseased storage roots 10 days following inoculation. There was wide variation from field to field in incidence of both diseases (0 to 100% for Rhizopus soft rot and 5 to 95% for bacterial root rot) in both states in each year. Correlations between disease incidence and each of the preharvest variables revealed numerous significant correlations but the variables that correlated with disease incidence were different between North Carolina and Louisiana. Models for both diseases were built by first using forward stepwise regression to identify variables of interest, followed by a mixed-model analysis to produce a final reduced model. For North Carolina fields, postharvest Rhizopus soft rot susceptibility was described by the percentage of the soil cation exchange capacity occupied by calcium, amount of plant-available soil phosphorus, percent soil humic matter, mean air temperature, mean volumetric soil moisture at 40 cm in depth, and mean soil temperature at 2 cm in depth. Postharvest bacterial soft rot susceptibility was described by soil pH and the number of days of high soil temperature late in the season. For Louisiana fields, Rhizopus soft rot susceptibility was described by a complex of variables, including late-season air and soil temperature and late-season days of extreme soil moisture. For bacterial root rot, days of low air temperature and days of high soil temperature late in the season as well as days of low soil moisture best described variation. Although the influence of preharvest variables on postharvest susceptibility was profound for each disease, the complexity of factors involved and differences between the data for the two states makes development of a predictive system extremely difficult.
PubMed: 30699536
DOI: 10.1094/PDIS-11-14-1143-RE -
International Journal of Systematic and... Sep 2016Gram-stain-negative, pectinolytic bacteria were repeatedly isolated from pear trees displaying symptoms of bleeding canker in China. Three strains, JS5T, LN1 and QZH3,...
Gram-stain-negative, pectinolytic bacteria were repeatedly isolated from pear trees displaying symptoms of bleeding canker in China. Three strains, JS5T, LN1 and QZH3, had identical 16S rRNA gene sequences that shared 99 % similarity to the type strain of Dickeya dadantii. Phylogenetic analysis of strains JS5T, LN1 and QZH3 with isolates representing all species of the genus Dickeya and related Pectobacterium species supported their affiliation to Dickeya. Multi-locus sequence typing employing concatenated sequences encoding recA, fusA, gapA, purA, rplB, dnaX and the intergenic spacer illustrated a phylogeny which placed strains JS5T, LN1 and QZH3 as a distinct clade, separate from all other species of the genus Dickeya. Average nucleotide identity values obtained in comparison with all species of the genus Dickeya supported the distinctiveness of strain JS5T within the genus Dickeya. Additionally, all three strains were phenotypically distinguished from other species of the genus Dickeya by failing to hydrolyse casein, and by producing acids from (-)-d-arabinose, (+)melibiose, (+)raffinose, mannitol and myo-inositol, but not from 5-keto-d-gluconate or β-gentiobiose. The name Dickeya fangzhongdai sp. nov. is proposed to accommodate these strains; the type strain is JS5T (=CGMCC 1.15464T=DSM 101947T).
Topics: Bacterial Typing Techniques; China; DNA, Bacterial; Enterobacteriaceae; Fatty Acids; Genes, Bacterial; Multilocus Sequence Typing; Phenotype; Phylogeny; Plant Diseases; Pyrus; RNA, Ribosomal, 16S; Sequence Analysis, DNA
PubMed: 27045848
DOI: 10.1099/ijsem.0.001060 -
Molecular Plant Pathology Feb 2018Soft-rot diseases of plants attributed to Dickeya dadantii result from lysis of the plant cell wall caused by pectic enzymes released by the bacterial cell by a type II...
Soft-rot diseases of plants attributed to Dickeya dadantii result from lysis of the plant cell wall caused by pectic enzymes released by the bacterial cell by a type II secretion system (T2SS). Arabidopsis thaliana can express several lines of defence against this bacterium. We employed bacterial mutants with defective envelope structures or secreted proteins to examine early plant defence reactions. We focused on the production of AtrbohD-dependent reactive oxygen species (ROS), callose deposition and cell death as indicators of these reactions. We observed a significant reduction in ROS and callose formation with a bacterial mutant in which genes encoding five pectate lyases (Pels) were disrupted. Treatment of plant leaves with bacterial culture filtrates containing Pels resulted in ROS and callose production, and both reactions were dependent on a functional AtrbohD gene. ROS and callose were produced in response to treatment with a cellular fraction of a T2SS-negative mutant grown in a Pels-inducing medium. Finally, ROS and callose were produced in leaves treated with purified Pels that had also been shown to induce the expression of jasmonic acid-dependent defence genes. Pel catalytic activity is required for the induction of ROS accumulation. In contrast, cell death observed in leaves infected with the wild-type strain appeared to be independent of a functional AtrbohD gene. It was also independent of the bacterial production of pectic enzymes and the type III secretion system (T3SS). In conclusion, the work presented here shows that D. dadantii is recognized by the A. thaliana innate immune system through the action of pectic enzymes secreted by bacteria at the site of infection. This recognition leads to AtrbohD-dependent ROS and callose accumulation, but not cell death.
Topics: Arabidopsis; Gammaproteobacteria; Glucans; Immunity, Innate; Oligosaccharides; Polysaccharide-Lyases; Reactive Oxygen Species; Type III Secretion Systems; Virulence
PubMed: 27925401
DOI: 10.1111/mpp.12522 -
Journal of Bacteriology Jul 2023The transcriptional regulator PecS is encoded by select bacterial pathogens. For instance, in the plant pathogen Dickeya dadantii, PecS controls a range of virulence...
The transcriptional regulator PecS is encoded by select bacterial pathogens. For instance, in the plant pathogen Dickeya dadantii, PecS controls a range of virulence genes, including pectinase genes and the divergently oriented gene , which encodes an efflux pump through which the antioxidant indigoidine is exported. In the plant pathogen (formerly named Agrobacterium tumefaciens), the locus is conserved. Using a strain of in which has been disrupted, we show here that PecS controls a range of phenotypes that are associated with bacterial fitness. PecS represses flagellar motility and chemotaxis, which are processes that are important for to reach plant wound sites. Biofilm formation and microaerobic survival are reduced in the disruption strain, whereas the production of acyl homoserine lactone (AHL) and resistance to reactive oxygen species (ROS) are increased when is disrupted. AHL production and resistance to ROS are expected to be particularly relevant in the host environment. We also show that PecS does not participate in the induction of genes. The inducing ligands for PecS, urate, and xanthine, may be found in the rhizosphere, and they accumulate within the plant host upon infection. Therefore, our data suggest that PecS mediates fitness during its transition from the rhizosphere to the host plant. PecS is a transcription factor that is conserved in several pathogenic bacteria, where it regulates virulence genes. The plant pathogen is important not only for its induction of crown galls in susceptible plants but also for its role as a tool in the genetic manipulation of host plants. We show here that PecS controls a range of phenotypes, which would confer the bacteria an advantage while transitioning from the rhizosphere to the host plant. This includes the production of signaling molecules, which are critical for the propagation of the tumor-inducing plasmid. A more complete understanding of the infection process may inform approaches by which to treat infections as well as to facilitate the transformation of recalcitrant plant species.
Topics: Transcription Factors; Reactive Oxygen Species; Gene Expression Regulation, Bacterial; Agrobacterium; Agrobacterium tumefaciens; Bacterial Proteins
PubMed: 37314346
DOI: 10.1128/jb.00478-22 -
Molecular Plant Pathology Feb 2015The type III secretion system (T3SS) is a major virulence factor in many Gram-negative bacterial pathogens and represents a particularly appealing target for...
The type III secretion system (T3SS) is a major virulence factor in many Gram-negative bacterial pathogens and represents a particularly appealing target for antimicrobial agents. Previous studies have shown that the plant phenolic compound p-coumaric acid (PCA) plays a role in the inhibition of T3SS expression of the phytopathogen Dickeya dadantii 3937. This study screened a series of derivatives of plant phenolic compounds and identified that trans-4-hydroxycinnamohydroxamic acid (TS103) has an eight-fold higher inhibitory potency than PCA on the T3SS of D. dadantii. The effect of TS103 on regulatory components of the T3SS was further elucidated. Our results suggest that TS103 inhibits HrpY phosphorylation and leads to reduced levels of hrpS and hrpL transcripts. In addition, through a reduction in the RNA levels of the regulatory small RNA RsmB, TS103 also inhibits hrpL at the post-transcriptional level via the rsmB-RsmA regulatory pathway. Finally, TS103 inhibits hrpL transcription and mRNA stability, which leads to reduced expression of HrpL regulon genes, such as hrpA and hrpN. To our knowledge, this is the first inhibitor to affect the T3SS through both the transcriptional and post-transcriptional pathways in the soft-rot phytopathogen D. dadantii 3937.
Topics: Enterobacteriaceae; Escherichia coli Proteins; Phenols; Signal Transduction
PubMed: 24986378
DOI: 10.1111/mpp.12168 -
Polymers Jul 2022In order to obtain a thermostable pectate lyase for ramie degumming, a rational design based on structural analysis was carried out on a novel pectate lyase (Pel419)...
In order to obtain a thermostable pectate lyase for ramie degumming, a rational design based on structural analysis was carried out on a novel pectate lyase (Pel419) derived from the DCE-01 for high-efficiency ramie degumming. A total of five potential amino acid sites were chosen to replace residues. Then, the mutant enzymes were subjected to the heterologous expressions in and their enzymatic characteristics were determined. The optimal reaction temperature for the five mutants kept consistent with that for the wild type. The enzyme activity and thermal stability of mutant V52A were significantly improved. Meanwhile, the weight loss rate obtained by V52A with the best enzymatic characteristics in the ramie degumming process at 50 °C is comparable with that obtained by commercial cotton-ramie processing pectinases, indicating that V52A was a potential industrial enzyme that could be applied to large-scale ramie degumming. In this study, the biological functions of conservative residues of Pel419 were preliminarily explored. The mutant V52A with both enzymatic activity and improved heat resistance was acquired, providing a superior material for developing enzyme preparations of ramie degumming, and rendering an effective method for the rational design aiming to improve the thermostability of pectate lyase.
PubMed: 35890653
DOI: 10.3390/polym14142878 -
Molecular Plant Pathology Jun 2015Dickeya dadantii is a plant-pathogenic enterobacterium responsible for plant soft rot disease in a wide range of hosts, including the model plant Arabidopsis thaliana....
Dickeya dadantii is a plant-pathogenic enterobacterium responsible for plant soft rot disease in a wide range of hosts, including the model plant Arabidopsis thaliana. Iron distribution in infected A. thaliana was investigated at the cellular scale using the Perls'-diaminobenzidine-H2 O2 (PDH) method. Iron visualization during infection reveals a loss of iron from cellular compartments and plant cell walls. During symptom progression, two distinct zones are clearly visible: a macerated zone displaying weak iron content and a healthy zone displaying strong iron content. Immunolabelling of cell wall methylated pectin shows that pectin degradation is correlated with iron release from cell walls, indicating a strong relationship between cell wall integrity and iron in plant tissues. Using a D. dadantii lipopolysaccharide antibody, we show that bacteria are restricted to the infected tissue, and that they accumulate iron in planta. In conclusion, weak iron content is strictly correlated with bacterial cell localization in the infected tissues, indicating a crucial role of this element during the interaction. This is the first report of iron localization at the cellular level during a plant-microbe interaction and shows that PDH is a method of choice in this type of investigation.
Topics: Arabidopsis; Cell Wall; Enterobacteriaceae; Ferritins; Iron; Plant Diseases; Plant Leaves; Protein Transport
PubMed: 25266463
DOI: 10.1111/mpp.12208