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Environmental Microbiology Reports Oct 2015This review emphasizes the biological roles of the osmoregulated periplasmic glucans (OPGs). Osmoregulated periplasmic glucans occur in almost all α-, β- and... (Review)
Review
This review emphasizes the biological roles of the osmoregulated periplasmic glucans (OPGs). Osmoregulated periplasmic glucans occur in almost all α-, β- and γ-Proteobacteria. This polymer of glucose is required for full virulence. The roles of the OPGs are complex and vary depending on the species. Here, we outline the four major roles of the OPGs through four different pathogenic and one symbiotic bacterial models (Dickeya dadantii, Salmonella enterica, Pseudomonas aeruginosa, Brucella abortus and Sinorhizobium meliloti). When periplasmic, the OPGs are a part of the signal transduction pathway and indirectly regulate genes involved in virulence. The OPGs can also be secreted. When outside of the cell, they interact directly with antibiotics to protect the bacterial cell or interact with the host cell to facilitate the invasion process. When OPGs are not found, as in the ε-Proteobacteria, OPG-like oligosaccharides are present. Their presence strengthens the evidence that OPGs play an important role in virulence.
Topics: Alphaproteobacteria; Anti-Bacterial Agents; Gammaproteobacteria; Glucans; Osmoregulation; Periplasm; Signal Transduction; Virulence
PubMed: 26265506
DOI: 10.1111/1758-2229.12325 -
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 -
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 -
International Journal of Molecular... Jun 2021Coumarins belong to a group of secondary metabolites well known for their high biological activities including antibacterial and antifungal properties. Recently, an...
Coumarins belong to a group of secondary metabolites well known for their high biological activities including antibacterial and antifungal properties. Recently, an important role of coumarins in plant resistance to pathogens and their release into the rhizosphere upon pathogen infection was discovered. It is also well documented that coumarins play a crucial role in the growth under Fe-limited conditions. However, the mechanisms underlying interplay between plant resistance, accumulation of coumarins and Fe status, remain largely unknown. In this work, we investigated the effect of both mentioned factors on the disease severity using the model system of Arabidopsis/ spp. molecular interactions. We evaluated the disease symptoms in Arabidopsis plants, wild-type Col-0 and its mutants defective in coumarin accumulation, grown in hydroponic cultures with contrasting Fe regimes and in soil mixes. Under all tested conditions, Arabidopsis plants inoculated with IFB0099 strain developed more severe disease symptoms compared to lines inoculated with 3937. We also showed that the expression of genes encoding plant stress markers were strongly affected by IFB0099 infection. Interestingly, the response of plants to 3937 infection was genotype-dependent in Fe-deficient hydroponic solution.
Topics: Arabidopsis; Coumarins; Dickeya; Disease Resistance; Disease Susceptibility; Hydroponics; Iron; Plant Diseases; Plant Leaves; Plants; Stress, Physiological
PubMed: 34208600
DOI: 10.3390/ijms22126449 -
Pathogens (Basel, Switzerland) Dec 2020Copper nanoparticles (CuNPs) can offer an alternative to conventional copper bactericides and possibly slow down the development of bacterial resistance. This will...
Copper nanoparticles (CuNPs) can offer an alternative to conventional copper bactericides and possibly slow down the development of bacterial resistance. This will consequently lower the accumulation rate of copper to soil and water and lower the environmental and health burden imposed by copper application. Physical and chemical methods have been reported to synthesize CuNPs but their use as bactericides in plants has been understudied. In this study, two different CuNPs products have been developed, CuNP1 and CuNP2 in two respective concentrations (1500 ppm or 300 ppm). Both products were characterized using Dynamic Light Scattering, Transmission Electron Microscopy, Attenuated Total Reflection measurements, X-ray Photoelectron Spectroscopy, X-ray Diffraction and Scattering, and Laser Doppler Electrophoresis. They were evaluated for their antibacterial efficacy in vitro against the gram-negative species , , , , , pv. , and pv. . Evaluation was based on comparisons with two commercial bactericides: Kocide (copper hydroxide) and Nordox (copper oxide). CuNP1 inhibited the growth of five species, restrained the growth of and had no effect in pv . MICs were significantly lower than those of the commercial formulations. CuNP2 inhibited the growth of and restrained growth of pv. . Again, its overall activity was higher compared to commercial formulations. An extensive in vitro evaluation of CuNPs that show higher potential compared to their conventional counterpart is reported for the first time and suggests that synthesis of stable CuNPs can lead to the development of low-cost sustainable commercial products.
PubMed: 33291381
DOI: 10.3390/pathogens9121024 -
RNA (New York, N.Y.) Apr 2017Regulation of gene expression by encoded riboswitches is a prevalent theme in bacteria. Of the hundreds of riboswitch families identified, the majority of them remain as...
Regulation of gene expression by encoded riboswitches is a prevalent theme in bacteria. Of the hundreds of riboswitch families identified, the majority of them remain as orphans, without a clear ligand assignment. The orphan family was recently characterized as guanidine-sensing riboswitches. Herein we present a 2.3 Å crystal structure of the guanidine-bound riboswitch from The riboswitch folds into a boot-shaped structure, with a coaxially stacked P1/P2 stem forming the boot, and a 3'-P3 stem-loop forming the heel. Sophisticated base-pairing and cross-helix tertiary contacts give rise to the ligand-binding pocket between the boot and the heel. The guanidine is recognized in its positively charged guanidinium form, in its sp hybridization state, through a network of coplanar hydrogen bonds and by a cation-π stacking contact on top of a conserved guanosine residue. Disruption of these contacts resulted in severe guanidinium-binding defects. These results provide the structural basis for specific guanidine sensing by riboswitches and pave the way for a deeper understanding of guanidine detoxification-a previously unappreciated aspect of bacterial physiology.
Topics: Base Pairing; Binding Sites; Crystallography, X-Ray; Enterobacteriaceae; Guanidine; Hydrogen Bonding; Ligands; Models, Molecular; Nucleic Acid Conformation; RNA, Bacterial; Riboswitch; Static Electricity; Thermodynamics
PubMed: 28096518
DOI: 10.1261/rna.060186.116 -
The Journal of Biological Chemistry Feb 2019In the quest for a sustainable economy of the Earth's resources and for renewable sources of energy, a promising avenue is to exploit the vast quantity of polysaccharide...
In the quest for a sustainable economy of the Earth's resources and for renewable sources of energy, a promising avenue is to exploit the vast quantity of polysaccharide molecules contained in green wastes. To that end, the decomposition of pectin appears to be an interesting target because this polymeric carbohydrate is abundant in many fruit pulps and soft vegetables. To quantitatively study this degradation process, here we designed a bioreactor that is continuously fed with de-esterified pectin (PGA). Thanks to the pectate lyases produced by bacteria cultivated in the vessel, the PGA is depolymerized into oligogalacturonates (UGA), which are continuously extracted from the tank. A mathematical model of our system predicted that the conversion efficiency of PGA into UGA increases in a range of coefficients of dilution until reaching an upper limit where the fraction of UGA that is extracted from the bioreactor is maximized. Results from experiments with a continuous reactor hosting a strain of the plant pathogenic bacterium and in which the dilution coefficients were varied quantitatively validated the predictions of our model. A further theoretical analysis of the system enabled an comparison of the efficiency of eight other pectate lyase-producing microorganisms with that of Our findings suggest that is the most efficient microorganism and therefore the best candidate for a practical implementation of our scheme for the bioproduction of UGA from PGA.
Topics: Bacterial Proteins; Bioreactors; Enterobacteriaceae; Models, Biological; Oligosaccharides; Pectins; Polysaccharide-Lyases; Polysaccharides; Virulence Factors
PubMed: 30510137
DOI: 10.1074/jbc.RA118.004615 -
Nature Communications Oct 2019Few secreted proteins involved in plant infection common to necrotrophic bacteria, fungi and oomycetes have been identified except for plant cell wall-degrading enzymes....
Few secreted proteins involved in plant infection common to necrotrophic bacteria, fungi and oomycetes have been identified except for plant cell wall-degrading enzymes. Here we study a family of iron-binding proteins that is present in Gram-negative and Gram-positive bacteria, fungi, oomycetes and some animals. Homolog proteins in the phytopathogenic bacterium Dickeya dadantii (IbpS) and the fungal necrotroph Botrytis cinerea (BcIbp) are involved in plant infection. IbpS is secreted, can bind iron and copper, and protects the bacteria against HO-induced death. Its 1.7 Å crystal structure reveals a classical Venus Fly trap fold that forms dimers in solution and in the crystal. We propose that secreted Ibp proteins binds exogenous metals and thus limit intracellular metal accumulation and ROS formation in the microorganisms.
Topics: Anti-Infective Agents, Local; Arabidopsis; Arabidopsis Proteins; Botrytis; Carrier Proteins; Copper; Defensins; Dickeya; Dimerization; Gammaproteobacteria; Hydrogen Peroxide; Iron; Iron-Binding Proteins; Plant Diseases; Reactive Oxygen Species; Siderophores
PubMed: 31649262
DOI: 10.1038/s41467-019-12826-x -
Frontiers in Microbiology 2015Random transposon mutagenesis is a powerful technique used to generate libraries of genetic insertions in many different bacterial strains. Here we develop a system...
Random transposon mutagenesis is a powerful technique used to generate libraries of genetic insertions in many different bacterial strains. Here we develop a system facilitating random transposon mutagenesis in a range of different Gram-negative bacterial strains, including Pectobacterium atrosepticum, Citrobacter rodentium, Serratia sp. ATCC39006, Serratia plymuthica, Dickeya dadantii, and many more. Transposon mutagenesis was optimized in each of these strains and three studies are presented to show the efficacy of this system. Firstly, the important agricultural pathogen D. dadantii was mutagenized. Two mutants that showed reduced protease production and one mutant producing the previously cryptic pigment, indigoidine, were identified and characterized. Secondly, the enterobacterium, Serratia sp. ATCC39006 was mutagenized and mutants incapable of producing gas vesicles, proteinaceous intracellular organelles, were identified. One of these contained a β-galactosidase transcriptional fusion within the gene gvpA1, essential for gas vesicle production. Finally, the system was used to mutate the biosynthetic gene clusters of the antifungal, anti-oomycete and anticancer polyketide, oocydin A, in the plant-associated enterobacterium, Dickeya solani MK10. The mutagenesis system was developed to allow easy identification of transposon insertion sites by sequencing, after facile generation of a replicon encompassing the transposon and adjacent DNA, post-excision. Furthermore, the system can also create transcriptional fusions with either β-galactosidase or β-glucuronidase as reporters, and exploits a variety of drug resistance markers so that multiple selectable fusions can be generated in a single strain. This system of various transposons has wide utility and can be combined in many different ways.
PubMed: 26733980
DOI: 10.3389/fmicb.2015.01442 -
PLoS Pathogens Aug 2019Necrotrophic plant pathogens acquire nutrients from dead plant cells, which requires the disintegration of the plant cell wall and tissue structures by the pathogen....
Necrotrophic plant pathogens acquire nutrients from dead plant cells, which requires the disintegration of the plant cell wall and tissue structures by the pathogen. Infected plants lose tissue integrity and functional immunity as a result, exposing the nutrient rich, decayed tissues to the environment. One challenge for the necrotrophs to successfully cause secondary infection (infection spread from an initially infected plant to the nearby uninfected plants) is to effectively utilize nutrients released from hosts towards building up a large population before other saprophytes come. In this study, we observed that the necrotrophic pathogen Dickeya dadantii exhibited heterogeneity in bacterial cell length in an isogenic population during infection of potato tuber. While some cells were regular rod-shape (<10μm), the rest elongated into filamentous cells (>10μm). Short cells tended to occur at the interface of healthy and diseased tissues, during the early stage of infection when active attacking and killing is occurring, while filamentous cells tended to form at a later stage of infection. Short cells expressed all necessary virulence factors and motility, whereas filamentous cells did not engage in virulence, were non-mobile and more sensitive to environmental stress. However, compared to the short cells, the filamentous cells displayed upregulated metabolic genes and increased growth, which may benefit the pathogens to build up a large population necessary for the secondary infection. The segregation of the two subpopulations was dependent on differential production of the alarmone guanosine tetraphosphate (ppGpp). When exposed to fresh tuber tissues or freestanding water, filamentous cells quickly transformed to short virulent cells. The pathogen adaptation of cell length heterogeneity identified in this study presents a model for how some necrotrophs balance virulence and vegetative growth to maximize fitness during infection.
Topics: Bacterial Proteins; Cell Wall; Enterobacteriaceae; Gene Expression Regulation, Bacterial; Guanosine Tetraphosphate; Host-Pathogen Interactions; Plant Diseases; Solanum tuberosum; Virulence; Virulence Factors
PubMed: 31381590
DOI: 10.1371/journal.ppat.1007703