Genetics of Phytopathology: Phytopathogenic Bacteria. In: Esser K, Kadereit JW, Lüttge U, Runge M, editors. Progress in Botany. Berlin: Springer Berlin Heidelberg; 1999. pp. 119-38. [DOI: 10.1007/978-3-642-59940-8_5]

Polysaccharide Based Polymers Produced by Scabby Cankered Cactus Pear (Opuntia ficus-indica L.) Infected by Neofusicoccum batangarum: Composition, Structure, and Chemico-Physical Properties

Neofusiccocum batangarum is the causal agent of scabby canker of cactus pear (Opuntia ficus-indica L.). The symptoms of this disease are characterized by crusty, perennial cankers, with a leathery, brown halo. Characteristically, a viscous polysaccharide exudate, caking on contact with air, leaks from cankers and forms strips or cerebriform masses on the surface of cactus pear cladodes. When this polysaccharide mass was partial purified, surprisingly, generated a gel. The TLC analysis and the HPLC profile of methyl 2-(polyhydroxyalkyl)-3-(o-tolylthiocarbomoyl)-thiazolidine-4R-carboxylates obtained from the mixture of monosaccharides produced by acid hydrolysis of the three EPSs examined in this research work [the polysaccharide component of the exudate (EPSC) and the EPSs extracted from asymptomatic (EPSH) and symptomatic (EPSD) cladodes] showed the presence of d-galactose, l-rhamnose, and d-glucose in a 1:1:0.5 ratio in EPSC while d-galactose, l-rhamnose, d-glucose, and d-xylose at the same ratio were observed in EPSH and EPSD. The presence of uronic acid residues in EPSC was also showed by solid state NMR and IR investigation. Furthermore, this manuscript reports the chemical-physical characterization of the gel produced by the infected cactus pear.

Microbial exopolysaccharides: Synthesis pathways, types and their commercial applications

Polysaccharides are essential natural metabolites found in all life forms such as microorganisms, animals and plants with various biochemical structures and biological functions. Among all the life forms microbial exopolysaccharides are produced in shorter time duration as they responsible for the microbial cell adhesion and protection during unfavorable growth conditions. Microbial exopolysaccharides are composed of repeated sugar units of same or different types and form a complex by associating with proteins, lipids, metal ions, extracellular DNA (eDNA), organic and inorganic compounds to form a protective layer around the microbial colonies collectively known as biofilm. Specific functions of exopolysaccharides depend on structural composition and habitat of a host microorganism. There are various techniques to study the composition and structure of exopolysaccharides such as High Performance Anion Exchange Chromatography with Pulsed Amperometric Detection, Size Exclusion Chromatography coupled with multi-laser light scattering (SEC-MALLS),X-Ray diffraction (XRD), Differential Scanning Calorimetry (DSC), Fourier Transform Infrared (FTIR) and Thermal Gravimetric Analysis (TGA), etc. In the current article, we reviewed microbial exopolysaccharides physiochemical properties, composition, analyzing techniques through which possible commercial applications in dairy products, cosmetics, research, agriculture and petroleum industry can be performed.

Two thiadiazole compounds promote rice defence against Xanthomonas oryzae pv. oryzae by suppressing the bacterium's production of extracellular polysaccharides

Thiazole, isothiazole, thiadiazole, and their derivatives are used to control various human, animal and plant diseases. In addition to having direct anti-microbial and anti-fungal properties, these compounds are thought to induce host defences, but the mechanism of defence induction remains poorly understood. This article reports that the thiadiazoles of zinc thiazole and bismerthiazol induce H2 O2 accumulation, up-regulation of defence-related genes, callose deposition and hypersensitive response-like cell death in rice leaves infected with Xanthomonas oryaze pv. oryzae (Xoo) strain ZJ173, but not in non-infected leaves. These defence responses in Xoo-infected leaves were suppressed by the exogenous application of catalase, which reduces H2 O2 accumulation. The application of extracellular polysaccharides (EPSs) extracted from strain ZJ173 significantly compromised rice defence against ZJ173 with or without thiadiazole treatment. The EPS-deficient Xoo mutant ∆gumH triggered a stronger defence than its parent strain ZJ173. The thiadiazole treatments reduced EPS production by strain ZJ173, but not by the thiadiazole-resistant strain 2-1-1, which is thiadiazole resistant in vivo, but not in vitro; moreover, enhanced defence was not detected in thiadiazole-treated rice inoculated with 2-1-1. Based on these data, we infer that zinc thiazole and bismerthiazol promote rice defence against Xoo by inhibiting the production of bacterial EPS.

Exopolysaccharides produced by plant pathogenic bacteria affect ascorbate metabolism in Nicotiana tabacum

The role of the exopolysaccharides (EPSs) produced by plant pathogenic bacteria has not completely clarified, they are considered either molecules able to avoid or delay the activation of plant defences, or acting as signal in the plant-pathogen cross-talk. In order to understand whether EPSs are recognized by infected plant cells and are able to induce the activation of plant defence responses, their capability to induce metabolic alteration in tobacco cells has been analysed. The results indicate that several EPSs, even if not chemically related, induce increases in phenylalanine ammonia-lyase, a marker enzyme of defence responses of plants against stress; but others are completely ineffective. The EPSs affecting phenylalanine ammonia-lyase also induce an increase in hydrogen peroxide production. Moreover, they alter the metabolism of ascorbate, another parameter indicative of the presence of stress conditions and the involvement of which in the hypersensitive reaction has been recently reported. The possibility that specific EPSs could act as signals in the plant-pathogenic bacteria interaction is discussed.

Structural determination of the phytotoxic mannan exopolysaccharide from Pseudomonas syringae pv. ciccaronei

The structural determination was performed of a mannan exopolysaccharide from the gram negative bacterium Pseudomonas syringae pv. ciccaronei, which is the pathogenic agent responsible for the leaf spots of carob plants. The structure, obtained by chemical, enzymatic and spectroscopic methods, consisted of a backbone of alpha-(1-->6)-linked mannopyranose units with 80% substituted at C-2 by mono-, di- and trisaccharide side chains. In addition, terminal glucose units and phosphate groups were found to be present. This is, to the best of our knowledge, the first report of a mannan exopolysaccharide structure from a phytopathogenic bacterium. The pure polysaccharide showed phytotoxic effects, i.e., chlorosis and necrosis on tobacco leaves.