The Potential of Cold Atmospheric Pressure Plasmas for the Direct Degradation of Organic Pollutants Derived from the Food Production Industry.

Specialized chemicals are used for intensifying food production, including boosting meat and crop yields. Among the applied formulations, antibiotics and pesticides pose a severe threat to the natural balance of the ecosystem, as they either contribute to the development of multidrug resistance among pathogens or exhibit ecotoxic and mutagenic actions of a persistent character. Recently, cold atmospheric pressure plasmas (CAPPs) have emerged as promising technologies for degradation of these organic pollutants. CAPP-based technologies show eco-friendliness and potency for the removal of organic pollutants of diverse chemical formulas and different modes of action. For this reason, various types of CAPP-based systems are presented in this review and assessed in terms of their constructions, types of discharges, operating parameters, and efficiencies in the degradation of antibiotics and persistent organic pollutants. Additionally, the key role of reactive oxygen and nitrogen species (RONS) is highlighted. Moreover, optimization of the CAPP operating parameters seems crucial to effectively remove contaminants. Finally, the CAPP-related paths and technologies are further considered in terms of biological and environmental effects associated with the treatments, including changes in antibacterial properties and toxicity of the exposed solutions, as well as the potential of the CAPP-based strategies for limiting the spread of multidrug resistance.

Heterogenicity within the LPS Structure in Relation to the Chosen Genomic and Physiological Features of the Plant Pathogen Pectobacterium parmentieri.

Pectobacterium parmentieri is a pectinolytic plant pathogenic bacterium causing high economic losses of cultivated plants. The highly devastating potential of this phytopathogen results from the efficient production of plant cell wall-degrading enzymes, i.e., pectinases, cellulases and proteases, in addition to the impact of accessory virulence factors such as motility, siderophores, biofilm and lipopolysaccharide (LPS). LPS belongs to pathogen-associated molecular patterns (PAMPs) and plays an important role in plant colonization and interaction with the defense systems of the host. Therefore, we decided to investigate the heterogeneity of O-polysaccharides (OPS) of LPS of different strains of P. parmentieri, in search of an association between the selected genomic and phenotypic features of the strains that share an identical structure of the OPS molecule. In the current study, OPS were isolated from the LPS of two P. parmentieri strains obtained either in Finland in the 1980s (SCC3193) or in Poland in 2013 (IFB5432). The purified polysaccharides were analyzed by utilizing 1D and 2D NMR spectroscopy (1H, DQF-COSY, TOCSY, ROESY, HSQC, HSQC-TOCSY and HMBC) in addition to chemical methods. Sugar and methylation analyses of native polysaccharides, absolute configuration assignment of constituent monosaccharides and NMR spectroscopy data revealed that these two P. parmentieri strains isolated in different countries possess the same structure of OPS with a very rare residue of 5,7-diamino-3,5,7,9-tetradeoxy-l-glycero-l-manno-non-2-ulosonic acid (pseudaminic acid) substituted in the position C-8: →3)-ß-d-Galf-(1→3)-α-d-Galp-(1→8)-ß-Pse4Ac5Ac7Ac-(2→6)-α-d-Glcp-(1→6)-ß-d-Glcp-(1→. The previous study indicated that three other P. parmentieri strains, namely IFB5427, IFB5408 and IFB5443, exhibit a different OPS molecule than SCC3193 and IFB5432. The conducted biodiversity-oriented assays revealed that the P. parmentieri IFB5427 and IFB5408 strains possessing the same OPS structure yielded the highest genome-wide similarity, according to average nucleotide identity analyses, in addition to the greatest ability to macerate chicory tissue among the studied P. parmentieri strains. The current research demonstrated a novel OPS structure, characteristic of at least two P. parmentieri strains (SCC3193 and IFB5432), and discussed the observed heterogenicity in the OPS of P. parmentieri in a broad genomic and phenotype-related context.

Multivariate Optimization of the FLC-dc-APGD-Based Reaction-Discharge System for Continuous Production of a Plasma-Activated Liquid of Defined Physicochemical and Anti-Phytopathogenic Properties.

To the present day, no efficient plant protection method against economically important bacterial phytopathogens from the Pectobacteriaceae family has been implemented into agricultural practice. In this view, we have performed a multivariate optimization of the operating parameters of the reaction-discharge system, employing direct current atmospheric pressure glow discharge, generated in contact with a flowing liquid cathode (FLC-dc-APGD), for the production of a plasma-activated liquid (PAL) of defined physicochemical and anti-phytopathogenic properties. As a result, the effect of the operating parameters on the conductivity of PAL acquired under these conditions was assessed. The revealed optimal operating conditions, under which the PAL of the highest conductivity was obtained, were as follows: flow rate of the solution equaled 2.0 mL min-1, the discharge current was 30 mA, and the inorganic salt concentration (ammonium nitrate, NH4NO3) in the solution turned out to be 0.50% (m/w). The developed PAL exhibited bacteriostatic and bactericidal properties toward Dickeya solani IFB0099 and Pectobacterium atrosepticum IFB5103 strains, with minimal inhibitory and minimal bactericidal concentrations equaling 25%. After 24 h exposure to 25% PAL, 100% (1-2 × 106) of D. solani and P. atrosepticum cells lost viability. We attributed the antibacterial properties of PAL to the presence of deeply penetrating, reactive oxygen and nitrogen species (RONS), which were, in this case, OH, O, O3, H2O2, HO2, NH, N2, N2+, NO2-, NO3-, and NH4+. Putatively, the generated low-cost, eco-friendly, easy-to-store, and transport PAL, exhibiting the required antibacterial and physicochemical properties, may find numerous applications in the plant protection sector.

Implementation of a Non-Thermal Atmospheric Pressure Plasma for Eradication of Plant Pathogens from a Surface of Economically Important Seeds.

Plant pathogenic bacteria cause significant economic losses in the global food production sector. To secure an adequate amount of high-quality nutrition for the growing human population, novel approaches need to be undertaken to combat plant disease-causing agents. As the currently available methods to eliminate bacterial phytopathogens are scarce, we evaluated the effectiveness and mechanism of action of a non-thermal atmospheric pressure plasma (NTAPP). It was ignited from a dielectric barrier discharge (DBD) operation in a plasma pencil, and applied for the first time for eradication of Dickeya and Pectobacterium spp., inoculated either on glass spheres or mung bean seeds. Furthermore, the impact of the DBD exposure on mung bean seeds germination and seedlings growth was estimated. The observed bacterial inactivation rates exceeded 3.07 logs. The two-minute DBD exposure stimulated by 3-4% the germination rate of mung bean seeds and by 13.4% subsequent early growth of the seedlings. On the contrary, a detrimental action of the four-minute DBD subjection on seed germination and early growth of the sprouts was noted shortly after the treatment. However, this effect was no longer observed or reduced to 9.7% after the 96 h incubation period. Due to the application of optical emission spectrometry (OES), transmission electron microscopy (TEM), and confocal laser scanning microscopy (CLSM), we found that the generated reactive oxygen and nitrogen species (RONS), i.e., N2, N2+, NO, OH, NH, and O, probably led to the denaturation and aggregation of DNA, proteins, and ribosomes. Furthermore, the cellular membrane disrupted, leading to an outflow of the cytoplasm from the DBD-exposed cells. This study suggests the potential applicability of NTAPPs as eco-friendly and innovative plant protection methods.

Comparative genomics and pangenome-oriented studies reveal high homogeneity of the agronomically relevant enterobacterial plant pathogen Dickeya solani.

BACKGROUND: Dickeya solani is an important plant pathogenic bacterium causing severe losses in European potato production. This species draws a lot of attention due to its remarkable virulence, great devastating potential and easier spread in contrast to other Dickeya spp. In view of a high need for extensive studies on economically important soft rot Pectobacteriaceae, we performed a comparative genomics analysis on D. solani strains to search for genetic foundations that would explain the differences in the observed virulence levels within the D. solani population. RESULTS: High quality assemblies of 8 de novo sequenced D. solani genomes have been obtained. Whole-sequence comparison, ANIb, ANIm, Tetra and pangenome-oriented analyses performed on these genomes and the sequences of 14 additional strains revealed an exceptionally high level of homogeneity among the studied genetic material of D. solani strains. With the use of 22 genomes, the pangenome of D. solani, comprising 84.7% core, 7.2% accessory and 8.1% unique genes, has been almost completely determined, suggesting the presence of a nearly closed pangenome structure. Attribution of the genes included in the D. solani pangenome fractions to functional COG categories showed that higher percentages of accessory and unique pangenome parts in contrast to the core section are encountered in phage/mobile elements- and transcription- associated groups with the genome of RNS 05.1.2A strain having the most significant impact. Also, the first D. solani large-scale genome-wide phylogeny computed on concatenated core gene alignments is herein reported. CONCLUSIONS: The almost closed status of D. solani pangenome achieved in this work points to the fact that the unique gene pool of this species should no longer expand. Such a feature is characteristic of taxa whose representatives either occupy isolated ecological niches or lack efficient mechanisms for gene exchange and recombination, which seems rational concerning a strictly pathogenic species with clonal population structure. Finally, no obvious correlations between the geographical origin of D. solani strains and their phylogeny were found, which might reflect the specificity of the international seed potato market.

Rapid eradication of bacterial phytopathogens by atmospheric pressure glow discharge generated in contact with a flowing liquid cathode.

Diseases caused by phytopathogenic bacteria are responsible for significant economic losses, and these bacteria spread through diverse pathways including waterways and industrial wastes. It is therefore of high interest to develop potent methods for their eradication. Here, antibacterial properties of direct current atmospheric pressure glow discharge (dc-APGD) generated in contact with flowing bacterial suspensions were examined against five species of phytopathogens. Complete eradication of Clavibacter michiganensis subsp. sepedonicus, Dickeya solani, and Xanthomonas campestris pv. campestris from suspensions of OD600 ≈ 0.1 was observed, while there was at least 3.43 logarithmic reduction in population densities of Pectobacterium atrosepticum and Pectobacterium carotovorum subsp. carotovorum. Analysis of plasma-chemical parameters of the dc-APGD system revealed its high rotational temperatures of 2,300 ± 100 K and 4,200 ± 200 K, as measured from N2 and OH molecular bands, respectively, electron temperature of 6,050 ± 400 K, vibrational temperature of 4000 ± 300 K, and high electron number density of 1.1 × 1015 cm-1 . In addition, plasma treatment led to formation of numerous reactive species and states in the treated liquid, including reactive nitrogen and oxygen species such as NOx , NH, H2 O2 , O2 , O, and OH. Further examination revealed that bactericidal activity of dc-APGD was primarily due to presence of these reactive species as well as to UVA, UVB, and UVC irradiation generated by the dc-APGD source. Plasma treatment also resulted in an increase in temperature (from 24.2 to 40.2 °C) and pH (from 6.0 to 10.8) of bacterial suspensions, although these changes had minor effects on cell viability. All results suggest that the newly developed dc-APGD-based system can be successfully implemented as a simple, rapid, efficient, and cost-effective disinfection method for liquids originating from different industrial and agricultural settings.

Population Structure and Biodiversity of Pectobacterium parmentieri Isolated from Potato Fields in Temperate Climate.

Pectobacterium parmentieri (formerly Pectobacterium wasabiae) is a newly established species of pectinolytic plant-pathogenic bacteria responsible for the symptoms of soft rot and blackleg on potato. In this work, we describe biodiversity and the population structure of P. parmentieri strains isolated during two consecutive growing seasons from the seed potato fields in Poland. About 450 samples of diseased potato tubers, potato plants, or accompanying weeds were collected throughout the country and tested for the presence of P. parmentieri by molecular identification methods. We found that P. parmentieri strains commonly occur in almost all regions of Poland. Furthermore, these isolates constituted significant fraction of pectinolytic bacteria from seed potato fields because 16% (2013) and 13% (2014) of the analyzed plant samples were infected with P. parmentieri. Subsequently, a detailed characterization of the obtained strains was conducted basing on repetitive sequences profiling, recA-gene-based phylogeny, and phenotypic features. By applying repetitive extragenic palindromic sequence-based polymerase chain reaction (REP-PCR), we revealed the presence of five distinct genomic profiles among P. parmentieri strains, with profile I being the most abundant (approximately 44%). The performed recA gene-based phylogenetic analysis divided P. parmentieri isolates into two distinct clades, although the strains originating from different years did not group separately. Evaluation of the phenotypic traits playing crucial roles for the virulence of pectinolytic bacteria (namely, pectinase, cellulase and protease activities, and siderophore production, in addition to potato tissue maceration, swimming, and swarming motility) indicated some differences among the characterized strains. To the best of our knowledge, this is the first study that describes biodiversity and the population structure of P. parmentieri isolated in two growing seasons under temperate climate conditions and, hence, illustrates high heterogeneity within this species.

Biodiversity of Dickeya spp. Isolated from Potato Plants and Water Sources in Temperate Climate.

Bacteria from the genera Dickeya (formerly Erwinia chrysanthemi) and Pectobacterium (formerly E. carotovora) are the agents of blackleg and soft rot on many important crops. In 2005, Dickeya solani was isolated for the first time in Poland from a symptomatic potato plant. To establish the presence and diversity of Dickeya spp. in Poland, we surveyed potato fields and water sources, including surface waters near potato fields and water from potato-processing facilities and sewage plants. Only D. dianthicola and D. solani were isolated from symptomatic potato, and only D. zeae and D. chrysanthemi were isolated from water sources. The Dickeya spp. isolated from potato formed a relatively homogenous group, while those from water sources were more diverse. To our knowledge, this is the first comprehensive characterization of Dickeya spp. isolated during several years from regions with a temperate climate in Central Europe.

Phyloproteomic study by MALDI-TOF MS in view of intraspecies variation in a significant homogenous phytopathogen Dickeya solani.

Dickeya solani is an economically significant pectinolytic phytopathogen belonging to the Pectobacteriaceae family, which causes soft rot and blackleg diseases. Despite its notable impact on global potato production, there are no effective methods to control this pest. Here, we undertook a phyloproteomic study on 20 D. solani strains, of various origin and year of isolation, with matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS) supported by an in-depth characterization of the strains in terms of the virulence-associated phenotype. In spite of high homogeneity in this species, we herein revealed for the first time intraspecies variation in the MALDI-TOF MS protein profiles among the studied D. solani isolates. Finally, representative mass spectra for the four delineated clades are presented. A majority of the analysed D. solani strains showed high virulence potential, while two strains stood out in their growth dynamics, virulence factors production and ability to macerate plant tissue. Nonetheless, the metabolic profiles of D. solani strains turned out to be uniform, except for gelatinase activity. Given that all D. solani isolates distinctly grouped from the other Dickeya species in the MALDI-TOF MS analysis, there is strong evidence supporting the potential routine use of this method for fast and reliable to-species identification of D. solani isolates of environmental origin.

The chemical structure of the O-antigen and enterobacterial common antigen of Pectobacterium brasiliense NCPPB 4609TS.

Pectobacterium brasiliense is a widely distributed phytopathogenic bacterium that causes diseases such as soft rot and blackleg, leading to significant yield losses in potatoes as well as other vegetables and ornamental plants. Lipopolysaccharide (LPS) is an important virulence factor that plays an essential role in colonisation of plant tissues and overcoming the host defence mechanisms. The O-polysaccharide from the LPS of P. brasiliense strain NCPPB 4609TS (=CFBP 6617TS = LMG 21371TS = IFB5390) was structurally characterised using spectroscopic techniques and chemical methods. The analyses revealed that the polysaccharide repeating unit consists of Gal, GlcN and an unusual 3-amino-3,6-dideoxyglucose decorated with (R)-3-hydroxybutyric acid according to the structure shown below: In addition, another polysaccharide was isolated from bacterial cells, analysis of which led to the identification of an enterobacterial common antigen, containing N-acetyl-d-glucosamine, N-acetyl-d-mannosaminouronic acid, and 4-acetamido-4,6-dideoxy-d-galactose.

The chemical structure of the O-polysaccharide isolated from the lipopolysaccharide of Pectobacterium brasiliense IFB5527, a phytopathogenic bacterium of high economic importance.

Pectobacterium brasiliense is a widespread plant pathogenic bacterium classified to the Pectobacteriaceae family, which causes significant economic losses because of the developed soft rot and blackleg symptoms on potatoes and a wide spectrum of crops, vegetables, and ornamentals. One of the key virulence factors is a lipopolysaccharide due to its involvement in efficient colonisation of plant tissues and overcoming the host defence mechanisms. Thus, we structurally characterised the O-polysaccharide from the LPS of P. brasiliense strain IFB5527 (HAFL05) using chemical methods followed by GLC and GLC-MS as well as 1D and 2D NMR spectroscopy. The analyses revealed that the polysaccharide repeating unit consists of Fuc, Glc, GlcN and an unusual N-formylated 6-deoxy amino sugar, Qui3NFo, and has the structure shown below.

The structure of an abequose - containing O-polysaccharide isolated from Pectobacterium aquaticum IFB5637.

Soft rot and blackleg diseases, caused by pectinolytic bacteria from the numerous species of Dickeya and Pectobacterium, pose a serious threat to the world potato production. Besides, infections triggered by these pectinolytic bacteria lead to huge economic losses in the cultivation of other crops, vegetables, and ornamentals. Strains belonging to the genus Pectobacterium tend to be isolated from various environments such as rotten or asymptomatic plants, weeds, soil or water. The main virulence factors of these phytopathogenic bacteria involve plant cell wall degrading enzymes (PCWDEs) i.e. pectinases, cellulases and proteases. Among accessory virulence factors, there is often lipopolysaccharide (LPS) listed. This constituent of the external part of bacterial cell wall contains lipid A, inner and outer core in addition to O-polysaccharide (OPS). LPS plays an important role in plant-microbe interactions, in particular during the first step of pathogen recognition. In this study we present the chemical structure of OPS of the first Pectobacterium aquaticum strain (IFB5637) isolated from water in Poland. The OPS consists of two common hexoses, such as mannose and glucose, as well as an abequose (3,6-dideoxy-d-xylo-hexose), the first 3,6-dideoxyhexose identified among the Pectobacteriaceae family: According to our best knowledge this is the first determined structure of the OPS of P. aquaticum.

Application of pulse-modulated radio-frequency atmospheric pressure glow discharge for degradation of doxycycline from a flowing liquid solution.

Doxycycline (DOX), an antibiotic commonly used in medicine and veterinary, is frequently detected in natural waterways. Exposition of bacteria to DOX residuals poses a selective pressure leading to a common occurrence of DOX-resistance genetic determinants among microorganisms, including virulent human pathogens. In view of diminishment of the available therapeutic options, we developed a continuous-flow reaction-discharge system generating pulse-modulated radio-frequency atmospheric pressure glow discharge (pm-rf-APGD) intended for DOX removal from liquid solutions. A Design of Experiment and a Response Surface Methodology were implemented in the optimisation procedure. The removal efficiency of DOX equalling 79 ± 4.5% and the resultant degradation products were identified by High-Performance Liquid Chromatography-Diode Array Detection, Liquid Chromatography Quadruple Time of Flight Mass Spectrometry, Ultraperformance Liquid Chromatography-Tandem Mass Spectrometry, total organic carbon, total nitrogen, Attenuated Total Reflectance Furrier Transform-Infrared, and UV/Vis-based methods. The pm-rf-APGD-treated DOX solution due to the generated Reactive Oxygen and Nitrogen Species either lost its antimicrobial properties towards Escherichia coli ATCC25922 or significantly decreased biocidal activities by 37% and 29% in relation to Staphylococcus haemolyticus ATCC29970 and Staphylococcus aureus ATCC25904, respectively. Future implementation of this efficient and eco-friendly antibiotic-degradation technology into wastewater purification systems is predicted.

The First Polish Isolate of a Novel Species Pectobacterium aquaticum Originates from a Pomeranian Lake.

Pectinolytic bacteria from the genus Pectobacterium cause high economic losses in various crops, vegetables, and ornamentals including potato. Thus far, these strains have been isolated from distinct environments such as rotten or asymptomatic plants, soil, and waterways. The prevalence of soft rot Pectobacteriaceae in different depths of Pomeranian lakes was performed by a qualified scuba diver over 2 years of monitoring. It allowed for the isolation and broad characterization of a strain from the newly established species Pectobacterium aquaticum. Phylogenetic analysis on the sequences of dnaX and recA genes revealed the highest similarity of this strain to P. aquaticum CFBP 8637T. In addition to the determination of analytical profile index (API 20E), we discovered that this strain possesses a smooth form of a lipopolysaccharide with O-polysaccharide consisting of mannose, glucose, and abequose. Moreover, the characterized strain, described as P. aquaticum IFB5637, produced plant-cell-wall-degrading enzymes, such as pectinases, cellulases, proteases, and was capable of macerating potato and chicory tissues under laboratory conditions. In view of more frequent irrigation of seed potato fields resulting from the ongoing climate warming, it is important to monitor the occurrence of potential disease-causing agents in natural waterways.

The structure of the O-polysaccharide isolated from pectinolytic gram-negative bacterium Dickeya aquatica IFB0154 is different from the O-polysaccharides of other Dickeya species.

The species Dickeya aquatica was established in 2014 after the genomic characterization of the pectinolytic bacteria isolated from water. It was demonstrated that D. aquatica was able to cause symptoms of soft rot on the fruit of tomato and cucumber. According to earlier works, lipopolysaccharides are regarded as an important virulence factor of Pectobacteriaceae. An O-specific polysaccharide containing d-Fuc and l-Rha was obtained by mild acid hydrolysis of the lipopolysaccharide of D. aquatica IFB0154 (strain Dw044 isolated in Finland). By means of compositional analyses and NMR spectroscopy, the chemical repeating unit of the polymer was identified as a linear disaccharide of the structure shown below. The rhamnose residue was partially acetylated at O-2 or O-3. OAc (~40%) ↓2 →3)-α-d-Fucp-(1 â†’ 4)-α-l-Rhap-(1→ ↑3 OAc (~30%) The O-polysaccharides isolated from Dickeya dianthicola IFB0485 and Dickeya zeae IPO946 have a different structure, identical to that previously described for several strains of Dickeya solani and Dickeya dadantii 3937.

Antibacterial Activity of Fructose-Stabilized Silver Nanoparticles Produced by Direct Current Atmospheric Pressure Glow Discharge towards Quarantine Pests.

Development of efficient plant protection methods against bacterial phytopathogens subjected to compulsory control procedures under international legislation is of the highest concern having in mind expensiveness of enforced quarantine measures and threat of the infection spread in disease-free regions. In this study, fructose-stabilized silver nanoparticles (FRU-AgNPs) were produced using direct current atmospheric pressure glow discharge (dc-APGD) generated between the surface of a flowing liquid anode (FLA) solution and a pin-type tungsten cathode in a continuous flow reaction-discharge system. Resultant spherical and stable in time FRU-AgNPs exhibited average sizes of 14.9 ± 7.9 nm and 15.7 ± 2.0 nm, as assessed by transmission electron microscopy (TEM) and dynamic light scattering (DLS), respectively. Energy dispersive X-ray spectroscopy (EDX) analysis revealed that the obtained nanomaterial was composed of Ag while selected area electron diffraction (SAED) indicated that FRU-AgNPs had the face-centered cubic crystalline structure. The fabricated FRU-AgNPs show antibacterial properties against Erwinia amylovora, Clavibacter michiganensis, Ralstonia solanacearum, Xanthomonas campestris pv. campestris and Dickeya solani strains with minimal inhibitory concentrations (MICs) of 1.64 to 13.1 mg L-1 and minimal bactericidal concentrations (MBCs) from 3.29 to 26.3 mg L-1. Application of FRU-AgNPs might increase the repertoire of available control procedures against most devastating phytopathogens and as a result successfully limit their agricultural impact.

Application of Silver Nanostructures Synthesized by Cold Atmospheric Pressure Plasma for Inactivation of Bacterial Phytopathogens from the Genera Dickeya and Pectobacterium.

Pectinolytic bacteria are responsible for significant economic losses by causing diseases on numerous plants. New methods are required to control and limit their spread. One possibility is the application of silver nanoparticles (AgNPs) that exhibit well-established antibacterial properties. Here, we synthesized AgNPs, stabilized by pectins (PEC) or sodium dodecyl sulphate (SDS), using a direct current atmospheric pressure glow discharge (dc-APGD) generated in an open-to-air and continuous-flow reaction-discharge system. Characterization of the PEC-AgNPs and SDS-AgNPs with UV/Vis absorption spectroscopy, transmission electron microscopy, energy dispersive X-ray spectroscopy, and selected area electron diffraction revealed the production of spherical, well dispersed, and face cubic centered crystalline AgNPs, with average sizes of 9.33 ± 3.37 nm and 28.3 ± 11.7 nm, respectively. Attenuated total reflection-Fourier transformation infrared spectroscopy supported the functionalization of the nanostructures by PEC and SDS. Antibacterial activity of the AgNPs was tested against Dickeya spp. and Pectobacterium spp. strains. Both PEC-AgNPs and SDS-AgNPs displayed bactericidal activity against all of the tested isolates, with minimum inhibitory concentrations of 5.5 mg∙L-1 and 0.75-3 mg∙L-1, respectively. The collected results suggest that the dc-APGD reaction-discharge system can be applied for the production of defined AgNPs with strong antibacterial properties, which may be further applied in plant disease management.

Molecular methods as tools to control plant diseases caused by Dickeya and Pectobacterium spp: A minireview.

Dickeya spp. and Pectobacterium spp. are etiological agents of soft rot on crops, vegetables, and ornamentals. They also cause blackleg on potato. These pectinolytic phytopathogens are responsible for significant economic losses, mostly within the potato production sector. Importantly, there are no methods to eradicate these microorganisms once they have infected plant material. Solely preventive measures remain, including early detection and identification of the pathogens, monitoring of their spread in addition to planting certified seed material tested for latent infections. As proper identification of the causative agent allows for efficient limitation of disease spread, numerous detection and differentiation methods have been developed. Most commonly followed procedures involve: isolation of viable bacterial cells (alternatively post-enrichment) on semi-selective media, identification to species level by PCR (single, multiplex, Real time), serology or fatty acids profiling. Differentiation of the isolates is often accomplished by sequencing the housekeeping genes or molecular fingerprinting. In view of lowering total costs of next-generation sequencing (NGS), a huge amount of generated data reveals subtle differences between strains that have proven to be potentially useful for the establishment of specific novel detection pipelines. Successful implementation of molecular diagnostic methods is exemplified by 20-year studies on the populations of pectinolytic bacteria on potatoes in Poland. The presented work aims to gather the characteristics of Dickeya spp. and Pectobacterium spp. important for the identification process in addition to providing an overview of modern and newly developed specific, rapid, high-throughput and cost-effective screening methods for the detection and identification of these phytopathogens.

Growth of bacterial phytopathogens in animal manures.

Animal manures are routinely applied to agricultural lands to improve crop yield, but the possibility to spread bacterial phytopathogens through field fertilization has not been considered yet. We monitored 49 cattle, horse, swine, sheep or chicken manure samples collected in 14 Polish voivodeships for the most important plant pathogenic bacteria - Ralstonia solanacearum (Rsol), Xanthomonas campestris pv. campestris (Xcc), Pectobacterium carotovorum subsp. carotovorum (Pcc), Pectobacterium atrosepticum (Pba), Erwinia amylovora (Eam), Clavibacter michiganensis subsp. sepedonicus (Cms) and Dickeya sp. (Dsp). All of the tested animal fertilizers were free of these pathogens. Subsequently, the growth dynamics of Pba, Pcc, Rsol, and Xcc in cattle, horse, swine, sheep and chicken manures sterilized either by autoclaving or filtration was evaluated. The investigated phytopathogens did not exhibit any growth in the poultry manure. However, the manure filtrates originating from other animals were suitable for microbial growth, which resulted in the optical density change of 0.03-0.22 reached within 26 h (48 h Rsol, 120 h Xcc), depending on bacterial species and the manure source. Pcc and Pba multiplied most efficiently in the cattle manure filtrate. These bacteria grew faster than Rsol and Xcc in all the tested manure samples, both the filtrates and the autoclaved semi-solid ones. Though the growth dynamics of investigated strains in different animal fertilizers was unequal, all of the tested bacterial plant pathogens were proven to use cattle, horse, swine and sheep manures as the sources of nutrients. These findings may contribute to further research on the alternative routes of spread of bacterial phytopathogens, especially because of the fact that the control of pectionolytic bacteria is only based on preventive methods.

The uniform structure of O-polysaccharides isolated from Dickeya solani strains of different origin.

O-polysaccharides were isolated from lipopolysaccharides obtained from four different strains of plant pathogenic bacteria belonging to the species Dickeya solani: two of them were isolated in Poland (IFB0099 and IFB0158), the third in Germany (IFB0223) and the last one, D. solani Type Strain IPO2222, originated from the Netherlands. In addition, the O-polysaccharide of a closely related species D. dadantii strain 3937 was isolated. The purified polysaccharides of the five strains were analyzed using NMR spectroscopy and chemical methods. Sugar and methylation analyses, including absolute configuration assignment, together with NMR data revealed that all O-polysaccharides tested are homopolymers of 6-deoxy-d-altrose (d-6dAlt) the following structure: →2)-ß-d-6dAltp-(1→.