Control Of Bacterial Diseases Research Articles

Longitudinal Sampling of the Rainbow Trout (Oncorhynchus mykiss) Microbiome Reveals Effects of Dietary Cecropin A and Yersinia ruckeri Infection

The aquaculture industry faces growing pressure to reduce the use of antibiotics for control of bacterial diseases. In this study we tested the effectiveness of dietary cecropin A, an insect-derived antimicrobial peptide, at preventing mortality and reducing incidence of carrier status in rainbow trout (Oncorhynchus mykiss) challenged by immersion with Yersinia ruckeri. Additionally, we conducted longitudinal analyses of microbiome changes to elucidate effects of both cecropin A and bacterial infection. An in vitro experiment indicated that Y. ruckeri is susceptible to cecropin A. However, dietary cecropin A did not improve the survival of fish challenged with Y. ruckeri, nor did it decrease the persistence of Y. ruckeri in the intestine of fish that survived infection. Moreover, levels of intestinal Y. ruckeri as measured by qPCR suggested that cecropin A may have negatively impacted the ability of fish to resist colonization by this bacterial pathogen. Concomitantly with the survival experiments, the microbiomes of challenged and mock-challenged fish were sampled at days 0, 3, 8, and 30. The microbiomes were in general dominated by Mycoplasma sp. at days 0, 3 and 8, independent of diet, and whether fish had been challenged or mock-challenged. At day 30, the microbiomes of mock-challenged fish fed the +cecropin diet were characterized by lower internal (alpha) diversity (p<.01), greater relative abundance of Mycoplasma sp., and a decrease in gram-negative taxa, when compared to the microbiomes of fish fed the control diet. The opposite was observed in the microbiome of challenged fish. Lastly, correlation analysis of amplicon sequence variants (ASVs) revealed a negative correlation between the presence of Y. ruckeri and seven ASVs, including Mycoplasma sp., suggesting possible beneficial effects of these taxa. In addition, six ASVs were positively correlated to Y. ruckeri, including Flavobacterium succinicans – a known opportunistic fish pathogen. In conclusion, this study revealed that dietary cecropin A was bioactive and exerted significant effects on the microbiome but did not improve fish resistance to infection by Y. ruckeri. Based on our observations and other published results, it appears that high relative abundance of Mycoplasma sp. correlates with higher resistance to intestinal colonization by bacterial pathogens.

Genomic and Biological Profile of a Novel Bacteriophage, Vibrio phage Virtus, Which Improves Survival of Sparus aurata Larvae Challenged with Vibrio harveyi.

Due to the emergence of multidrug-resistant bacteria, commonly known as “superbugs”, phage therapy for the control of bacterial diseases rose in popularity. In this context, the use of phages for the management of many important bacterial diseases in the aquaculture environment is auspicious. Vibrio harveyi, a well-known and serious bacterial pathogen, is responsible for many disease outbreaks in aquaculture, resulting in huge economic and production losses. We isolated and fully characterized a novel bacteriophage, Vibrio phage Virtus, infecting V. harveyi strain VH2. Vibrio phage Virtus can infect a wide spectrum of Vibrio spp., including strains of V. harveyi, V. owensii, V. campbellii, V. parahaemolyticus, and V. mediterranei. It has a latent period of 40 min with an unusually high burst size of 3200 PFU/cell. Vibrio phage Virtus has a double-stranded DNA of 82,960 base pairs with 127 predicted open reading frames (ORFs). No virulence, antibiotic resistance, or integrase-encoding genes were detected. In vivo phage therapy trials in gilthead seabream, Sparus aurata, larvae demonstrated that Vibrio phage Virtus was able to significantly improve the survival of larvae for five days at a multiplicity of infection (MOI) of 10, which suggests that it can be an excellent candidate for phage therapy.

Qualitative Risk Assessment for Antimicrobial Resistance among Humans from Salmon Fillet Consumption Due to the High Use of Antibiotics against Bacterial Infections in Farmed Salmon.

Background: Worldwide, aquaculture is considered as a hotspot environment for antimicrobial resistance (AMR) due to the intense use of antibiotics in its productive systems. Chile is the second largest producer of farmed salmon worldwide, and tons of antibiotics are used to control bacterial diseases, such as Salmon Rickettsial Syndrome (SRS) and Bacterial Kidney Disease (BKD). However, studies determining the risk of consuming salmon fillets that have been treated with antibiotics during the salmon production are limited. Consulting leading experts in the field could provide a knowledge base to identify and address this question and research gaps. Methods: Multisectoral risk perception of AMR through salmon fillet consumption was evaluated by eliciting expert data obtained through discussions during a workshop and from questionnaires given to experts from academia (n = 15, 63%), the public sector (n = 5, 21%), and the salmon industry (n = 4, 17%). Results: The qualitative risk analysis suggested an overall ‘low’ probability of AMR acquisition by consumption of salmon fillet that had been treated during the production cycle. The risk perception varied slightly between production stages in freshwater and seawater. In consensus with all sectors, this overall ‘low’, but existing, risk was probably associated with bacterial infections and the use of antibiotics. Conclusions: As it is essential to reduce the use of antibiotics in the Chilean salmon industry, this intersectoral approach and consensual results could favor effective implementation of targeted initiatives for the control and prevention of major bacterial diseases.

Molecular-genetic structure of <i>Pseudomonas phage</i> BIM BV-45 D

Full nucleotide sequence of bacteriophage Pseudomonas phage BIM BV-45 D – active component of biopesticide Multiphage intended for control of crop bacterial diseases caused by Pseudomonas syringae was analyzed. It was found that phage genome is represented by linear double-stranded DNA sized 40383 b. p. (average GC contents equals 58 %), comprising 46 open reading frames, including 13 described in genomes of closely related phages. 4 control sequences typical for bacterial genes recognized by sigma factor (σ70) of RNA polymerase were detected, specific phage promoters were not localized. The identity was established of the majority of protein amino acid sequences of the Pseudomonas phage BIM BV-45 D with the proteins of the known Pseudomonas phage Andromeda (95‒100 %), at the same time, the sequences of the DNA endonuclease protein (gene 22) are similar (63 %) to the corresponding protein of Pseudomonas phage PollyC. The obtained data suggest that the mosaic structure of Pseudomonas phage BIM BV-45 D genome is due to recombinant rearrangements between the afore-mentioned phages.

Analysis on Prevention and Control of Bacterial Diseases in Cattle and Sheep

Analysis on Prevention and Control of Bacterial Diseases in Cattle and Sheep

Plant-associated microbiota as a source of antagonistic bacteria against the phytopathogen Erwinia amylovora.

Control of bacterial plant diseases is a major concern, as they affect economically important species and spread easily, such as the case of fire blight of rosaceous caused by Erwinia amylovora. In the search for alternatives to the use of agrochemicals and antibiotics, this work presents a screening of natural bacterial antagonists of this relevant and devastating phytopathogen. We recovered bacterial isolates from different plant tissues and geographical origins and then selected those with the strongest ability to reduce fire blight symptoms ex vivo and remarkable in vitro antagonistic activity against E. amylovora. None of them elicited a hypersensitivity reaction in tobacco leaves, most produced several hydrolytic enzymes and presented other biocontrol and/or plant growth-promoting activities, such as siderophore production and phosphate solubilization. These isolates, considered as biocontrol candidates, were identified by 16S rRNA sequencing as Pseudomonas rhizosphaerae, Curtobacterium flaccumfaciens, Enterobacter cancerogenus, Pseudomonas azotoformans, Rosenbergiella epipactidis and Serratia plymuthica. This is the first time that the last five bacterial species are reported to have biocontrol potential against E. amylovora.

Application and reflection of laboratory-based monitoring in early warning of infectious diseases

Despite the fact that our cognition towards infectious disease prevention, the advanced technology and the economic status of the whole society has made a great progress in the last decade, the outbreak of COVID-19 pneumonia has again enabled the public to acquire more about super-challenges of infectious diseases, epidemics and the relevant preventive measurements. In order to identify the epidemic signals in early stage or even before the onset of epidemic, the data research and utilization of a series of factors related to the occurrence and transmission of infectious diseases have played a significant role in research of prevention and control during the whole period of surveillance and early warning. Laboratory-based monitoring for the etiology has always been an important part of infectious disease warning system due to pathogens as the direct cause of such diseases. China has initially established a laboratory-based monitoring and early warning system for bacterial infectious diseases based on the Chinese Pathogen Identification Network with an aim to identify pathogens, outbreaks and sources. This network has played an essential role in early detection, tracking and precise prevention and control of bacterial infectious diseases, such as plague, cholera, and epidemic cerebrospinal meningitis. This issue focuses on the function of laboratory-based monitoring during the period of early warning, prevention, and control of bacterial infectious diseases, and conducted a wide range of researches based on the analysis of the epidemic and outbreak isolates, together with field epidemiological studies and normal monitoring systems. All of these could illustrate the effect of laboratory surveillance in the infectious disease risk assessment and epidemic investigation. At the same time, we have put forward our review and expectation of scenarios about laboratory-based monitoring and early warning technologies to provide innovative thoughts for promoting a leapfrog development of infectious disease monitoring and early warning system in China.

Active Metabolites From the Endophyte Paenibacillus polymyxa Y-1 of Dendrobium nobile for the Control of Rice Bacterial Diseases

Microbial bactericides have been a research hotspot in recent years. In order to find new microbial fungicides for preventing and treating rice bacterial diseases, Paenibacillus polymyxa Y-1 (P. polymyxa Y-1) was isolated from Dendrobium nobile in this study, and the optimal medium was selected by a single-factor experiment, and then eight metabolites were isolated from P. polymyxa Y-1 fermentation broth by bioactivity tracking separation. The bioassay results showed that 2,4-di-tert-butylphenol, N-acetyl-5-methoxytryptamine, and P-hydroxybenzoic acid have good antibacterial activity against Xanthomonas oryzae pv. Oryzicola (Xoo) and Xanthomonas oryzae pv. oryzae (Xoc), with 50% effective concentration values of 49.45 μg/ml, 64.22 μg/ml, and 16.32 μg/ml to Xoo, and 34.33 μg/ml, 71.17 μg/ml, and 15.58 μg/ml to Xoc, respectively, compared with zhongshengmycin (0.42 and 0.82 μg/ml, respectively) and bismerthiazol (85.64 and 92.49 μg/ml, respectively). In vivo experiments found that 2,4-di-tert-butylphenol (35.9 and 35.4%, respectively), N-acetyl-5-methoxytryptamine (42.9 and 36.7%, respectively), and P-hydroxybenzoic acid (40.6 and 36.8%, respectively) demonstrated excellent protective and curative activity against rice bacterial leaf blight, which were better than that of zhongshengmycin (38.4 and 34.4%, respectively). In addition, after 2,4-di-tert-butylphenol, N-acetyl-5-methoxytryptamine, and P-hydroxybenzoic acid acted on rice, SOD, POD, and CAD defense enzymes increased under the same condition. In conclusion, these results indicated that the activity and mechanism research of new microbial pesticides were helpful for the prevention and control of rice bacterial diseases.

Control of Bacterial Diseases of Banana Using CRISPR/Cas-Based Gene Editing.

Banana is an important staple food crop and a source of income for smallholder farmers in about 150 tropical and sub-tropical countries. Several bacterial diseases, such as banana Xanthomonas wilt (BXW), blood, and moko disease, cause substantial impacts on banana production. There is a vast yield gap in the production of bananas in regions where bacterial pathogens and several other pathogens and pests are present together in the same field. BXW disease caused by Xanthomonas campestris pv. musacearum is reported to be the most destructive banana disease in East Africa. The disease affects all the banana varieties grown in the region. Only the wild-type diploid banana, Musa balbisiana, is resistant to BXW disease. Developing disease-resistant varieties of bananas is one of the most effective strategies to manage diseases. Recent advances in CRISPR/Cas-based gene editing techniques can accelerate banana improvement. Some progress has been made to create resistance against bacterial pathogens using CRISPR/Cas9-mediated gene editing by knocking out the disease-causing susceptibility (S) genes or activating the expression of the plant defense genes. A synopsis of recent advancements and perspectives on the application of gene editing for the control of bacterial wilt diseases are presented in this article.

A novel quorum quencher, Rhodococcus pyridinivorans XN-36, is a powerful agent for the biocontrol of soft rot disease in various host plants

Quorum sensing (QS) is a microbial cell–cell communication mechanism that regulates the virulence factor production in numerous pathogens, which plays a key role in microbial infections. QS-mediated microbial infections can be blocked via quorum quenching (QQ), which disrupts QS either by degradation of QS signals or interference of signal generation or perception. The pathogenicity of various diseases, including Pectobacterium carotovorum, is regulated by N-acyl homoserine lactone (AHL), a widely conserved QS signaling molecule. P. carotovorum can induce soft rot in a variety of crops and cause great economic losses to agricultural production. In this study, a newly isolated bacterium of Rhodococcus pyridinivorans XN-36 was identified as a novel QQ strain that can effectively degrade AHL and reduce the disease severity of P. carotovorum in host plants. Strain XN-36 was capable of rapidly degrading AHL without a lag phase, and over 85% of AHL (0.5 mmol·L−1) was degraded within 96 h. The metabolic intermediates of AHL biodegradation were detected and identified by gas chromatography-mass spectrometry (GC–MS) as lactamide and propenamide. Based on the chemical structure of AHL and intermediate metabolites, a novel metabolic pathway of AHL in strain XN-36 was proposed, which suggests that AHL could be degraded first by cleavage of its amide bond, followed by hydrolysis of the lactonic ring and subsequent metabolism. In addition, strain XN-36 participated in efficient degradation of a wide range of AHL signaling molecules including N-(3-oxohexanoyl)-L-homoserine lactone (OHHL), N-hexanoyl-L-homoserine lactone (C6HSL), N-(3-oxooctanoyl)-L-homoserine lactone (3OC8HSL), and N-(3-oxododecanoyl)-L-homoserine lactone (3OC12HSL). Furthermore, the application of strain XN-36 as a biocontrol agent could substantially alleviate the soft rot disease caused by P. carotovorum to suppress tissue maceration in a variety of host plants, including Chinese cabbage (Brassica pekinensis(Lour.) Rupr.), carrot (Daucus carota L.) and potato (Solanum tuberosum L.). Similarly, the application of crude enzymes of strain XN-36 significantly attenuated the disease incidence and severity in host plants. Enzyme activity test indicated that strain XN-36 has acylase activity. These findings expand the application of QQ strains as biocontrol agents, while opening up new prospects for the control of QS-mediated bacterial diseases.

Fabrication of copper nanoparticle composite nanogel for high-efficiency management of Pseudomonas syringae pv. tabaci on tobacco.

Copper nanoparticles (CuNPs) can release copper ions (Cu2+ ) to control bacterial diseases on crops. However, the high concentration of the CuNPs applied in disease controlling can highly limit their application. In this work, by in situ reducing CuNPs in alginate nanogels and coated with cetyl trimethyl ammonium chloride (CTAC), a CuNP composite nanogel was fabricated as a new nanopesticide with low copper content. Data showed that the CTAC coating would affect the antibacterial activity and leaf surface adhesion of the nanogel, while CuNP content could also influence the membrane damage ability of the gel. The nanogel could depress the growth of bacteria by rupturing its membrane and show a minimum inhibitory concentration (MIC) as low as 500 μg mL-1 , which only contain 58 μg mL-1 CuNP, and achieve a 64% of therapeutic efficiency (with 1000 μg mL-1 nanogel) in in vivo experiments, higher than that of commercial bactericide thiodiazole copper. Furthermore, the application of the nanogel can also perform a growth-promoting effect on the plant, which may be due to the supplement of copper element provided by CuNP. The CuNP composite nanogel fabricated in this work performed high leaf disease controllability and safety compared to the commercial bactericide thiodiazole copper. We hope this nanogel can provide a potential high-efficiency nano-bactericide that can be used in the leaf bacterial disease control.

Expression of a sphingomyelinase‐coding gene from Trichoderma harzianum conferred bacterial tolerance in tobacco

AbstractDiseases caused by bacteria are an important and widespread constraint, occurring in almost all crops, including vegetables, pulses, cereals, ornamentals, fruit and forages. Although several strategies have been developed to obtain disease resistance in plants using genetic engineering, few studies have effectively demonstrated the control of bacterial diseases. It has previously been reported that a gene encoding a sphingomyelinase (ThSMase), identified in Trichoderma harzianum, is up‐regulated during biocontrol against phytopathogens, and this may have biotechnological applications. SMases are involved in multiple cellular functions, including the immune response against pathogens. We hypothesized that the expression of this gene from fungi in transgenic tobacco could generate resistance to plant pathogens. ThSMase was cloned under control of the double CaMV 35S promoter plus a leader sequence from alfalfa mosaic virus (AMV), and stably introduced and expressed in tobacco. Reverse transcription‐quantitative PCR analysis revealed that the ThSMase gene was expressed at similar levels in all transgenic lines tested. Our results showed no statistically significant difference in susceptibility after challenging transgenic and nontransgenic lines with the fungus Sclerotinia sclerotiorum. However, transgenic tobacco plants revealed a significant resistance to the bacterium Pseudomonas syringae pv. tabaci, and a tolerance to Xylella fastidiosa. Our results demonstrated the strong potential of ThSMase in biotechnological processes such as molecular breeding of the plants.

Degradable Bactericide Constructed Using a Charge-Reversal Surfactant against Plant Pathogenic Bacteria.

Plant bacterial diseases are serious problems in agriculture, posing threats to global food security and the agricultural economy. Here, a degradable agricultural bactericide AMC-10 constructed using a charge-reversal surfactant, from being positively charged to negatively charged, was designed and synthesized. AMC-10 possessed high bactericidal activity toward plant pathogenic bacteria, consequently being able to inhibit the corresponding plant bacterial diseases. After degradation by water, the hydrolyzed products were nontoxic to bacteria and human cells. Such a degradable bactericide provides new ideas for the design of environmentally friendly agricultural bactericides. It is anticipated that degradable bactericides such as AMC-10 can be applied in the prevention and control of plant bacterial diseases, being less likely to produce toxicity or drug resistance.

PH-Responsive On-Demand Alkaloids Release from Core-Shell ZnO@ZIF-8 Nanosphere for Synergistic Control of Bacterial Wilt Disease.

Developing an effective and safe technology to control severe bacterial diseases in agriculture has attracted significant attention. Here, ZnO nanosphere and ZIF-8 are employed as core and shell, respectively, and then a pH-responsive core-shell nanocarrier (ZnO-Z) was prepared by in situ crystal growth strategy. The bactericide berberine (Ber) was further loaded to form Ber-loaded ZnO-Z (Ber@ZnO-Z) for control of tomato bacterial wilt disease. Results demonstrated that Ber@ZnO-Z could release Ber rapidly in an acidic environment, which corresponded to the pH of the soil where the tomato bacterial wilt disease often outbreak. In vitro experiments showed that the antibacterial activity of Ber@ZnO-Z was about 4.5 times and 1.8 times higher than that of Ber and ZnO-Z, respectively. It was because Ber@ZnO-Z could induce ROS generation, resulting in DNA damage, cytoplasm leakage, and membrane permeability changes so the released Ber without penetrability more easily penetrated the bacteria to achieve an efficient synergistic bactericidal effect with ZnO-Z carriers after combining with DNA. Pot experiments also showed that Ber@ZnO-Z significantly reduced disease severity with a wilt index of 45.8% on day 14 after inoculation, compared to 94.4% for the commercial berberine aqueous solution. More importantly, ZnO-Z carriers did not accumulate in aboveground parts of plants and did not affect plant growth in a short period. This work provides guidance for the effective control of soil-borne bacterial diseases and the development of sustainable agriculture.

Genomic and Functional Dissections of Dickeya zeae Shed Light on the Role of Type III Secretion System and Cell Wall-Degrading Enzymes to Host Range and Virulence.

ABSTRACTDickeya zeae is a worldwide destructive pathogen that causes soft rot diseases on various hosts such as rice, maize, banana, and potato. The strain JZL7 we recently isolated from clivia represents the first monocot-specific D. zeae and also has reduced pathogenicity compared to that of other D. zeae strains (e.g., EC1 and MS2). To elucidate the molecular mechanisms underlying its more restricted host range and weakened pathogenicity, we sequenced the complete genome of JZL7 and performed comparative genomic and functional analyses of JZL7 and other D. zeae strains. We found that, while having the largest genome among D. zeae strains, JZL7 lost almost the entire type III secretion system (T3SS), which is a key component of the virulence suite of many bacterial pathogens. Importantly, the deletion of T3SS in MS2 substantially diminished the expression of most type III secreted effectors (T3SEs) and MS2’s pathogenicity on both dicots and monocots. Moreover, although JZL7 and MS2 share almost the same repertoire of cell wall-degrading enzymes (CWDEs), we found broad reduction in the production of CWDEs and expression levels of CWDE genes in JZL7. The lower expression of CWDEs, pectin lyases in particular, would probably make it difficult for JZL7 to break down the cell wall of dicots, which is rich in pectin. Together, our results suggest that the loss of T3SS and reduced CWDE activity together might have contributed to the host specificity and virulence of JZL7. Our findings also shed light on the pathogenic mechanism of Dickeya and other soft rot Pectobacteriaceae species in general.IMPORTANCE Dickeya zeae is an important, aggressive bacterial phytopathogen that can cause severe diseases in many crops and ornamental plants, thus leading to substantial economic losses. Strains from different sources showed significant diversity in their natural hosts, suggesting complicated evolution history and pathogenic mechanisms. However, molecular mechanisms that cause the differences in the host range of D. zeae strains remain poorly understood. This study carried out genomic and functional dissections of JZL7, a D. zeae strain with restricted host range, and revealed type III secretion system (T3SS) and cell wall-degrading enzymes (CWDEs) as two major factors contributing to the host range and virulence of D. zeae, which will provide a valuable reference for the exploration of pathogenic mechanisms in other bacteria and present new insights for the control of bacterial soft rot diseases on crops.

Potassium Phosphite Enhances the Antagonistic Capability of Bacillus amyloliquefaciens to Manage Tomato Bacterial Wilt.

Bacterial wilt caused by Ralstonia solanacearum is a distributed and worldwide soilborne disease. The application of biocontrol microbes or agricultural chemicals has been widely used to manage tomato bacterial wilt. However, whether and how agricultural chemicals affect the antagonistic ability of biocontrol microbes is still unknown. Here, we combined potassium phosphite (K-Phite), an environmentally friendly agricultural chemical, and the biocontrol agent Bacillus amyloliquefaciens QPF8 (strain F8) to manage tomato bacterial wilt disease. First, K-Phite at a concentration of 0.05% (wt/vol) could significantly inhibit the growth of R. solanacearum. Second, 0.05% K-Phite enhanced the antagonistic capability of B. amyloliquefaciens F8. Third, the greenhouse soil experiments showed that the control efficiency for tomato bacterial wilt in the combined treatment was significantly higher than that of the application of B. amyloliquefaciens F8 or K-Phite alone. Overall, our results highlighted a novel strategy for the control of tomato bacterial wilt disease via application and revealed a new integrated pattern depending on the enhancement of the antagonistic capability of biocontrol microbes by K-Phite.

Nanoparticles in inhibiting Pantoea ananatis and to control maize white spot

ABSTRACT: Maize white spot (MWS) caused by Pantoea ananatis is one main maize leaf diseases, and nanoparticles (NPs) are an innovative approach for bacterial disease control. This research evaluated the toxicity of pure NPs and doped NPs with different elements in inhibiting bacterial growth and to control MWS. Pure NPs and ZnO NPs doped with silver (Ag), gold (Au), copper (Cu), iron (Fe), manganese (Mn), and nickel (Ni) at different concentrations were used to determine the toxicity for P. ananatis in vitro, evaluating the bacterial growth inhibition zone. To assess the control of MWS, in the preventive application, maize plants were sprayed with NPs of ZnO:0.1Cu, ZnO:0.05Fe, ZnO:0.2Mn and ZnO:0.7Ni at 10, 5 or 2.5 mg mL-1, and after 3 days, the plants were inoculated with bacterial suspension. To assess the curative application, plants were inoculated with the bacteria, and 3 days later sprayed with the NPs. The disease severity was assessed and the area under the disease-progress curve (AUDPC) was calculated. The doped ZnO NPs with different elements, and at different concentrations inhibited bacterial growth in vitro. NPs of ZnO:0.1Cu and ZnO:0.2Mn at 5 or 2.5 mg mL-1, in both applications reduced the severity of MWS, showing potential for use in the disease management.

Effect of the Nanoparticle Exposures on the Tomato Bacterial Wilt Disease Control by Modulating the Rhizosphere Bacterial Community.

Ralstonia Solanacearum is one of the most infectious soil-borne bacterial plant pathogens, causing tomato bacterial wilt (TBW). Nanotechnology is an emerging area of research, particularly the application of nanoparticles (NPs) as nanopesticides to manage plant disease is gaining attention nowadays. However, the interaction between NPs and rhizosphere bacterial communities remains largely elusive. This study indicated that metal NPs (CuO, ZnO, and FeO) reduced the incidence of bacterial wilt to varying degrees and affected the composition and structure of the rhizosphere bacterial community. The results revealed that the application of metal oxide NPs can improve the morphological and physiological parameters of TBW infected tomato plants. Among all, CuONPs amendments significantly increase the Chao1 and Shannon index. In the early stage (the second week), it significantly reduces the relative abundance of pathogens. However, the relative abundance of beneficial Streptomyces bacteria increased significantly, negatively correlated with the relative abundance of pathogenic bacteria. In addition, the nano-treatment group will enrich some potential beneficial bacteria such as species from Sphingomonadaceae, Rhizobiaceae, etc. In general, our research provides evidence and strategies for preventing and controlling soil-borne disease tomato bacterial wilt with metal oxide NPs.

Characterization, Pathogenicity, Phylogeny, and Comparative Genomic Analysis of Pseudomonas tolaasii Strains Isolated from Various Mushrooms in China.

Since 2016, devastating bacterial blotch affecting the fruiting bodies of Agaricus bisporus, Cordyceps militaris, Flammulina filiformis, and Pleurotus ostreatus in China has caused severe economic losses. We isolated 102 bacterial strains and characterized them polyphasically. We identified the causal agent as Pseudomonas tolaasii and confirmed the pathogenicity of the strains. A host range test further confirmed the pathogen's ability to infect multiple hosts. This is the first report in China of bacterial blotch in C. militaris caused by P. tolaasii. Whole-genome sequences were generated for three strains: Pt11 (6.48 Mb), Pt51 (6.63 Mb), and Pt53 (6.80 Mb), and pangenome analysis was performed with 13 other publicly accessible P. tolaasii genomes to determine their genetic diversity, virulence, antibiotic resistance, and mobile genetic elements. The pangenome of P. tolaasii is open, and many more gene families are likely to emerge with further genome sequencing. Multilocus sequence analysis using the sequences of four common housekeeping genes (glns, gyrB, rpoB, and rpoD) showed high genetic variability among the P. tolaasii strains, with 115 strains clustered into a monophyletic group. The P. tolaasii strains possess various genes for secretion systems, virulence factors, carbohydrate-active enzymes, toxins, secondary metabolites, and antimicrobial resistance genes that are associated with pathogenesis and adapted to different environments. The myriad of insertion sequences, integrons, prophages, and genome islands encoded in the strains may contribute to genome plasticity, virulence, and antibiotic resistance. These findings advance understanding of the determinants of virulence, which can be targeted for the effective control of bacterial blotch disease.

Evaluating Phage Tail Fiber Receptor-Binding Proteins Using a Luminescent Flow-Through 96-Well Plate Assay.

Phages have demonstrated significant potential as therapeutics in bacterial disease control and as diagnostics due to their targeted bacterial host range. Host range has typically been defined by plaque assays; an important technique for therapeutic development that relies on the ability of a phage to form a plaque upon a lawn of monoculture bacteria. Plaque assays cannot be used to evaluate a phage’s ability to recognize and adsorb to a bacterial strain of interest if the infection process is thwarted post-adsorption or is temporally delayed, and it cannot highlight which phages have the strongest adsorption characteristics. Other techniques, such as classic adsorption assays, are required to define a phage’s “adsorptive host range.” The issue shared amongst all adsorption assays, however, is that they rely on the use of a complete bacteriophage and thus inherently describe when all adsorption-specific machinery is working together to facilitate bacterial surface adsorption. These techniques cannot be used to examine individual interactions between a singular set of a phage’s adsorptive machinery (like long tail fibers, short tail fibers, tail spikes, etc.) and that protein’s targeted bacterial surface receptor. To address this gap in knowledge we have developed a high-throughput, filtration-based, bacterial binding assay that can evaluate the adsorptive capability of an individual set of a phage’s adsorption machinery. In this manuscript, we used a fusion protein comprised of an N-terminal bioluminescent tag translationally fused to T4’s long tail fiber binding tip (gp37) to evaluate and quantify gp37’s relative adsorptive strength against the Escherichia coli reference collection (ECOR) panel of 72 Escherichia coli isolates. Gp37 could adsorb to 61 of the 72 ECOR strains (85%) but coliphage T4 only formed plaques on 8 of the 72 strains (11%). Overlaying these two datasets, we were able to identify ECOR strains incompatible with T4 due to failed adsorption, and strains T4 can adsorb to but is thwarted in replication at a step post-adsorption. While this manuscript only demonstrates our assay’s ability to characterize adsorptive capabilities of phage tail fibers, our assay could feasibly be modified to evaluate other adsorption-specific phage proteins.