Control Of Bacterial Diseases Research Articles

Isolation, characterization, and whole genome sequencing analysis of Aeromonas veronii from Channa argus in China.

Aeromonas veronii has emerged as a significant pathogen that impacts both fish and mammals. Recently, an infectious disease characterized by multiple ulcers on the body surface with a high mortality rate occurred in Channa argus cultured in Jiangsu Province, China. A Gram-negative bacterial strain (Aer12) was isolated from the body surface of the diseased fish and identified as A. veronii by the physiological, biochemical, and 16S rRNA gene analysis. Intra-peritoneal injection of Aer12 into the healthy C. argus resulted in the development of multiple ulcers on the body surface, and the histopathological results showed that muscle tissue rupture was the most severe symptom. Aer12 showed both protease and lipase activities with no β-hemolytic activity. Furthermore, Aer12 contained seven virulence genes (aer, act, alt, fla, ascV, aexT, and ela) and one antibiotic resistance gene (qnrS) identified by the PCR assay. The results of whole genome sequencing revealed that Aer12 had a circular chromosome that measured 4,719,428bp. It comprised 4301 predicted protein-coding sequences (CDS) in addition to 31 rRNA, 124 tRNA, and 49 sRNA genes. Furthermore, a total of 676 virulence genes and 216 antibiotic resistance genes have been predicted. Aer12 was susceptible to 21 antibiotics, including ampicillin and erythromycin. The results of Chinese herbs susceptibility assay showed that Aer12 was highly susceptible to Sanguisorba officinalis, Galla chinensis, and Schisandra chinensis. The results of this study will serve as a reference for future research on the pathogenic mechanism of A. veronii and the prevention and control of bacterial diseases in C. argus farming.

Whole-Genome Sequence and Characterization of Ralstonia solanacearum MLY102 Isolated from Infected Tobacco Stalks

Background/Objectives: Bacterial wilt disease is a soil-borne disease caused by Ralstonia solanacearum that causes huge losses to crop economies worldwide. Methods: In this work, strain MLY102 was isolated and further identified as R. solanacearum from a diseased tobacco stalk. The genomic properties of MLY102 were explored by performing biochemical characterization, genome sequencing, compositional analysis, functional annotation and comparative genomic analysis. Results: MLY102 had a pinkish-red color in the center of the colony surrounded by a milky-white liquid with fluidity on TTC medium. The biochemical results revealed that MLY102 can utilize carbon sources, including D-glucose (dGLU), cane sugar (SAC) and D-trehalose dihydrate (dTRE). Genome sequencing through the DNBSEQ and PacBio platforms revealed a genome size of 5.72 Mb with a G+C content of 67.59%. The genome consists of a circular chromosome and a circular giant plasmid with 5283 protein-coding genes. A comparison of the genomes revealed that MLY102 is closely related to GMI1000 and CMR15 but has 498 special genes and 13 homologous genes in the species-specific gene family, indicating a high degree of genomic uniqueness. Conclusions: The unique characteristics and genomic data of MLY102 can provide important reference values for the prevention and control of bacterial wilt disease.

Pseudomonas rhodesiae HAI-0804 suppresses Pythium damping off and root rot in cucumber by its efficient root colonization promoted by amendment with glutamate

Plant diseases caused by soil-borne fungi and oomycetes significantly reduce yield and quality of many crops in the agricultural systems and are difficult to control. We herein examine Pseudomonas rhodesiae HAI-0804, a bacterial biological control agent that was originally developed for control of bacterial diseases on the surface of vegetables, and assessed its efficacy at controlling soil-borne diseases caused by oomycetes. Strain HAI-0804 did not exhibit detectable antibiotic activity toward Pythium ultimum, a causal agent of damping-off and root rot; however, it effectively protected against Pythium damping-off and root rot in cucumber. Exogenous glutamate enhanced the efficacy of biocontrol, the production of siderophore pyoverdine, root colonization in cucumber plants, and the ratio of biofilm formation to planktonic cells. The epiphytic fitness of strain HAI-0804 appears to contribute to plant protection efficacy against a broad spectrum of pathogens for both above-ground plant parts and the rhizosphere.

Effectiveness of Bacillus and Pseudomonas Strains in Biological Control of Common Bacterial Blight Disease in Common Bean (Phaseolus vulgaris L.)

Effectiveness of Bacillus and Pseudomonas Strains in Biological Control of Common Bacterial Blight Disease in Common Bean (Phaseolus vulgaris L.)

Paradendryphiella arenariae an endophytic fungus of Centella asiatica inhibits the bacterial pathogens of fish and shellfish.

Aquaculture has been considered a major food-producing sector in the world during the last few decades. The foremost constraint in the development of aquaculture is bacterial disease control and management. Since various fish pathogens are resistant to conservative treatments, it is essential to screen new and effective alternative antibacterial agents. Endophytic fungi are microorganisms that live in the plant's internal tissues without harming its host. Endophytic fungi have proven themselves as reliable sources of novel bioactive compounds that can be used as antibacterial agents. In the present study, fifteen morphologically different endophytic fungi were isolated from the fresh and healthy stem section of Centella asiatica. The active endophytic fungal crude extracts were tested for agar well diffusion assay, Minimum Inhibitory Concentration, Minimum Bactericidal Concentration assays, Time-kill kinetic analysis, Brine shrimp lethality assay. Agar plug diffusion and agar well diffusion assays revealed that endophytic fungus CAS1 exhibits maximum antagonistic activity against bacterial fish pathogens. The ethyl acetate crude extract of CAS1 exhibited the maximum zone of inhibitions against Aeromonas hydrophila (21 ± 0.11 mm), Aeromonas caviae (18 ± 0.1 mm), Edwardsiella tarda (23 ± 0.11 mm), Vibrio anguillarum (19 ± 0.05 mm) and Vibrio harveyi (20 ± 0.27 mm). The MIC and MBC values extract varied reliant on the trial pathogens ranging between 12.5-100 μg/mL and 25-100μg/mL correspondingly. The morphological and molecular characterization of potential isolate CAS1 was confirmed as Paradendryphiella arenariae by 18S rRNA ITS gene sequencing with 99.18% identity. This is the foremost findings to study the antagonistic effect of Paradendryphiella arenariae isolated from the stem of Centella asiatica against bacterial fish pathogens which can be used as natural effective antibacterial agents in aquaculture.

Role of hypothetical protein PA1-LRP in antibacterial activity of endolysin from a new Pantoea phage PA1.

Pantoea ananatis has emerged as a significant plant pathogen affecting various crops worldwide, causing substantial economic losses. Bacteriophages and their endolysins offer promising alternatives for controlling bacterial infections, addressing the growing concerns of antibiotic resistance. This study isolated and characterized the Pantoea phage PA1 and investigated the role of PA1-LRP in directly damaging bacteria and assisting endolysin PA1-Lys in cell lysis, comparing its effect to exogenous transmembrane domains following the identification and analysis of the PA1-Lys and the PA1-LRP based on whole genome analysis of phage PA1. Additionally, this study also explored how hydrophobic region of PA1-LRP (HPP) contributes to bacterial killing when combined with PA1-Lys and examined the stability and lytic spectrum of PA1-Lys under various conditions. Phage PA1 belonging to the Chaseviridae family exhibited a broad host range against P. ananatis strains, with a latent period of 40 minutes and a burst size of 17.17 phages per infected cell. PA1-Lys remained stable at pH 6-10 and temperatures of 20-50°C and showed lytic activity against various Gram-negative bacteria, while PA1-Lys alone could not directly lyse bacteria, its lytic activity was enhanced in the presence of EDTA. Surprisingly, PA1-LRP inhibited bacterial growth when expressed alone. After 24 h of incubation, the OD600 value of pET28a-LRP decreased by 0.164 compared to pET28a. Furthermore, the lytic effect of co-expressed PA1-LRP and PA1-Lys was significantly stronger than each separately. After 24 h of incubation, compared to pET28a-LRP, the OD600 value of pET28a-Lys-LRP decreased by 0.444, while the OD420 value increased by 3.121. Live/dead cell staining, and flow cytometry experiments showed that the fusion expression of PA1-LRP and PA1-Lys resulted in 41.29% cell death, with bacterial morphology changing from rod-shaped to filamentous. Notably, PA1-LRP provided stronger support for endolysin-mediated cell lysis than exogenous transmembrane domains. Additionally, our results demonstrated that the HPP fused with PA1-Lys, led to 40.60% cell death, with bacteria changing from rod-shaped to spherical and exhibiting vacuolation. Taken together, this study provides insights into the lysis mechanisms of Pantoea phages and identifies a novel lysis-related protein, PA1-LRP, which could have potential applications in phage therapy and bacterial disease control.

Effect of Acetic Acid on Biofilm Formation in Paracidovorax citrulli, Causal Agent of Bacterial Fruit Blotch.

The unique tissue structure of pathogenic bacteria biofilm plays an important role in its pathogenicity and bactericide resistance. Inhibition or destruction of biofilm formation of pathogenic bacteria is of great significance for the control of plant bacterial diseases. In this study, Paracidovorax citrulli was inoculated into KB medium containing acetic acid, and after shaking at 28°C and 55 r/min for 48 h, it was found that the content of extracellular polysaccharide, extracellular protein and extracellular DNA (eDNA) decreased with the increase of acetic acid concentration, which resulted in the decrease of biofilm formation, it is not even possible to form biofilms on plastic slides. When the final concentration of acetic acid in the culture medium was greater than or equal to 0.5 mg/mL, there was no biofilm on the plastic slides. Therefore, the use of acetic acid as an inhibitor of P. citrulli has a good potential for control of bacterial fruit blotch.

Phosphorus availability influences disease-suppressive soil microbiome through plant-microbe interactions.

Soil nutrient status and soil-borne diseases are pivotal factors impacting modern intensive agricultural production. The interplay among plants, soil microbiome, and nutrient regimes in agroecosystems is essential for developing effective disease management. However, the influence of nutrient availability on soil-borne disease suppression and associated plant-microbe interactions remains to be fully explored. This study aims to elucidate the mechanistic understanding of nutrient impacts on disease suppression, using phosphorous as a target nutrient. A 6-year field trial involving monocropping of tomatoes with varied fertilizer manipulations demonstrated that phosphorus availability is a key factor driving the control of bacterial wilt disease caused by Ralstonia solanacearum. Subsequent greenhouse experiments were then conducted to delve into the underlying mechanisms of this phenomenon by varying phosphorus availability for tomatoes challenged with the pathogen. Results showed that the alleviation of phosphorus stress promoted the disease-suppressive capacity of the rhizosphere microbiome, but not that of the bulk soil microbiome. This appears to be an extension of the plant trade-off between investment in disease defense mechanisms versus phosphorus acquisition. Adequate phosphorus levels were associated with elevated secretion of root metabolites such as L-tryptophan, methoxyindoleacetic acid, O-phosphorylethanolamine, or mangiferin, increasing the relative density of microbial biocontrol populations such as Chryseobacterium in the rhizosphere. On the other hand, phosphorus deficiency triggered an alternate defense strategy, via root metabolites like blumenol A or quercetin to form symbiosis with arbuscular mycorrhizal fungi, which facilitated phosphorus acquisition as well. Overall, our study shows how phosphorus availability can influence the disease suppression capability of the soil microbiome through plant-microbial interactions. These findings highlight the importance of optimizing nutrient regimes to enhance disease suppression, facilitating targeted crop management and boosting agricultural productivity. Video Abstract.

Smart nanoscale lamellated supramolecular assemblies overcome biofilm barriers and enhance foliar affinity for efficient control of bacterial diseases

Agricultural infections arising from morbigenous biofilms and biofilm-dispersed bacteria have become a huge obstacle, threatening global food supply and security. Recalcitrant dense biofilms assist the embedded pathogens to efficaciously evade the host immune responses and bactericidal attack, thereby causing inferior antibacterial efficacy and severe bacterial resistance. However, currently available bactericides don’t proclaim any competencies in inhibiting or eliminating intractable biofilms. Facing this daunting challenge, here, we have developed nanoscale lamellated supramolecular assemblies (PtA22@β-CD) integrated by a bioactive isopropanolamine-modified thiophenol (PtA22) and β-cyclodextrin (β-CD). These smart lamellar materials exhibit multipurpose orientations: (1) Strongly damaging mature biofilms of Xanthomonas citri (Xac) with a higher eradication rate of 91.9 % at 25 μg mL−1, after aged Xac for 24 h; (2) Killing biofilm-enclosed pathogenic bacteria that markedly reduces colony-forming units by 87.3 % at 25 μg mL−1; (3) Significantly weakening the biofilm-involved pathogenicity; (4) Enhancing foliar adhesion and deposition of PtA22@β-CD droplets. More attractively, in vivo pot experiments, PtA22@β-CD displayed excellent control efficiencies (protection 81.4 %, remediation 69.4 %, low-dose: 200 μg mL−1) against citrus bacterial canker, markedly overtopping the commercial thiodiazole-copper. Besides, PtA22@β-CD demonstrates broad-spectrum bioactivities against Xanthomonas oryzicola. This study is bright for enhancing agrochemical bioavailability and circumventing the large-scale use of hazardous traditional adjuvants.

Dynamic transcription analysis reveals the underlying key mechanism of L-arabinose-enhanced tomato resistance to bacterial wilt

Tomato bacterial wilt caused by Ralstonia solanacearum is a serious economic soil-borne disease worldwide. L-arabinose (L-Ara) increases tomato resistance to bacterial wilt, but the resistance mechanism remains unclear. In this study, we conducted an RNA sequencing (RNA-seq) analysis of tomato root and stem that exhibited differential expression in response to R. solanacearum infection at 2 dpi and 5 dpi under L-Ara application. As a result, 797 and 5605 differentially expressed genes (DEGs) were identified in response to R. solanacearum infection at 2 dpi and 5 dpi, respectively. In particular, 4504 DEGs with 2501 up-regulated and 2001 down-regulated were presented in the stem at 5 dpi, specifying that most defense responses were expressed at the wilting stage. In the function analysis (GO and KEGG), the DEGs were primarily enriched in response to stress, cell wall, glutathione and phenylpropanoid biosynthesis and plant hormone signaling transduction. Among the DEGs, potential candidate genes related to plant hormone biosynthesis and signaling, phenylpropanoid biosynthesis, and cell wall metabolism were perceived. Furthermore, the transcription factors had high expression in ERF, bHLH, C2H2, MYB, NAC, WRKY, HD-ZIP, bZIP, MYB-related, and GRAS families. This research could provide theoretical support and valuable resources for further study of the prevention and control of bacterial wilt disease under L-Ara treatment .

Microbial regulatory mechanisms of disease-resistant tobacco varieties in the prevention and control of bacterial wilt disease

Bacterial wilt disease poses a significant threat to the production and quality of tobacco. Disease-resistant varieties of tobacco are the primary means of preventing bacterial wilt, but the soil microbial mechanisms that alleviate this disease require further in-depth research. In our study, we analyzed the physicochemical and microbial properties of rhizosphere soil in four different disease-resistant varieties of tobacco. The treatments included: T1 (Chang Bo Huang; 100 % infection rate); T2 (Yun Yan 87; 80 % infection rate); T3 (K326; 50 % infection rate) and T4 (YAN YAN 97; 0 % infection rate). Our results showed that the T4 treatment improved the fresh biomass of tobacco by 35.42 % compared to the T1 treatment. In addition, a significant increase in soil pH and soil organic matter (SOM) from 4.98 and 1.24 % under T1 treatment to 5.86 and 1.38 % under T4 treatment, respectively. As the disease resistance of the tobacco variety improved was found, there was a noticeable upward trend in the number of operational taxonomic units (OTUs) in the rhizosphere soil, showing higher sensitivity compared to fungi. Additionally, rhizosphere soil from susceptible varieties exhibited higher levels of metabolites, resulting in the accumulation of acidic substances (6-aminopenicillanic acid, garcinia acid, and 4-decan-4-ylbenzenesulfonic acid). Moreover, these soil metabolites might have attracted certain pathogenic fungi (Monoblepharomycota), contributing to the spread of soil diseases. This study suggests that the rhizosphere soil of disease-resistant tobacco variety provides a better microecological environment which could inhibit accumulation of allelopathic substances and reduce the spread of bacterial wilt disease.

Near-Infrared Light-Mediated Antibacterial Photodynamic Therapy Based on Erythrosine-Functionalized Mesoporous Silica-Coated Upconversion Nanoplatform.

Infectious diseases caused by bacteria pose a serious threat to public health, and more worryingly, the unregulated application of antibiotics accelerates the emergence of bacterial resistance, presenting a major challenge to the effective treatment of infectious diseases caused by bacteria. Therefore, there is an urgent necessity to develop efficient and safe antimicrobial systems. Photodynamic therapy (PDT) is an attractive therapeutic approach that does not induce bacterial resistance. However, the clinical application of PDT has been limited by several factors, including the lower tissue penetration depth of photoactivation under visible light irradiation and the uncertain biosafety of photosensitizers (PS). This work presents an near infrared (NIR)-triggered core-shell upconversion nanoparticle-based PDT system composed of mesoporous silica-coated lanthanide-doped upconversion nanoparticles loaded with the photosensitizer erythrosine (UCSE). Upon NIR-triggering, erythrosine generates highly efficient reactive oxygen species that disrupt the cell membranes of Staphylococcus aureus and Escherichia coli, exhibiting a potent photodynamic antimicrobial effect. It is worth noting that the UCSE also exhibits excellent biosafety. In conclusion, we present an efficient NIR-triggered nanoantimicrobial system with excellent antimicrobial capacity and biosafety, which is a new therapeutic strategy for the control of bacterial infectious diseases.

Identification and biological control of bacterial leaf spot disease of cucurbits

Objective: The present study was conducted for isolation and detection of the phyto-pathogen responsible for bacterial leaf spot disease of cucurbits as well as evaluation of its biological control techniques. Methods: The pathogen of the disease was isolated from infected leaf of bitter gourd and cultured on Luria-Bertani (LB) growth medium. The morphological tests and biochemical tests revealed the isolated bacteria as gram negative. Furthermore, advanced molecular technique was applied to facilitate proper detection of the isolated bacteria. The PCR of the bacterial genomic DNA using specific primers generated clear band of approximately 1450 bp in gel electrophoresis. Results: In gram staining test, the bacterial strain was found to be rod shaped and pinkish in color and Gram-negative. All the biochemical test showed positive without mannitol salt agar. The nucleotide sequencing of 16S rDNA gene of the bacterial isolate showed 86.02% similarities with the original sequence of Xanthomonas cucurbitae. In antibiotic sensitivity assay, the antibiotic cefixime showed highest 28.0±0.7 mm diameter of inhibition zone against the tested bacteria. The highest antibacterial activity was 8.0±0.5 mm zone of inhibition by of Allium sativum. Conclusion: The present findings may be benevolent for the detection, characterization and development of biological control techniques to prevent the leaf spot disease of cucurbits crops in Bangladesh. It may help to find out the specific signaling pathway techniques for plant microbes relationship for disease formation in future.

Exogenously applied silver nanoparticles (AgNPs) differentially affect bacterial blight disease control in twenty-seven wheat cultivars

The bacterial blight of wheat is an important global disease causing a significant decline in crop yield. Nanotechnology offers a potential solution for managing plant diseases. Therefore, this research aimed to investigate the effectiveness of silver nanoparticles (AgNPs) in controlling bacterial blight in 27 locally grown wheat cultivars. The study examined the impact of AgNPs at three distinct time points: 1, 3, and 5 days after the onset of the disease. Biochemical assay revealed that one day after applying the disease stress, the Inia cultivar had the highest amount of soluble protein (55.60 μg.g−1FW) content in the treatment without AgNPs. The Azadi cultivar, without AgNPs treatment, had the lowest amount of soluble protein content (15.71 μg.g−1FW). The Tabasi cultivar had the highest activity of the superoxide dismutase (SOD) (61.62 mM.g−1FW) with the combination treatment of AgNPs. On the other hand, the Karchia cultivar had the lowest SOD activity (0.6 mM.g−1FW) in the treatment of disease without AgNPs. Furthermore, three days after the application of stress, the Mahdavi cultivar had the highest amount of soluble protein content (54.16 μg.g−1FW) in the treatment of disease without AgNPs. The Niknejad cultivar had the highest activity of the SOD (74.15 mM.g−1FW) with the combined treatment of the disease without AgNPs. The Kavir cultivar had the lowest SOD activity (1.95 mM.g−1FW) and the lowest peroxidase (POX) activity (0.241 mM g−1FW min−1) in the treatment of the disease with AgNPs. Five days after exposure to stress, the Mahooti cultivar had the highest SOD activity (88.12 mM.g−1FW) with the combined treatment of the disease with AgNPs, and the Karchia cultivar had the lowest SOD activity (2.39 mM.g−1FW) in the treatment of the disease with AgNPs. Further, the results indicated that exposure to AgNPs could improve the antioxidant properties of wheat seeds in blight-infected and disease-free conditions in some cultivars.

Trojan Horse virus delivering CRISPR-AsCas12f1 controls plant bacterial wilt caused by Ralstonia solanacearum.

Plant bacterial wilt caused by Ralstonia solanacearum results in huge losses. Accordingly, developing an effective control method for this disease is urgently required. Filamentous phages, which do not lyse host bacteria and exert minimal burden, offer a potential biocontrol solution. A filamentous phage RSCq that infects R. solanacearum was isolated in this study through genome mining. We constructed engineered filamentous phages based on RSCq by employing our proposed approach with wide applicability to non-model phages, enabling the exogenous genes delivery into bacterial cells. CRISPR-AsCas12f1 is a miniature class 2 type V-F CRISPR-Cas system. A CRISPR-AsCas12f1-based gene editing system that targets the key virulence regulator gene hrpB was developed, generating the engineered phage RSCqCRISPR-Cas. Similar to the Greek soldiers in the Trojan Horse, our findings demonstrated that the engineered phage-delivered CRISPR-Cas system could disarm the key "weapon," hrpB, of R. solanacearum, in medium and plants. Remarkably, pretreatment with RSCqCRISPR-Cas significantly controlled tobacco bacterial wilt, highlighting the potential of engineered filamentous phages as promising biocontrol agents against plant bacterial diseases.IMPORTANCEBacterial disease, one of the major plant diseases, causes huge food and economic losses. Phage therapy, an environmentally friendly control strategy, has been frequently reported in plant bacterial disease control. However, host specificity, sensitivity to ultraviolet light and certain conditions, and bacterial resistance to phage impede the widespread application of phage therapy in crop production. Filamentous phages, which do not lyse host bacteria and exert minimal burden, offer a potential solution to overcome the limitations of lytic phage biocontrol. This study developed a genetic engineering approach with wide applicability to non-model filamentous phages and proved the application possibility of engineered phage-based gene delivery in plant bacterial disease biocontrol for the first.

Influence of propiconazole and metconazole formulations on Bacillus subtilis vegetative cell growth and disease control of fruit crops.

Biological control agent (BCA) Bacillus subtilis formulated as Theia® is registered for control of fungal and bacterial diseases of fruit crops. Combinations of Theia® and strategic concentrations of two demethylation inhibitor (DMI) fungicides were investigated to explore potential synergisms. Bacteria were cultured in nutrient broth and combined with technical grades and two formulations of propiconazole (EC and WP) and metconazole (EC and WDG) at 0, 10, 50, 100, and 150 µg/ml active ingredient. After co-cultivation, optical density (OD600) and colony forming units (CFU/ml) were evaluated. In contrast to EC formulations, the WP or WDG formulations at 10 or 50 µg/ml of both DMIs did not affect vegetative cell growth. The mixture of Theia® and each formulated DMI at 50 µg/ml active ingredient resulted in a significant reduction of Monilinia fructicola lesion development on apple, Colletotrichum siamense lesion development on cherry, and Botrytis cinerea lesion development on cherry. The combination of Theia® with EC formulations showed weaker disease reduction due to antagonism. Only Theia® + non-EC formulated propiconazole and metconazole significantly reduced brown rot disease incidence of apple compared to the respective solo treatments and anthracnose disease incidence of cherry compared to the untreated control. Our results indicated that at least some DMI fungicides possess bactericidal effects depending on the formulation and concentration. The combination of Theia® with a lower than label rate concentration (50 µg/ml) of the DMI fungicides propiconazole and metconazole showed potential for synergistic effects especially when non-EC formulations were used.

Development of Tetramycin-Loaded Core–Shell Beads with Hot-/Wet-Responsive Release Properties for Control of Bacterial Wilt Disease

Plant bacterial wilt is caused by Ralstonia solanacearum, a soilborne pathogen that infects plant conduits, leading to wilt disease. It is extremely difficult to cure plants infected with Ralstonia solanacearum; however, bactericide-loaded beads with hot-/wet-responsive properties may be able to release a biocide in line with the increase in the hot-/wet-associated activity of Ralstonia solanacearum, effectively killing the pathogenic cells and providing high levels of plant protection. A biopesticide, Tetramycin, was embedded in corn kernel powder (CKP)-based cores. An oil-phase mixture was sprayed onto the core surface to form a hot-/wet-responsive intermediate shell (IMS). Subsequently, a layer of ethyl cellulose (EC) and hydroxypropyl methyl cellulose (HPMC) was coated onto the IMS to create a single wet-responsive outer shell (OTS). The ratios of the components in the cores, including the corn kernel powder (CKP), xanthan gum (XG), and Tetramycin, were optimized, as well as those of the IMS, including pentaerythrityl tetrastearate (PETS), pentaerythrityl tetraoleate (PETO), polyethylene glycol stearate (PEG400MS), and polyethylene glycol monooleate (PEG400MO), and those of the outer shell (OTS), including ethyl cellulose (EC) and hydroxypropyl methyl cellulose (HPMC). A texture performance analysis, differential scanning calorimetry (DSC) analysis, thermogravimetric analysis (TGA), temperature and humidity response performance tests, scanning electron microscope (SEM) observations, and a field effectiveness test were conducted to characterize the Tetramycin-loaded beads. The results indicated that the optimal formula for the bead cores comprised a mass ratio of CKP/Tetramycin solution/XG = 13.5:23:2. The preferred mass ratio for IMS was PETS/PETO/PEG400MO = 10:30:10, and the formula for the applicable OTS consisted of a mass ratio of EC/HPMC = 5:1. In soil with a temperature of 30–35 °C and humidity of 30%, the release period of the Tetramycin-loaded beads, with a cumulative release rate of over 95%, could last up to 35 days. Furthermore, the Tetramycin-loaded beads exhibited a gradual and multi-cyclic release process under alternating hot/wet and dry/cold environments. The relative preventive efficacy of 54.74% on tobacco was revealed at a field-testing scale. A significant reduction in the abundance of Ralstonia solanacearum was also observed under treatment with the Tetramycin-loaded beads. The early fungal community structure exhibited higher consistency compared to the control. However, in the later stage, the diversity differences between the soil layers were restored. In conclusion, Tetramycin-loaded beads that could effectively respond to temperature and humidity fluctuations were developed, resulting in enhanced disease prevention efficacy and offering broad prospects for the prevention and control of Ralstonia solanacearum in agricultural settings.

Nonphytotoxic and pH-responsive ZnO-ZIF‑8 loaded with honokiol as a “nanoweapon” effectively controls the soil-borne bacterial pathogen Ralstonia solanacearum

The development of intelligently released and environmentally safe nanocarriers not only aligns with the sustainable agricultural strategy but also offers a potential solution for controlling severe soil-borne bacterial diseases. Herein, the core-shell structured nanocarrier loaded with honokiol bactericide (honokiol@ZnO-ZIF-8) was synthesized via a one-pot method for the targeted control of Ralstonia solanacearum, the causative agent of tobacco bacterial wilt disease. Results indicated that honokiol@ZnO-ZIF-8 nanoparticles induced bacterial cell membrane and DNA damage through the production of excessive reactive oxygen species (ROS), thereby reducing bacterial cell viability and ultimately leading to bacterial death. Additionally, the dissociation mechanism of the nanocarriers was elucidated for the first time through thermodynamic computational simulation. The nanocarriers dissociate primarily due to H+ attacking the N atom on imidazole, causing the rupture of the Zn-N bond under acidic conditions and at room temperature. Furthermore, honokiol@ZnO-ZIF-8 exhibited potent inhibitory effects against other prominent Solanaceae pathogenic bacteria (Pseudomonas syringae pv. tabaci), demonstrating its broad-spectrum antibacterial activity. Biosafety assessment results indicated that honokiol@ZnO-ZIF-8 exhibited non-phytotoxicity towards tobacco and tomato plants, with its predominant accumulation in the roots and no translocation to aboveground tissues within a short period. This study provides potential application value for the intelligent release of green pesticides. Environment implicationThe indiscriminate use of agrochemicals poses a significant threat to environmental, ecological security, and sustainable development. Slow-release pesticides offer a green and durable strategy for crop disease control. In this study, we developed a non-phytotoxic and pH-responsive honokiol@ZnO-ZIF-8 nano-bactericide based on the pathogenesis of Ralstonia solanacearum. Thermodynamic simulation revealed the dissociation mechanism of ZIF-8, with different acidity controlling the dissociation rate. This provides a theoretical basis for on-demand pesticide release while reducing residue in the. Our findings provide strong evidence for effective soil-borne bacterial disease control and on-demand pesticide release.

Antimicrobial activities of essential oils from three species of citrus fruits against six infectious tropical bacteria: implications for the care and control of common bacterial tropical diseases in developing countries

The burden of bacterial infections and the failure of antimicrobial agents are increasing worldwide, especially in sub-Saharan Africa. This raises the need for novel therapeutic agents to combat bacterial infectious diseases. The sensitivity of several common pathogenic bacteria to essential oils from the peels of three species of citrus plants was investigated. Essential oils (EOs) were extracted from the fresh and dried peels of the citrus species using standard techniques. The antimicrobial activities of the EOs were determined using agar well diffusion and broth microdilution methods, and the activities of the EOs were compared to those of twelve conventional antibiotics. The results showed that the essential oils had high inhibitory effects. The minimum inhibitory concentrations (MICs) of the EOs ranged between 0.025 and 0.15 mg/ml. The activities of the EOs against the tested microorganisms were comparable to those of conventional antibiotics. Processing techniques did not affect the antibacterial activities of the EOs. Thus, the essential oils from the citrus species used against the investigated microorganisms were comparable to conventional antibiotics, and these findings showed that the oils could be widely applied in the health and pharmaceutical industries, where they could help in combating the menace of bacterial infections and therapeutic failure from drug resistance worldwide and especially in developing countries with limited resources available to combat these infections.

Antibacterial Activities and Underlying Mechanisms of the Compound SYAUP-491 against Xanthomonas oryzae pv. oryzae.

SYAUP-491 is a novel alkyl sulfonamide. In this study, in vivo and in vitro tests were performed along with a proteomic analysis to determine the effects and underlying mechanisms of the antibacterial activity of SYAUP-491 against the causative agent of bacterial leaf blight in rice. The antibacterial test results suggested that SYAUP-491 exhibited significant activities against Xanthomonas oryzae pv. oryzae (Xoo) in vitro and in vivo. The minimal EC50 values reached 6.96 μg/mL and the curative activity reached 74.1%. Detailed studies demonstrated that SYAUP-491 altered membrane permeability and caused morphological changes. Based on proteomics results, SYAUP-491 might inhibit bacterial protein synthesis. SYAUP-491 may disrupt and alter cell membrane permeability and could further act on ribosomes in the bacterial body. Given the above results, SYAUP-491 could serve as a new lead compound in the research of antibacterial control of plant pathogenic bacterial disease.