Investigation of the antibacterial mechanism of the novel bactericide dioctyldiethylenetriamine (Xinjunan)

A combination of genome mining with OSMAC strategy facilitates the discovery of bioactive metabolites produced from termite-associated Streptomyces tanashiensis BYF-112

BACKGROUND

Previously, eight new alkaloids were obtained from the fermentation extract of termite-associated Streptomyces tanashiensis BYF-112. However, genome analysis indicated the presence of many undiscovered secondary metabolites in S. tanashiensis BYF-112.

RESULTS

Herein, 12 new alkaloids, tianwuine A-E (1-5), cephalandole C (6), venezuelines I-L (7-10), N-(4-methylphenyl-2-hydroxy) formamide (11) and N-(5-formyl-2-hydroxyphenyl) formamide (12), as well as three known metabolites (13-15) were discovered from BYF-112 based on a combination of genome mining and the one strain many compounds (OSMAC) strategy. Plausible biosynthetic pathways of 1-13 were proposed using bioinformatic analysis of the full genome of BYF-112. Partial metabolites were evaluated in vitro for their antibacterial, phytotoxic, and anti-inflammatory activities. Pyrroloformamide A (14) showed strong antibacterial activities against Staphylococcus aureus, methicillin-resistant Staphylococcus aureus, Pseudomonas syringae pv. actinidae, Xanthomonas oryzae pv. oryzae and Xanthomonas oryzae pv. oryzicola at a concentration of 50 μg per 6 mm disk. Simultaneously, pyrroloformamide A (14) also had a strong inhibitory effect on the radicle growth of Echinochloa crusgalli with an inhibition rate of 98.01% at a concentration of 100 μg/mL, equivalent to the positive 2,4-dichlorophenoxyacetic acid. Subsequently, the possible herbicidal mechanism of 14 was explored using molecular docking simulation. In addition, venezueline G (13) displayed a strong inhibitory effect of NO production, with an half-maximal inhibitory concentration (IC50) value of 2.3 μm, which was comparable with that of BAY 11-7082 with an IC50 value of 2.1 μm.

CONCLUSION

These findings revealed a perspective for the development of novel bioactive drugs in the food, agricultural, and biomedical fields utilizing the metabolites of BYF-112. © 2025 Society of Chemical Industry.

Design, Synthesis, Antibacterial Activity, and Antivirulence Factor of Novel 1,2,4-Thiadiazole Derivatives Containing an Amide Moiety

To develop antibacterial agents with novel mechanisms of action, a series of novel 1,2,4-thiadiazole derivatives containing amide structures were designed and synthesized. The antibacterial activities of derivatives against Xanthomonas oryzae pv. oryzicola (Xoc), Xanthomonas oryzae pv. oryzae (Xoo), and Pseudomonas syringae pv. actinidiae (Psa) were evaluated, and all derivatives were exhibited excellent antibacterial activities. Among them, compound Z4 demonstrated significant antibacterial activities against Xoo, Xoc, and Psa, with EC50 values of 0.32, 0.43, and 11.06 mg/L, respectively. Compound Z4 exhibited a protective activity of 49.42% and a curative activity of 44.93% against rice bacterial leaf blight. In addition, compound Z4 could inhibit pathogenic bacteria by inhibiting a variety of virulence factors (exopolysaccharides, biofilms, motility, and extracellular enzymes). Compound Z4 stimulated the biochemical process of rice self-defense signaling by affecting cell transcription and translation and induced rice self-defense genes and controlled hypersensitivity reactions to resist pathogen infection.

Discovery of Novel Antibacterial Agents against Plant Pathogens: Design, Synthesis, Antibacterial Activity, and Mechanism of Action of 1,2,4-Thiadiazole Derivatives Containing a Sulfone Moiety

1,2,4-Thiadiazole derivatives containing a sulfone moiety were designed and synthesized via scaffold hopping to facilitate the discovery of novel antibacterial agents. Most of the compounds exhibited excellent activity against three plant pathogenic bacteria. The half-maximal effective concentrations (EC50) of compound B7 for Xanthomonas oryzae pv oryzae (Xoo) and X. oryzae pv oryzicola (Xoc) concentrations were 0.4 and 1.0 mg/L, respectively. In addition, the EC50 values of compounds B1 and B24 for Xoo, Xoc, and Pseudomonas syringae pv actinidiae (Psa) were less than 5 mg/L and significantly better than those of the positive control agents thiodiazole copper (121.8, 119.5, and 142.0 mg/L, respectively) and bismerthiazol (73.3, 65.6, and 128.8 mg/L, respectively). Compound B7 exhibited protective and curative activities of 48.1 and 46.7%, respectively, against bacterial leaf blight, which were higher than those of bismerthiazol (35.5 and 36.9%, respectively) and thiodiazole copper (39.3 and 39.5%, respectively). Additionally, compound B7 exerted an effect on the virulence factors of Xoo (production of exopolysaccharides and extracellular enzymes, biofilm formation, and motility), membrane permeability, cell surface morphology, and intracellular content of reactive oxygen species. Transcriptome analysis showed that compound B7 improved the resistance of rice plants to external stress by influencing the metabolic process, biological regulation, catalytic activity of enzymes, and plant-pathogen interaction. Compound B7 can therefore be considered as a potential candidate antibacterial agent and warrants an in-depth investigation in the future.

Antibacterial and antifungal pyrazoles based on different construction strategies

The growing prevalence of microbial infections, and antimicrobial resistance (AMR) stemming from the overuse and misuse of antibiotics, call for novel therapeutic agents, particularly ones targeting resistant microbial strains. Scientists are striving to develop innovative agents to tackle the rising microbial infections and abate the risk of AMR. Pyrazole, a five-membered heterocyclic compound belonging to the azole family, is a versatile scaffold and serves as a core structure in many drugs with antimicrobial and other therapeutic effects. In this review, we have updated pyrazole-based antibacterial and antifungal agents mainly developed between 2016 and 2024, by combining with diverse pharmacophores such as coumarin, thiazole, oxadiazole, isoxazole, indole, etc. Meanwhile, the various strategies (molecular hybridization, bioisosterism, scaffold hopping, multicomponent reactions, and catalyst-free synthesis) for integrating different functional groups with the pyrazole ring are discussed. Additionally, structure-activity relationships of these pyrazole derivatives, i.e., how structural modifications impact their selectivity and therapeutic potential against bacterial and fungal strains, are highlighted. This review provides insights into designing next-generation antimicrobials to combat AMR, and offers valuable perspectives to the scientists working on heterocyclic compounds with diverse bioactivities.

The exploration of pasteurization processes and mechanisms of inactivation of Bacillus cereus ATCC 14579 using radio frequency energy

Radio frequency (RF) heating has been utilized to investigate sterilization techniques, but the mechanism of sterilization via RF heating, particularly on Bacillus cereus (B. cereus), has not been thoroughly examined. In this paper, sterilization processes and potential bactericidal mechanisms of B. cereus using RF were investigated. The best heating and sterilization efficiency was achieved at (Electrode gap 130 mm, conductivity of bacterial suspension 0.1 S/m, volume of bacterial suspension 40 mL). Heating a suspension of B. cereus to 90 °C in 80 s using RF reduced the number of viable bacteria by 4.87 logarithms. At the cellular level, there was a significant leakage of nucleic acids and proteins from the bacterial cells. Additionally, the integrity of the cell membrane was severely damaged, with a decrease in ATP concentration of 2.08 mM, Na, K-ATPase activity to 10.7 (U/109 cells), and Ca, Mg-ATPase activity to 11.6 (U/109 cells). At the molecular level, transcriptomics analysis showed that RF heating of B. cereus to 65 °C produced 650 more differentially expressed genes (DEGs) compared with RF heating to 45 °C. The GO annotation analysis indicated that the majority of differentially expressed genes (DEGs) were predominantly associated with cellular components. KEGG metabolic analysis showed enrichment in microbial metabolism in diverse environments, etc. This study investigated the potential bactericidal mechanism of B. cereus using RF, and provided some theoretical basis for the research of the sterilization of B. cereus.

Effect of caffeic acid grafted chitosan loaded quercetin lyophilized powder formulation on avian colibacillosis and tissue distribution

Quercetin (QR), recognized as a natural antibacterial ingredient, has found widespread application in the poultry industry. This study investigated the bacteriostatic mechanism and evaluated the in vivo inhibitory impact of caffeic acid-grafted chitosan self-assembled micelles loaded quercetin (CA-g-CS/QR) on avian Escherichia coli (E. coli). The findings indicate that the bactericidal mechanism of CA-g-CS/QR exhibits enhanced efficacy compared to QR alone, disrupting bacterial cell walls, disassembling biofilm structures, and impeding essential components necessary for bacterial growth. Following an avian E. coli attack in broilers, CA-g-CS/QR demonstrated the capacity to enhance the population of beneficial bacteria while concurrently decreasing harmful bacteria within the intestinal tract. Moreover, within 3 days of oral administration of CA-g-CS/QR, a significant decrease in Escherichia spp. count was evident, resulting in the restoration of broilers to a healthy state. CA-g-CS/QR proved to be a significant and more efficacious solution than QR alone for avian E. coli disease. Furthermore, CA-g-CS/QR displayed a broader distribution range and higher concentration within the body. Ten metabolites have been identified in the liver for both QR and CA-g-CS/QR. In conclusion, CA-g-CS/QR has demonstrated a notable capacity to enhance in vitro and in vivo bacterial inhibitory effects, providing foundation for the clinical application of QR in combating avian E. coli infections in broilers.

Investigation of the antibacterial activity of benziothiazolinone against Xanthomonas oryzae pv. oryzae

Plant pathogenic bacteria can cause numerous diseases for higher plants and result in severe reduction of crop yield. Introduction of new bactericides can always effectively control these plant diseases. Benziothiazolinone (BIT) is a novel fungicide registered in China for the control of plant fungal diseases, however, its anti-bacterial activity is not well studied. The results of activity tests showed that BIT exhibited stronger inhibitory activity against bacteria, particularly for Xanthomonas oryzae pv. oryzae (Xoo) (EC50 = 0.17 μg/mL), which was superior than that of the tested fungi in vitro. BIT also exhibited excellent protective and curative activity against rice bacterial leaf blight (BLB) caused by Xoo with the control efficacies of 71.37% and 91.64% at 600 μg/mL, respectively. After treatment with BIT, Xoo cell surface became wrinkled and the cell shape was distorted with extruding cellular content. It was also found that BIT decreased DNA synthesis and affected the biofilm formation and motility of Xoo cells. However, no significant change in the protein content was observed. Moreover, the results of quantitative real-time PCR also showed that expressions of several genes related to DNA synthesis, biofilm formation and motility of Xoo cells were down- or up-regulated, which further proved the anti-bacterial activity of BIT in influencing the biological properties of Xoo. Additionally, BIT also enhanced the activity of phenylalanine ammonia lyase (PAL), a plant defense enzyme. Taken together, benziothiazolinone might be served as an alternative candidate for the control of BLB.

Study on Mechanisms of Resistance to SDHI Fungicide Pydiflumetofen in Fusarium fujikuroi

Rice bakaenii disease (RBD) is a widespread and devastating disease mainly caused by Fusarium fujikuroi. Pydiflumetofen (Pyd) is a novel succinate dehydrogenase inhibitor (SDHI) with strong inhibitory activity against F. fujikuroi, but the mechanism of resistance to Pyd has not been well studied for this pathogen. Through fungicide adaption, a total of 12 Pyd-resistant mutants were obtained and the resistance level could be divided into three categories of high resistance (HR), moderate resistance (MR), and low resistance (LR) with resistance factors (RF) of 184.04-672.90, 12.63-42.49, and <10, respectively. Seven genotypes of point mutations in FfSdh genes (FfSdhBH248L, FfSdhBH248D, FfSdhBH248Y, FfSdhC2A83V, FfSdhC2H144Y, FfSdhDS106F, and FfSdhDE166K) were found in these mutants, among which genotype FfSdhBH248L and FfSdhC2A83V mutants showed HR, genotype FfSdhBH248D, FfSdhBH248Y, FfSdhC2H144Y, and FfSdhDE166K mutants showed MR, and genotype FfSdhDS106F mutants showed LR. Moreover, all the substitutions of amino acid point mutations including FfSdhBH248L/D/Y, FfSdhC2A83V,H144Y, and FfSdhDS106F,E166K conferring resistance to Pyd in F. fujikuroi were verified by protoplast transformation. Additionally, a positive cross-resistance was detected between Pyd and another SDHI fungicide penflufen, while no cross-resistance was detected between Pyd and phenamacril, prochloraz, azoxystrobin, carbendazim, or fludioxonil. Although pathogenicity of the mutants was increased compared with that of the wild-type parental strains, the mycelial growth rate and spore production levels of the resistant mutants were significantly decreased (P < 0.05), indicating significant fitness cost of resistance to Pyd in F. fujikuroi. Taken together, the risk of resistance to Pyd in F. fujikuroi might be moderate, and appropriate precautions against resistance development in natural populations should be taken into account when Pyd is used for the control of RBD.