Multi-Omics Analysis Reveals that the Antimicrobial Kasugamycin Potential Targets Nitrate Reductase in Didymella segeticola to Achieve Control of Tea Leaf Spot

In Addition to Damaging the Plasma Membrane, Phenolic Monoterpenoid Carvacrol Can Bind to the Minor Groove of DNA of Phytopathogenic Fungi to Potentially Control Tea Leaf Spot Caused by Lasiodiplodia theobromae

Carvacrol expresses a wide range of biological activities, but the studies of its mechanisms focused on bacteria, mainly involving the destruction of the plasma membrane. In this study, carvacrol exhibited strong activities against several phytopathogenic fungi and demonstrated a novel antifungal mechanism against Lasiodiplodia theobromae. RNA sequencing indicated that many genes of L. theobromae hyphae were predominately induced by carvacrol, particularly those involved in replication and transcription. Hyperchromic, hypsochromic, and bathochromic effects in the UV-visible absorption spectrum were observed following titration of calf thymus DNA (ctDNA) and carvacrol, which indicated the formation of a DNA-carvacrol complex. Circular dichroism (CD) spectroscopy indicated that the response of DNA to carvacrol was similar to that of 4',6-diamidino-2-phenylindole (DAPI) but different from that of ethidium bromide (EB), implying the ionic bonds between carvacrol and ctDNA. Fluorescence spectrum (FS) analysis indicated that carvacrol quenched the fluorescence of double-stranded DNA (dsDNA) more than single-stranded DNA, indicating that carvacrol mainly bound to dsDNA. A displacement assay showed that carvacrol reduced the fluorescence intensity of the DNA-DAPI complex through competition with DAPI, but this did not occur for DNA-EB. The FS assay revealed that carvacrol bound to the AAA sequence on the minor groove of ds-oligonucleotides. The hydroxyl of carvacrol was verified to bind to ctDNA through a comparative test in which structural analogs of carvacrol, including thymol and 4-ethyl-1,2-dimethyl, were analyzed. The current study indicated carvacrol can destruct plasma membranes and bind to the minor groove of DNA, inhibiting fungal proliferation by disturbing the stability of dsDNA.

The Probiotic Potential and Metabolite Characterization of Bioprotective Bacillus and Streptomyces for Applications in Animal Production

Probiotics are increasingly recognized for their potential in managing bacterial challenges in animal production. This study aimed to evaluate the probiotic potential of Bacillus and Streptomyces strains, specifically their bioprotective ability against Salmonella. In agar inhibition assays, these bacteria supported Salmonella-inhibition zones, ranging from 2.5 ± 0.5 to 6.3 ± 2.0 mm. Analyses of antimicrobial metabolites revealed their capacity to produce compounds with anti-Salmonella properties, except for Bacillus subtilis MLB2. When Salmonella was exposed to lyophilized metabolites, inhibition occurred in both liquid (at concentrations between 250 and 500 g/L) and solid cultures (at 500 g/L). To confirm their probiotic potential, the S. griseus and Bacillus strains underwent evaluations for antimicrobial resistance, bile salt tolerance, auto- and co-aggregation, pH resistance, and their ability to adhere to and inhibit Salmonella in Caco-2 cells. These assessments confirmed their probiotic potential. The probiotic strains were further encapsulated and subjected to simulated swine and poultry digestion. They demonstrated survival potential through the gastrointestinal tract and significantly reduced the Salmonella population. Thus, these strains exhibit considerable promise for producing biotechnological products aimed at controlling Salmonella in animal production. This approach ensures the health and hygiene of farming facilities, mitigates the spread of zoonotic bacteria, and contributes positively to public health.

Nitrate reductase is required for sclerotial development and virulence of Sclerotinia sclerotiorum

Sclerotinia sclerotiorum, the causal agent of Sclerotinia stem rot (SSR) on more than 450 plant species, is a notorious fungal pathogen. Nitrate reductase (NR) is required for nitrate assimilation that mediates the reduction of nitrate to nitrite and is the major enzymatic source for NO production in fungi. To explore the possible effects of nitrate reductase SsNR on the development, stress response, and virulence of S. sclerotiorum, RNA interference (RNAi) of SsNR was performed. The results showed that SsNR-silenced mutants showed abnormity in mycelia growth, sclerotia formation, infection cushion formation, reduced virulence on rapeseed and soybean with decreased oxalic acid production. Furthermore SsNR-silenced mutants are more sensitive to abiotic stresses such as Congo Red, SDS, H₂O₂, and NaCl. Importantly, the expression levels of pathogenicity-related genes SsGgt1, SsSac1, and SsSmk3 are down-regulated in SsNR-silenced mutants, while SsCyp is up-regulated. In summary, phenotypic changes in the gene silenced mutants indicate that SsNR plays important roles in the mycelia growth, sclerotia development, stress response and fungal virulence of S. sclerotiorum.

Evaluation of kasugamycin as a chiral selector in capillary electrophoresis

The discovery of novel chiral selectors always fascinates us. This work describes the chiral separation performances of a new chiral selector (kasugamycin, KAS) in capillary electrophoresis (CE) for six pairs of stereoisomers, including ephedrine and pseudoephedrine, quinine and quinidine, cinchonine and cinchonidine, and amlodipine, promethazine and ofloxacin enantiomers. Kasugamycin, an aminoglycoside antibiotic in agriculture, shows significant biological activity against rice blast with low toxicity. As it turns out, this new chiral selector possesses good CE compatibility and stereoselectivity towards model analytes. In this work, we systematically investigated several separation parameters including kasugamycin concentration, buffer pH, separation voltage and the composition of the buffer solution. A detailed discussion about the chiral recognition mechanism was made based on Statistical Product and Service Solution (SPSS) analysis, NMR experiments (1D and 2D) and molecular modeling. This is the first time that kasugamycin is utilized as a chiral selector in CE, and the development of new chiral selectors from agricultural or veterinary antibiotics deserves more attention.

Integrated Transcriptome and Proteome Analysis Reveals that the Antimicrobial Griseofulvin Targets Didymella segeticola Beta-Tubulin to Control Tea Leaf Spot

Because effective control measures are lacking, tea leaf spot caused by Didymella segeticola results in huge tea (Camellia sinensis) production losses on tea plantations in Guizhou Province, southwestern China. Screening for natural antimicrobial agents with higher control effects against this pathogen and studying their modes of action may contribute to disease management. Here, Penicillium griseofulvum-derived antimicrobial griseofulvin (GSF) can inhibit the hyphal growth of D. segeticola strain GZSQ-4, with a half-maximal effective concentration of 0.37 μg/ml in vitro and a higher curative efficacy at a lower dose of 25 μg/ml for detached tea twigs. GSF induces deformed and slightly curly hyphae with enlarged ends, with protoplasts agglutinated in the hyphae, and higher numbers of hyphal protuberances. GSF alters hyphal morphology and the subcellular structure's order. The integrated transcriptome and proteome data revealed that the transport of materials in cells, cellular movement, and mitosis were modulated by GSF. Molecular docking indicated that beta-tubulin was the most potent target of GSF, with a binding free energy of -13.59 kcal/mol, and microscale thermophoresis indicated that the dissociation constant (Kd) value of GSF binding to beta-tubulin 1, compared with beta-tubulin 2, was significantly lower. Thus, GSF potentially targets beta-tubulin 1 to disturb the chromosomal separation and fungal mitosis, thereby inhibiting hyphal growth.

Zeolitic Imidazole Framework-90-Based Pesticide Smart-Delivery System with Enhanced Antimicrobial Performance

Multimodal antimicrobial technology is regarded as a promising strategy for controlling plant diseases because it enhances antimicrobial efficacy by blocking multiple pesticide-resistance pathways. In this work, a pH-responsive multimodal antimicrobial system was constructed based on ZIF-90 for the controlled release of kasugamycin (KSM). A series of physicochemical characterizations confirmed the successful fabrication of ZIF-90-KSM. The results indicated that the loading capacity of ZIF-90-KSM for KSM was approximately 6.7% and that the ZIF-90 nanocarriers could protect KSM against photodegradation effectively. The acid pH at the site of disease not only decompose the Schiff base bonds between KSM and ZIF-90, but also completely dissolved the nanocarriers. The simultaneous release of KSM and Zn²⁺ ions was able to achieve multimodal antimicrobial functions during disease occurs. A bioactivity survey indicated that ZIF-90-KSM had superior fungicidal activity and longer duration against Magnaporthe oryzae than KSM aqueous solution. In addition, the phytotoxicity assessment of ZIF-90-KSM on rice plants did not reveal any adverse effects. Therefore, ZIF-90-KSM prepared by Schiff base reaction has great potential for achieving synergistic antifungal functions and provides an eco-friendly approach to manage rice diseases.