Antifungal activity and genomic characterization of the biocontrol agent Bacillus velezensis CMRP 4489

Antimicrobial Potential of Secalonic Acids from Arctic-Derived Penicillium chrysogenum INA 01369

In this study, two compounds have been isolated from the Arctic-derived fungus Penicillium chrysogenum INA 13460. Structural elucidation, performed using 2D NMR and HR-ESIMS data, has identified the compounds as stereoisomers of secalonic acids, dimeric tetrahydroxanthones. The absolute configurations of these stereoisomers have been determined through conformational NMR analysis and circular dichroism spectroscopy. The antimicrobial activity of secalonic acids D and F has been evaluated against a diverse range of microorganisms, including Gram-positive multidrug-resistant Staphylococcus aureus, Gram-negative Escherichia coli ATCC 25922, Pseudomonas aeruginosa ATCC 27853, the phytopathogen Pectobacterium carotovorum VKM-B1247, and the fungi Fusarium oxysporum VKPM F 890, Aspergillus fumigatus VKM F-37, and A. niger ATCC 16404. Genomic and chemical analyses further support P. chrysogenum INA 13460 as a promising natural source for antimicrobial drug discovery and biological control applications.

New Ground in Antifungal Discovery and Therapy for Invasive Fungal Infections: Innovations, Challenges, and Future Directions

This review explores current advancements and challenges in antifungal therapies amid rising fungal infections, particularly in immunocompromised patients. We detail the limitations of existing antifungal classes-azoles, echinocandins, polyenes, and flucytosine-in managing systemic infections and the urgent need for alternative solutions. With the increasing incidence of resistance pathogens, such as Candida auris and Aspergillus fumigatus, we assess emerging antifungal agents, including Ibrexafungerp, T-2307, and N'-Phenylhydrazides, which target diverse fungal cell mechanisms. Innovations, such as nanoparticles, drug repurposing, and natural products, are also evaluated for their potential to improve efficacy and reduce resistance. We emphasize the importance of novel approaches to address the growing threat posed by fungal infections, particularly for patients with limited treatment options. Finally, we briefly examine the potential use of artificial intelligence (AI) in the development of new antifungal treatments, diagnoses, and resistance prediction, which provides powerful tools in the fight against fungal pathogens. Overall, we highlight the pressing need for continued research to advance antifungal treatments and improve outcomes for high-risk populations.

A rice rhizosphere plant growth-promoting Streptomyces corchorusii isolate antagonizes Magnaporthe oryzae and elicits defense responses in rice

AIMS

Rice blast, caused by Magnaporthe oryzae, is one of the most devastating diseases of rice (Oryza sativa L.). The aim of this study was to investigate the biocontrol potential of rice rhizosphere actinomycetes against M. oryzae Guy 11, and elucidate the antagonistic mechanisms.

METHODS AND RESULTS

An isolate characterized as a Streptomyces corchorusii strain (Sc75) using the 16S rRNA gene exhibited superior antifungal activity. Sc75 had an inhibitory effect of 69.25% ± 0.15% against M. oryzae and broad antifungal activity on other fungal plant pathogens in the dual culture assay. Its cell-free culture filtrate inhibited fungal growth and reduced mycelial mass. Also, the ethyl acetate crude extract completely inhibited conidia germination and appressoria formation on the hydrophobic coverslips and detached leaf at a concentration of 20 mg/ml. Its volatile organic compounds (VOCs) suppressed fungal growth by 98.42%. GC-MS analysis of the VOCs identified butanoic acid, 2-methyl-, methyl ester; di-tert-butyl peroxide; furan, 2-pentyl-; and undecanoic acid, 10-methyl-, methyl ester as the main components. In the greenhouse experiment, the disease severity was reduced and growth promotion was evident. Molecular investigation revealed that Sc75 upregulated defense-related genes involved in the synthesis of jasmonic acid, salicylic acid signaling pathway, and led to callose deposition and ROS production in the leaves. Finally, Sc75 produced hydrolytic enzymes, siderophore, indole acetic acid, gibberellic acid, phosphate solubilization, and 1-aminocyclopropane-1-carboxylate deaminase.

CONCLUSIONS

The rice rhizosphere soil harbors actinomycetes that can be explored as biocontrol agents against fungal pathogens such as M. oryzae. The isolate Sc75 had superior antifungal activity against M. oryzae and other selected plant pathogenic fungi. It showed remarkable antagonistic activity through direct antibiosis, production of VOCs, antifungal metabolites in the culture filtrates and crude extracts, and produced enzymes. In addition, the isolate promoted plant growth, reduced rice blast disease index in the greenhouse experiment, and elicited defense-related responses. Sc75 is a promising candidate for future exploration as a biofungicide and a biofertilizer.

Genomic Insights into the Bactericidal and Fungicidal Potential of Bacillus mycoides b12.3 Isolated in the Soil of Olkhon Island in Lake Baikal, Russia

The dispersal of plant pathogens is a threat to the global economy and food industry which necessitates the need to discover efficient biocontrol agents such as bacteria, fungi, etc., inhibiting them. Here, we describe the Bacillus mycoides strain b12.3 isolated from the soil of Olkhon Island in Lake Baikal, Russia. By applying the co-cultivation technique, we found that the strain inhibits the growth of plant pathogens, such as the bacteria Xanthomonas campestris, Clavibacter michiganensis, and Pectobacterium atrospecticum, as well as the fungus Alternaria solani. To elucidate the genomic fundament explaining these activities, we leveraged next-generation whole-genome sequencing and obtained a high-quality assembly based on short reads. The isolate bore seven known BGCs (biosynthetic gene clusters), including those responsible for producing bacillibactin, fengycin, and petrobactin. Moreover, the genome contained insecticidal genes encoding for App4Aa1, Tpp78Ba1, and Spp1Aa1 toxins, thus implicating possible pesticidal potential. We compared the genome with the 50 closest assemblies and found that b12.3 is enriched with BGCs. The genomic analysis also revealed that genomic architecture corresponds to the experimentally observed activity spectrum implying that the combination of produced secondary metabolites delineates the range of inhibited phytopathogens Therefore, this study deepens our knowledge of the biology and ecology of B. mycoides residing in the Lake Baikal region.

Enhanced Antifungal Efficacy of Validamycin A Co-Administered with Bacillus velezensis TCS001 against Camellia anthracnose

Anthracnose, a fungal disease harming fruit trees and crops, poses a threat to agriculture. Traditional chemical pesticides face issues like environmental pollution and resistance. A strategy combining low-toxicity chemicals with biopesticides is proposed to enhance disease control while reducing chemical use. Our study found that mixing validamycin A (VMA) and Bacillus velezensis TCS001 effectively controlled anthracnose in Camellia oleifera. The combination increased antifungal efficacy by 65.62% over VMA alone and 18.83% over TCS001 alone. It caused pathogen deformities and loss of pathogenicity. Transcriptomic analysis revealed that the mix affected the pathogen's metabolism and redox processes, particularly impacting cellular membrane functions and inducing apoptosis via glycolysis/gluconeogenesis. In vivo tests showed the treatment activated C. oleifera's disease resistance, with a 161.72% increase in polyphenol oxidase concentration in treated plants. This research offers insights into VMA and TCS001's mechanisms against anthracnose, supporting sustainable forestry and national edible oil security.

Evaluation of Bacillus isolates as a biological control agents against soilborne phytopathogenic fungi

Pesticides, used in agriculture to control plant diseases, pose risks to the environment and human health. To address this, there's a growing focus on biocontrol, using microorganisms instead of chemicals. In this study, we aimed to identify Bacillus isolates as potential biological control agents. We tested 1574 Bacillus isolates for antifungal effects against pathogens like Botrytis cinerea, Fusarium solani, and Rhizoctonia solani. Out of these, 77 isolates formed inhibition zones against all three pathogens. We then investigated their lytic enzyme activities (protease, chitinase, and chitosanase) and the production of antifungal metabolites (siderophore and hydrogen cyanide). Coagulase activity was also examined to estimate potential pathogenicity in humans and animals. After evaluating all mechanisms, 19 non-pathogenic Bacillus isolates with significant antifungal effects were chosen. Molecular identification revealed they belonged to B. subtilis (n = 19) strains. The 19 native Bacillus strains, demonstrating strong antifungal effects in vitro, have the potential to form the basis for biocontrol product development. This could address challenges in agricultural production, marking a crucial stride toward sustainable agriculture.

Biocontrol in built environments to reduce pathogen exposure and infection risk

The microbiome of the built environment comprises bacterial, archaeal, fungal, and viral communities associated with human-made structures. Even though most of these microbes are benign, antibiotic-resistant pathogens can colonize and emerge indoors, creating infection risk through surface transmission or inhalation. Several studies have catalogued the microbial composition and ecology in different built environment types. These have informed in vitro studies that seek to replicate the physicochemical features that promote pathogenic survival and transmission, ultimately facilitating the development and validation of intervention techniques used to reduce pathogen accumulation. Such interventions include using Bacillus-based cleaning products on surfaces or integrating bacilli into printable materials. Though this work is in its infancy, early research suggests the potential to use microbial biocontrol to reduce hospital- and home-acquired multidrug-resistant infections. Although these techniques hold promise, there is an urgent need to better understand the microbial ecology of built environments and to determine how these biocontrol solutions alter species interactions. This review covers our current understanding of microbial ecology of the built environment and proposes strategies to translate that knowledge into effective biocontrol of antibiotic-resistant pathogens.

Adding Metal Ions to the Bacillus mojavensis D50 Promotes Biofilm Formation and Improves Ability of Biocontrol

Bacillus mojavensis D50, a biocontrol strain, is used to prevent and treat the fungal plant pathogen Botrytis cinerea. Bacillus mojavensis D50's biofilms can affect its colonization; thus, the effects of different metal ions and culture conditions on biofilm formation were determined in this study. The results of medium optimization showed that Ca²⁺ had the best ability to promote biofilm formation. The optimal medium composition for the formation of biofilms contained tryptone (10 g/L), CaCl₂ (5.14 g/L), and yeast extract (5.0 g/L), and the optimal fermentation conditions included pH 7, a temperature of 31.4 °C, and a culture time of 51.8 h. We found that the antifungal activity and abilities to form biofilms and colonize roots were improved after optimization. In addition, the levels of expression of the genes luxS, SinR, FlhA, and tasA were up-regulated by 37.56-, 2.87-, 12.46-, and 6.22-fold, respectively. The soil enzymatic activities which related biocontrol-related enzymes were the highest when the soil was treated by strain D50 after optimization. In vivo biocontrol assays indicated that the biocontrol effect of strain D50 after optimization was improved.