Screening of core microorganisms in healthy and diseased peaches and effect evaluation of biocontrol bacteria (Burkholderia sp.)

Biological antagonists serve as the most important green alternatives to chemical fungicides, a class of microorganism that inhibits the growth of pathogenic fungi to reduce fruit incidence. In this paper, healthy and diseased peach fruit was selected for amplicon sequencing of the epiphytic microbiota on their surface to obtain a comprehensive understanding. Community structure, diversity and LefSe analysis were performed to screen Acetobacter, Muribaculaceae and Burkholderia as the core bacteria, Mycosphaerella, Penicillium and Alternaria as the core fungi, they showed significant differences and were highly enriched. Two strains fungi (Penicillium K3 and N1) and one strain antagonistic bacteria (Burkholderia J2) were isolated. The in intro test results indicated the bacterial suspension, fermentation broth and volatile organic compounds of antagonistic bacteria J2 were able to significantly inhibit pathogen growth. In vivo experiments, peach was stored at 28 °C for 6 days after different treatments, and samples were taken every day. It was found that Burkholderia J2 enhanced peach resistance by increasing the activities of antioxidant-related enzymes such as SOD, POD, PAL, PPO, GR, MDHAR, and DHAR. The results improved that Burkholderia J2 has great biocontrol potential and could be used as a candidate strain for green control of blue mold.

Eco-friendly Biosynthesis of Ag-NPs by Streptomyces griseus With Anti- Candida albicans and Antitumor Activity

BACKGROUND

The most significant sexually transmissible fungal disease, semen candidiasis, is caused by Candida albicans and impacts male reproductive potential. Actinomycetes are a group of microorganisms that could be isolated from various habitats and used for the biosynthesis of various nanoparticles with biomedical applications.

OBJECTIVE

Testing antifungal activity of biosynthesized Ag nanoparticles versus isolated C. albicans from semen as well as its anticancer activity versus the Caco-2 cell line.

METHODS

Screening 17 isolated actinomycetes for the biosynthesis of Ag nanoparticle biosynthesis. Characterization of biosynthesized nanoparticles, testing its anti-Candida albicans, and antitumor activity.

RESULTS

Streptomyces griseus was the isolate that identified silver nanoparticles using UV, FTIR, XRD and TEM. Biosynthesized nanoparticles have promising anti-Candida albicans with MIC (125 ± 0.8) µg/ml and accelerate apoptotic rate versus Caco-2 cells (IC50 = 7.30 ± 0.54 µg/ml) with minimal toxicity (CC50 = 142.74 ± 4.71 µg/ml) versus Vero cells.

CONCLUSION

Certain actinomycetes could be used for the biosynthesis of nanoparticles with successive antifungal and anticancer activity to be verified by in vivo studies.

Green synthesis and characterization of nanosilver derived from extracellular metabolites of potent Bacillus subtilis for antifungal and eco-friendly action against phytopathogen

The potent antagonist Bacillus isolated from the soil rhizosphere elucidated the highest antagonism against the phytopathogen Fusarium oxysporum f. sp. cumini and was identified as Bacillus subtilis strain JSD-RSCu-8D based on molecular recognition by 16S rRNA sequencing (NCBI Accession No. KT894724). Live Bacillus may not work as effectively against phytopathogen under unfavorable environmental conditions like temperature, humidity, or other abiotic stresses. The extracellular metabolites, obtained from culturing potent B. subtilis, were exploited for the creation of green nanosilver for proficient actions in a changing climate. The synthesized green nanosilver was illustrated for shape (spherical with 65.21 ± 3.71 nm under SEM), size (70.9 nm in PSA), purity (2.69 keV peak corresponded to the binding energy of silver under EDAX), and stability (44.2 mV as ZETA). The formation of green Ag-NPs from extracellular metabolites was confirmed by a comparative appraisal of the electromagnetic peak of the metabolite's functional groups, silver nitrate, and green nanoparticles in Fourier transform infrared spectroscopy. The novel mode of action of pathogen mycelium degradation was elucidated by the minimum inhibitory concentration (MIC) of green nanosilver as 40 µg Ag ml^-1 to diminish F. oxysporum (SEM morphology). The green nanosilver at 2 DAI renowned the leakage of sugars from mycelia of the cell membrane and defeated the activity of respiratory chain dehydrogenases, followed by lipid peroxidation and the highest leakage of proteins at 3 DAI on MIC. The in-vivo study might allow for novel insight to utilize green nanosilver at MIC (40 µg Ag ml^-1) as an eco-friendly and fungicide alternate way for antifungal action to demolish Fusarium wilt infection under harsh conditions.

Cellular uptake of chitosan and its role in antifungal action against Penicillium expansum

Chitosan has wide-spectrum antimicrobial activity but knowledge of its antifungal mechanism is still incomplete. In this study, transcriptome of Penicillium expansum upon chitosan treatment was analyzed by RNA-Seq. KEGG enrichment analysis revealed that endocytosis as well as other physiological pathways was regulated by chitosan treatment. Clathrin adaptor protein mu-subunit (PeCAM) gene, which encodes a protein associated with clathrin-dependent endocytosis, was up-regulated after chitosan treatment. Deletion of PeCAM resulted in changes of conidial, hyphal and colonial morphology. Confocal microscopy images of the distribution of fluorescein isothiocyanate-labeled chitosan confirmed cellular internalization of chitosan. However, deletion of PeCAM almost completely blocked uptake of chitosan into fungal cells and ΔPeCAM mutant exhibited less sensitivity to chitosan compared with wild type, suggesting that chitosan uptake is mediated by clathrin-dependent endocytosis and internalized chitosan also plays an important role in its antifungal activity. Collectively, our results provide a new insight into the antifungal mechanism of chitosan.

Sensitivity of food spoilage fungi to a smoke generator sanitizer

Smoke generator sanitizers are easy to handle and can access to hard-to-reach places. They are a promising alternative for controlling food and air borne fungi, which are known to cause losses in the bakery, meat, and dairy industries. Therefore, the present study aimed to evaluate the efficiency of a smoke generator sanitizer based on orthophenylphenol against ten fungal species relevant to food spoilage. The tests were carried out according to the norms by the French protocol NF-T-72281, with adaptations specific for disinfectants diffused in the air. The tests were performed in an enclosed room of approximately 32 m³. Aspergillus brasiliensis (ATCC 16404), Candida albicans (ATCC 10231), Aspergillus flavus (ATCC 9643), Aspergillus chevalieri (IMI 211382), Cladosporium cladosporioides (IMI 158517), Lichtheima corymbifera (CCT 4485), Mucor hiemalis (CCT 4561), Penicillium commune (CCT 7683), Penicillium polonicum (NGT 33/12), and Penicillium roqueforti (IMI 217568) were exposed to the smoke generator sanitizer for 7 h. The product was efficient against C. albicans and C. cladosporioides, although it was unable to reduce 4 log of the other tested species. The variable sensitivity of the fungal species to the sanitizer emphasizes the importance of confronting a target microorganism (causing problems in a specific food industry) with the sanitizer aiming to control it and obtain satisfactory results in hygiene programs.