Broad-Spectrum Antimicrobial Action of Cell-Free Culture Extracts and Volatile Organic Compounds Produced by Endophytic Fungi Curvularia Eragrostidis

Abstract

Endophytes are the mutualistic microorganisms that reside within the host plant and promote plant growth in adverse conditions. Plants and their endophytes are engaged in a symbiotic relationship that enables endophytes to access bioactive genes of the ethnomedicinal plants, and, as a result, endophytes are constantly addressed in the sector of pharmaceuticals and agriculture for their multidomain bio-utility. The gradual increase of antimicrobial resistance can be effectively countered by the endophytic metabolites. In these circumstances, in the present investigation, endophytic Curvularia eragrostidis HelS1 was isolated from an ethnomedicinally valuable plant Helecteris isora from East India’s forests. The secondary volatile and non-volatile metabolites are extracted from HelS1 and are found to be effective broad-spectrum antimicrobials. A total of 26 secondary metabolites (9 volatiles and 17 non-volatiles) are extracted from the isolate, which exhibits effective antibacterial [against six Gram-positive and seven Gram-negative pathogens with a minimum inhibitory concentrations (MIC) value ranging from 12.5 to 400 μg ml–1] and antifungal (against seven fungal plant pathogens) activity. The secondary metabolite production was optimised by one variable at a time technique coupled with the response surface methodology. The results revealed that there was a 34% increase in antibacterial activity in parameters with 6.87 g L–1 of fructose (as a carbon source), 3.79 g L–1 of peptone (as a nitrogen source), pH 6.75, and an inoculation period of 191.5 h for fermentation. The volatile metabolite production was also found to be optimum when the medium was supplemented with yeast extract and urea (0.2 g L–1) along with dextrose (40 g L–1). Amongst extracted volatile metabolites, 1-H-indene 1 methanol acetate, tetroquinone, N, N-diphenyl-2-nitro-thio benzamide, Trans 1, 2-diethyl-trans-2-decalinol, naphthalene, and azulene are found to be the most effective. Our investigation opens up opportunities in the sector of sustainable agriculture as well as the discovery of novel antimicrobials against dreadful phyto and human pathogens.

Antifungal activity of volatile and non-volatile metabolites of endophytes of Chloranthus elatior Sw.

“…These endophytes emitted maximum VOCs in modified culture media with potato dextrose agar prepared from instantly smashed potatoes, along with yeast extract and additional salts. Another endophytic fungus, Curvularia eragrostidis HelS1, an isolate of Helicteres isora , synthesizes a broad spectrum of volatile and non-volatile metabolites with a wide range of antibacterial and antifungal activity ( Santra and Banerjee, 2022c ).…”

Antifungal activity of bio-active cell-free metabolites and volatile organic compounds (VOCs) synthesised by endophytic fungal isolates of Garden Nasturtium

“…Disruption of the central carbohydrate mechanism as a result of blockage of the most three physiologically active enzymes is one of the prime causes of anticandidal activity of the metabolites. The blocking of valuable enzymes are a popular mode of action for endophyte-originated metabolites with antimicrobial potentialities [34][35] .…”

“…54 . VOCs are useful in post-harvest disease management, protection of standing crops, or even in improving the shelf life of cash crops 34 . In most cases, VOCs interact with the cell wall and cell membrane of phytopathogens, decreasing their integrity and increasing the permeability of their plasma membrane, leading to leakage of soluble proteins and UV (260 nm) active substances 55 .…”

Draft genome sequence of endophytic fungus Talaromyces purpureogenus strain YAFEF302, isolated from Juglans sigillata

“…A tissue grinder was used to grind the bark, after which sterile water was added to obtain a slurry. Finally, the bark slurry was further diluted and spread onto modified potato dextrose agar (PDA) ( 12 ) with 100 µg/mL ampicillin, kanamycin, and streptomycin, respectively. After 4 days of incubation (28°C), single colonies were transferred to fresh PDA medium.…”