VIT-CMJ2: Endophyte of Agaricus bisporus in Production of Bioactive Compounds

Xenomyrothecium tongaense PTS8: a rare endophyte of Polianthes tuberosa with salient antagonism against multidrug-resistant pathogens

Introduction

Endophytes refer to microorganisms residing within the endosphere of plants, particularly perennials, without inflicting noticeable injury or inducing obvious morphological variations to their host plant or host organism. Endophytic fungi, although often overlooked microorganisms, have garnered interest due to their significant biological diversity and ability to produce novel pharmacological substances.

Methods

In this study, fourteen endophytic fungi retrieved were from the stem of the perennial plant Polianthes tuberosa of the Asparagaceae family. These fungal crude metabolites were tested for antagonistic susceptibility to Multi-Drug Resistant (MDR) pathogens using agar well diffusion, Minimum Inhibitory Concentration (MIC), and Minimum Bactericidal Concentration (MBC) assays. The chequerboard test was used to assess the synergistic impact of active extract.

Results and discussion

In early antibacterial screening using the Agar plug diffusion test, three of fourteen endophytes demonstrated antagonism against Methicillin-resistant Staphylococcus aureus (MRSA) and Vancomycin-resistant Enterococcus (VRE). Three isolates were grown in liquid medium and their secondary metabolites were recovered using various organic solvents. Eight extracts from three endophytic fungi displayed antagonism against one or more human pathogens with diameters ranging from 11 to 24 mm. The highest antagonistic effect was obtained in ethyl acetate extract for PTS8 isolate against two MRSA (ATCC 43300, 700699) with 20 ± 0.27 and 22 ± 0.47 mm zones of inhibition, respectively, among different solvent extracts. The extract had MICs of 3.12 ± 0.05 and 1.56 ± 0.05 μg/mL, and MBCs of 50 ± 0.01 and 12.5 ± 0.04 μg/mL, respectively. Antagonism against VRE was 18 ± 0.23 mm Zone of Inhibition (ZOI) with MIC and MBC of 6.25 ± 0.25 and 25 ± 0.01 μg/mL. When ethyl acetate extract was coupled with antibiotics, the chequerboard assay demonstrated a synergistic impact against MDR bacteria. In an antioxidant test, it had an inhibitory impact of 87 ± 0.5% and 88.5 ± 0.5% in 2,2-Diphenyl-1-Picrylhydrazyl and reducing power assay, respectively, at 150 μg/mL concentration. PTS8 was identified as a Xenomyrothecium tongaense strain by 18S rRNA internal transcribed spacer (ITS) sequencing. To our insight, it is the foremost study to demonstrate the presence of an X. tongaense endophyte in the stem of P. tuberosa and the first report to study the antibacterial efficacy of X. tongaense which might serve as a powerful antibacterial source against antibiotic-resistant human infections.

Study of growth-improving and sporophore-inducing endobacteria isolated from Pleurotus pulmonarius

Several Pleurotus species (oyster mushrooms) are commercially cultivated in India owing to the favorable tropical agro-climatic conditions. However, there are only a few studies on the microbiome of mushrooms, especially oyster mushrooms. The aim of this study was to assess the effect of endobacteria on mycelial growth, spawning, sporophore development, and proximate composition of P. pulmonarius. We isolated several bacterial strains from the sporophores of P. pulmonarius and assessed the in vitro production of indole acetic acid, ammonia, and siderophores. The selected bacteria were individually supplemented with spawn, substrate, or both for sporophore production. Three of 130 isolates were selected as mycelial growth-promoting bacteria in both solid and submerged fermentation. These bacterial isolates were identified through Gram staining, biochemical characterization, and 16S rRNA sequencing. Isolate PP showed 99.24% similarity with Priestia paraflexa, whereas isolates PJ1 and PJ2 showed 99.78% and 99.65% similarities, respectively, with Rossellomorea marisflavi. The bacterial supplementation with spawn, substrate, or both, increased the biological efficiency (BE) and nutrient content of the mushrooms. The bacterial supplementation with substrate augmented BE by 64.84%, 13.73%, and 27.13% using PJ2, PP, and PJ1, respectively; under similar conditions of spawn supplementation, BE was increased by 15.24%, 47.30%, 48.10%, respectively. Overall, the supplementation of endobacteria to improve oyster mushroom cultivation may open a new avenue for sustainable agricultural practices in the mushroom industry.

Isolation of Endophytic Fungus from Leaves of Uncaria cordata (Lour.) Merr and Antibacterial Activity Against Propionibacterium acnes and Escherichia coli

Uncaria cordata (Lour). Merr (akar kaik-kaik) is one of the medicinal plants used as antibacterial because it contains bioactive compounds that can inhibit the growth of microorganisms. The plant is one of the sources of endophyte fungal isolates that can be developed as an alternative to producing antibacterial compounds. This research aimed to isolate the endophytic fungus from the leaves of U. cordata and know the antibacterial activity against Propionibacterium acnes and Escherichia coli by disc diffusion. The Fungi that were isolated from the leaves of U. cordata were 17 isolates. The isolates were continued for antibacterial activity testing: IFED 1 (Nigrospora sp.), IFED 2 (Aspergillus sp.), IFED 3 (Fusarium sp.), and IFED 4, whose genus was unknown. The results obtained were fungal isolates IFED 1 to IFED 4 had activity in inhibiting the growth of P. acnes with moderate category (18.16 mm) and weak categories (6.21, 6.16, and 6.68 mm) and in E. coli with moderate category (14.56 mm) and weak categories (6.53, 6.71, and 7.23 mm). The results of One-Way ANOVA and Tukey's test showed a significant difference (p <0.05) between the diameter of the inhibition zone with the type of endophytic fungus supernatant isolated from the leaves of U. cordata. The best isolate of endophytic fungi inhibiting P. acnes and E. coli bacteria was IFED 1 (Nigrospora sp).

Antibacterial Compounds from Mushrooms: A Lead to Fight ESKAPEE Pathogenic Bacteria?

Infectious diseases are among the greatest threats to global health in the 21st century, and one critical concern is due to antibiotic resistance developed by an increasing number of bacterial strains. New resistance mechanisms are emerging with many infections becoming more and more difficult if not impossible to treat. This growing phenomenon not only is associated with increased mortality but also with longer hospital stays and higher medical costs. For these reasons, there is an urgent need to find new antibiotics targeting pathogenic microorganisms such as ESKAPEE bacteria. Most of currently approved antibiotics are derived from microorganisms, but higher fungi could constitute an alternative and remarkable reservoir of anti-infectious compounds. For instance, pleuromutilins constitute the first class of antibiotics derived from mushrooms. However, macromycetes still represent a largely unexplored source. Publications reporting the antibacterial potential of mushroom extracts are emerging, but few purified compounds have been evaluated for their bioactivity on pathogenic bacterial strains. Therefore, the aim of this review is to compile up-to-date data about natural products isolated from fruiting body fungi, which significantly inhibit the growth of ESKAPEE pathogenic bacteria. When available, data regarding modes of action and cytotoxicity, mandatory when considering a possible drug development, have been discussed in order to highlight the most promising compounds.

Cryopreservation at -75°C of Agaricus subrufescens on wheat grains with sucrose

Agaricus subrufescens is a basidiomycete which is studied because of its medicinal and gastronomic importance; however, less attention has been paid to its preservation. This study aimed to evaluate the effect of sucrose addition to substrate and cryotube on the viability of Agaricus subrufescens cryopreserved at −20 °C and at −75 °C for one and two years. Zero, 10% or 20% sucrose was added to potato dextrose agar or wheat grain. The mycelia were cryopreserved in the absence of cryoprotectant or with sucrose solutions at 15%, 30% or 45%. After one or two years at −75 °C or at −20 °C, mycelia were thawed and evaluated about viability, initial time of growth, colony diameter and genomic stability. Cryopreservation at −20 °C is not effective to keep mycelial viability of this fungus. Cryopreservation at −75 °C is effective when sucrose is used in substrates and/or cryotubes. Without sucrose, cryopreservation at −75 °C is effective only when wheat grains are used. Physiological characteristic as mycelial colony diameter is negatively affected when potato dextrose agar is used and unaffected when wheat grain is used after two-year cryopreservation at −75 °C. The fungus genome does not show alteration after two-year cryopreservation at −75 °C.