Fungal bioremediation is a promising approach to remove heavy-metal from contaminated water. Present study examined the ability of an earthworm gut fungus Trichoderma brevicompactum QYCD-6 to tolerate and remove both individual and multi-metals. The minimum inhibitory concentration (MIC) of heavy metals [Cu(II), Cr(VI), Cd(II) and Zn(II)] against the fungus was ranged 150–200 mg L⁻¹ on composite medium, and MIC of Pb(II) was the highest with 1600 mg L⁻¹ on potato dextrose (PD) medium. The Pb(II) presented the highest metal removal rate (97.5%) which mostly dependent on bioaccumulation with 80.0%, and synchronized with max biomass (6.13 g L⁻¹) in PD medium. However, on the composite medium, the highest removal rate was observed for Cu(II) (64.5%). Cellular changes in fungus were reflected by TEM analysis. FTIR and solid-state NMR analyses indicated the involvement of different functional groups (amino, carbonyl, hydroxyl, et al.) in metallic biosorption. These results established that the earthworm-associated T. brevicompactum QYCD-6 was a promising fungus for the remediation of heavy-metal wastewater.

Background: Actinomycetes are important microbes, and they are very important for developing active substances for useful drugs. Actinomycetes are numerous inhabitants, and they are widely distributed in the nest of fungus-growing termites. Previously, we isolated and purified numerous actinomycetes from the combs of Odontotermes formosanus and obtained a variety of valuable natural products. Results: Here, we isolated and purified actinomycetes from fungus-growing termite Odontotermes formosanus using medium-based cultures. Among the eight media tested, M7 and I-HV media were found suitable for isolating actinomycetes. Further, 84 actinomycetes, including 79 Streptomyces isolates, were isolated and purified from O. formosanus and its combs, which belong to four genera (Streptomyces, Kribbella, Amycolatopsis, and Cellulosimicrobium). Then, the type and quantity of actinomycetes were positively correlated with the activity range of termites. Twenty-two actinomycetes strains showed antimicrobial activities. Among them, the BYF18, BYF48, BYF70, and BYF106 strains exhibited antifungal activities against five pathogenic fungi, with zone of inhibition (ZOI) values ranging from 3 to 21 mm. Grincamycin N was isolated and purified from the metabolites of Streptomyces lannensis (BYF106), and it displayed antibacterial activities against Staphylococcus aureus (ZOI = 13.82 ± 0.52 mm) and Micrococcus tetragenus (ZOI = 17.6 ± 0.5 mm) (gentamycin sulfate, as the positive control, had ZOI values of 19.9 ± 0.5 mm and 30.83 ± 0.75 mm, against S. aureus and M. tetragenus, respectively). Conclusions: Our results confirmed that the actinomycetes associated with O. formosanus are important sources of new active substances.

The phylogenetic diversity of fungi isolated from the Odontotermes formosanus was investigated by dilution-plate method, combined with morphological characteristics and 5.8S rDNA sequencing. Thirty-nine fungi were isolated and purified from O. formosanus, which were belonging to two phyla and four classes (Sordariomycetes, Dothideomycetes, Eurotiomycetes, Agaricomycetes). Furthermore, nine bacterial 16S rRNA sequences were obtained from total fungal genomic DNA. All bacterial symbionts were segmented into four genera: Bacillus, Methylobacterium, Paenibacillus, and Trabulsiella. The antimicrobial activities of all endophytic fungi extracts were tested by using the filter paper method against Escherichia coli (ATCC 8739), Bacillus subtilis (ATCC 6633), Staphylococcus aureus (ATCC 6538), and Canidia albicans (ATCC 10231). The results exhibited that 25 extracts (64%) exhibited antibacterial activity against at least one of the tested bacterial strains. Furthermore, the secondary metabolites 1 [5-hydroxyramulosin (1a):biatriosporin M (1b) = 2:1] from the Pleosporales sp. BYCDW4 exhibited potent antimicrobial activities against E. coli, C. albicans, B. subtilis, and S. aureus with the inhibition zone diameter (IZD) of 13.67, 14.33, 12.17, and 11.33 mm, respectively, which were comparable with those of the positive control. 1-(2,5-Dihydroxyphenyl)-3-hydroxybutan-1-one (2) from the Microdiplodia sp. BYCDW8 showed medium inhibitory activities against B. subtilis and S. aureus, with the IZD range of 8.32–9.13 mm. In conclusion, the study showed the diversity of insect symbionts could be expected to develop the resource of new species and antibiotics.

Twenty-one strains of termite-associated actinomycetes were tested for their activities against three bacteria. The results showed that nine strains showed bacteriostatic activities against at least one tested bacterium, and the actinomycete YH01, which was isolated from the body surface of the queen of Odontotermes formosanus, had potent antibacterial activity. The YH01 was further identified as Streptomyces davaonensis. Two metabolites roseoflavin (1) and 8-methylamino-8-demethyl-d-riboflavin (2) were isolated and purified from S. davaonensis YH01. Their structures were determined by NMR, MS, and the related literature. The metabolite 1 showed strong inhibition activities against Bacillus subtilis (MIC = 1.56 μg/mL) and Staphylococcus aureus (MIC = 3.125 μg/mL), which were comparable to referenced gentamycin sulfate, with MIC values of 1.56 and 1.56 μg/mL, respectively. Furthermore, the anti-MRSA potential of compound 1 was determined against nine kinds of MRSA strains, with inhibition zones in the ranges of 12.7–19.7 mm under a concentration of 15 μg/6 mm discs and 18.3–22.7 mm under a concentration of 30 μg/6 mm discs. However, metabolite 1 had no inhibitory effect on Gram-negative bacteria. These results suggested that roseoflavin produced by YH01 holds promise for use against Gram-positive bacteria, especially to MRSA.

Three chemical epigenetic modifiers (5-zazcytidine，nicotinamide, suberoylanilide hydroxamic acid) were applied to induce the metabolites of Penicillium mallochii CCH01, a fungus isolated from the gut of Ectropis oblique. Metabolite profiles of P. mallochii CCH01 was obviously changed by suberoylanilide hydroxamic acid (SAHA) treatment. Four metabolites (1-4), including 2 new natural sclerotioramine derivatives, isochromophilone XIV (1), isochromophilone XV(2) and 2 known compounds, sclerotioramine (3) and (+)-sclerotiorin (4), were isolated and purified from P. mallochii CCH01 treated with SAHA. Their structures were determined by spectroscopic analyses. Anti-phytopathogenic activities of the isolated compounds 1-4 were investigated under laboratory conditions, and compound 4 showed broad and important inhibition activities against Curvularia lunata (IC50 = 2.1 μg/mL), C. clavata (IC50 = 21.0 μg/mL), Fusarium oxysporum f. sp. Mornordica (IC50 = 40.4 μg/mL) and Botryosphaeria dothidea (IC50 = 27.8 μg/mL), which were comparable to those of referenced cycloheximide, with IC50 values of 0.3, 5.0, 12.4 and 15.3 μg/mL, respectively. Ingredients 2 and 3 showed selective and potent activities against Colletotrichum graminicola with the IC50 values of 29.9 and 9.7 μg/mL, respectively. Furthermore, the antibacterial bioassays showed that compounds 3 and 4 exhibited strong inhibition activities against Bacillus subtilis, with disc diameters of zone of inhibition (ZOI) of 9.1mm and 9.1mm respectively, which were a bit weaker than that of referenced gentamycin with ZOI of 10.8 mm. Additionally, the new metabolite 1 showed a promising activity against Canidia albicans (ZOI =10.5 mm), comparable to that of positive amphotericin B with ZOI of 23.2 mm. The present results suggest that chemical epigenetic modifier induction was a promising approach to obtaining antimicrobial metabolites encoded by silent biosynthetic of P. mallochii.