Degradation of phenolic and chloroaromatic compounds by Coprinus spp

White rot fungal impact on the evolution of simple phenols during decay of silver fir wood by UHPLC-HQOMS

INTRODUCTION

Silver fir (Abies alba Mill.) is one of the most valuable conifer wood species in Europe. Among the main opportunistic pathogens that cause root and butt rot on silver fir are Armillaria ostoyae and Heterobasidion abietinum. Due to the different enzymatic pools of these wood-decay fungi, different strategies in metabolizing the phenols were available.

OBJECTIVE

This work explores the changes in phenolic compounds during silver fir wood degradation.

METHODOLOGY

Phenols were analyzed before and after fungus inoculation in silver fir macerated wood after 2, 4 and 6 months. All samples were analyzed using high-performance liquid chromatography coupled to a hybrid quadrupole-orbitrap mass spectrometer.

RESULTS

Thirteen compounds, including simple phenols, alkylphenyl alcohols, hydroxybenzoketones, hydroxycinnamaldehydes, hydroxybenzaldehydes, hydroxyphenylacetic acids, hydroxycinnamic acids, hydroxybenzoic acids and hydroxycoumarins, were detected. Pyrocatechol, coniferyl alcohol, acetovanillone, vanillin, benzoic acid, 4-hydroxybenzoic acid and vanillic acid contents decreased during the degradation process. Methyl vanillate, ferulic acid and p-coumaric were initially produced and then degraded. Scopoletin was accumulated. Pyrocatechol, acetovanillone and methyl vanillate were found for the first time in both degrading and non-degrading wood of silver fir.

CONCLUSIONS

Despite differences in the enzymatic pool, both fungi caused a significant decrease in the amounts of phenolic compounds with the accumulation of the only scopoletin. Principal component analysis revealed an initial differentiation between the degradation activity of the two fungal species during degradation, but similar phenolic contents at the end of wood degradation.

Cucumber (Cucumis sativus L.) Seedling Rhizosphere Trichoderma and Fusarium spp. Communities Altered by Vanillic Acid

Root exudates mediate soil microbiome composition and diversity, which might further influence plant development and health. Vanillic acid from root exudates is usually referred as autotoxin of cucumber, however, how vanillic acid affect soil microbial community diversities and abundances remains unclear. In this study, vanillic acid (VA; 0.02, 0.05, 0.1, and 0.2 μmol g^-1 soil) was applied to soil every other day for a total of five applications. We used Illumina MiSeq sequencing, quantitative PCR (qPCR) and PCR-denaturing gradient gel electrophoresis (PCR-DGGE) to test the effects of VA on the total fungi community composition as well as the Trichoderma and Fusarium spp. community abundances and structures in the cucumber rhizosphere. Illumina MiSeq sequencing showed that VA (0.05 μmol g^-1 soil) increased the relative abundance of the fungal phylum Basidiomycota while decreasing the relative abundance of Ascomycota (P < 0.05), and not altered the diversity of the soil fungal community. VA (0.05 μmol g^-1 soil) also increased the relative abundances of the fungal genera with plant pathogens, such as Conocybe and Spizellomyces spp.(P < 0.05). A qPCR analysis showed that VA (0.05 to 0.2 μmol g^-1 soil) exerted promoting effects on Trichoderma spp. community abundance and stimulated Fusarium spp. abundance at low concentrations (0.02 to 0.05 μmol g^-1 soil) but inhibited it at high concentrations (0.1 to 0.2 μmol g^-1 soil). The PCR-DGGE analysis showed that all concentrations of VA altered the community structures of Trichoderma spp. and that the application of VA (0.02 and 0.05 μmol g^-1 soil) changed the band number and the Shannon-Wiener index of the Fusarium spp. community. This study demonstrated that VA changed the total fungal community in the cucumber seedling rhizosphere and that the Trichoderma and Fusarium spp. communities showed different responses to VA.

Diversification of fungal specific class a glutathione transferases in saprotrophic fungi

Glutathione transferases (GSTs) form a superfamily of multifunctional proteins with essential roles in cellular detoxification processes and endogenous metabolism. The distribution of fungal-specific class A GSTs was investigated in saprotrophic fungi revealing a recent diversification within this class. Biochemical characterization of eight GSTFuA isoforms from Phanerochaete chrysosporium and Coprinus cinereus demonstrated functional diversity in saprotrophic fungi. The three-dimensional structures of three P. chrysosporium isoforms feature structural differences explaining the functional diversity of these enzymes. Competition experiments between fluorescent probes, and various molecules, showed that these GSTs function as ligandins with various small aromatic compounds, derived from lignin degradation or not, at a L-site overlapping the glutathione binding pocket. By combining genomic data with structural and biochemical determinations, we propose that this class of GST has evolved in response to environmental constraints induced by wood chemistry.

Trichoderma harzianum SQR-T037 rapidly degrades allelochemicals in rhizospheres of continuously cropped cucumbers

To alleviate the stress of continuous cropping for cucumber continuous cropping (CCC) system, a beneficial fungus Trichoderma harzianum SQR-T037 (SQR-T037) was isolated and applied to soil to degrade allelochemicals exuded from cucumber plants in a Rhizobox experiment. The following phenolic acids (PAs), classified as allelochemicals, were isolated and identified from cucumber rhizospheres: 4-hydroxybenzoic acid, vanillic acid, ferulic acid, benzoic acid, 3-phenylpropionic acid, and cinnamic acid. Mixed PAs added in potato dextrose broth, each with 0.2 gram per liter, were completely degraded by SQR-T037 after 170 h of incubation. In Rhizobox experiments, inoculation of SQR-T037 in the CCC soil also degraded the PAs exuded from cucumber plant roots. This degradation was 88.8% for 4-hydroxybenzoic acid, 90% for vanillic acid, 95% for benzoic acid, and 100% for ferulic acid, 3-phenylpropionic acid, and cinnamic acid at 45 days after plantation. Simultaneously, a significant (p ≥ 0.05) decrease in the disease index of Fusarium wilt and an increase in dry weights of cucumber plants were obtained in pot experiments by application of SQR-T037. This was mostly attributed to degradation of PAs exuded from cucumber roots in CCC soil by SQR-T037 and alleviation of the allelopathic stress. Application of beneficial microorganisms, such as SQR-T037 that biodegrades allelochemicals, is a highly efficient way to resolve the problems associated with continuous cropping system.

Biodegradation of anthracene and fluoranthene by fungi isolated from an experimental constructed wetland for wastewater treatment

Pilot-scale constructed wetlands were used to treat water contaminated by polycyclic aromatic hydrocarbons (PAHs), particularly fluoranthene, and the possible role of fungi present in these ecosystems was investigated. A total of 40 fungal species (24 genera) were isolated and identified from samples (gravel and sediments) from a contaminated wetland and a control wetland. All of them were assayed for their ability to remove anthracene (AC) and fluoranthene (FA) from liquid medium. FA was degraded efficiently by 33 species while only 2 species were able to remove AC over 70%. A selection of 10 strains of micromycetes belonging to various taxonomic groups was further investigated for FA and AC degradation, toxicity assays and phenoloxidases (POx) detection. Interesting and not previously reported species were revealed (Absidia cylindrospora, Cladosporium sphaerospermum, and Ulocladium chartarum). They were all able to highly degrade the PAH-model compounds chosen. An interesting inducibility was noted for Ulocladium chartarum. Degradative ability of fungi was not related to their extracellular POx activity. This study may contribute to the improvement of constructed wetlands for water treatment, which may be enriched in efficient fungi.

Removal of herbicides from liquid media by fungi isolated from a contaminated soil

Fungi were isolated from soil samples corresponding to pesticide-contaminated soil (CS) and noncontaminated soil (NCS) in the Annaba vicinity (Algeria) and identified. The number of isolates obtained from CS and NCS were 263 and 288, respectively. The most frequent species (Aspergillus fumigatus, A. niger, A. terreus, Absidia corymbifera, and Rhizopus microsporus var microsporus) were not sensitive to the pesticides. The growth of the genus Trichoderma was inhibited by the pesticides, while genera Absidia and Fusarium were stimulated. The 53 species isolated were assayed for their ability to remove metribuzin from liquid medium. Only Botrytis cinerea from NCS and Sordaria superba and Absidia fusca from CS removed more than 50% of the compound after 5 d. Metamitron was very resistant. Among the 21 species tested, only Alternaria solani (from NCS), Drechslera australiensis (from CS and NCS), and Absidia fusca (from CS) reduced the concentration in the medium more than 10% (10-16%). Twelve species were grown with linuron, seven of them were inefficient in removing this compound. The two strains of Sordaria macrospora yielded 22 to 25% depletion, while Botrytis cinerea depleted linuron almost completely. Among the 31 species assayed for their ability to eliminate metobromuron, Botrytis cinerea (from CS and NCS) depleted almost completely the chemical from the medium. Rhizopus oryzae and Absidia fusca from CS removed 40 and 47% of the compound, respectively. No systematic relationships were observed between the soil contamination and herbicide elimination capacities of soil fungi. Absidia fusca and Botrytis cinerea were particularly interesting for bioremediation purposes because they were able to transform efficiently three of the four compounds assayed.

Production, characterization and properties of polysaccharide depolymerizing enzymes from a strain of Curvularia inaequalis

Xylanase, beta-glucosidase, beta-xylosidase, endoglucanase and polygalacturonase production from Curvularia inaequalis was carried out by means of solid-state and submerged fermentation using different carbon sources. beta-Glucosidase, beta-xylosidase, polygalacturonase and xylanase produced by the microorganisms were characterized. beta-Glucosidase presented optimum activity at pH 5.5 whereas xylanase, polygalacturonase and beta-xylosidase activities were optimal at pH 5.0. Maximal activity of beta-glucosidase was determined at 60 degrees C, beta-xylosidase at 70 degrees C, and polygalacturonase and xylanase at 55 degrees C. These enzymes were stable at acidic to neutral pH and at 40-45 degrees C. The crude enzyme solution was studied for the hydrolysis of agricultural residues.