Production of an isonitrile antibiotic by an UV-induced mutant of Trichoderma harzianum

Strain improvement of Trichoderma harzianum for enhanced biocontrol capacity: Strategies and prospects

In the control of plant diseases, biocontrol has the advantages of being efficient and safe for human health and the environment. The filamentous fungus Trichoderma harzianum and its closely related species can inhibit the growth of many phytopathogenic fungi, and have been developed as commercial biocontrol agents for decades. In this review, we summarize studies on T. harzianum species complex from the perspective of strain improvement. To elevate the biocontrol ability, the production of extracellular proteins and compounds with antimicrobial or plant immunity-eliciting activities need to be enhanced. In addition, resistance to various environmental stressors should be strengthened. Engineering the gene regulatory system has the potential to modulate a variety of biological processes related to biocontrol. With the rapidly developing technologies for fungal genetic engineering, T. harzianum strains with increased biocontrol activities are expected to be constructed to promote the sustainable development of agriculture.

Biocontrol potential of saline- or alkaline-tolerant Trichoderma asperellum mutants against three pathogenic fungi under saline or alkaline stress conditions

Salinity and alkalinity are major abiotic stresses that limit growth and development of poplar. We investigated biocontrol potential of saline- and alkaline-tolerant mutants of Trichoderma asperellum to mediate the effects of salinity or alkalinity stresses on Populus davidiana×P. alba var. pyramidalis (PdPap poplar) seedlings. A T-DNA insertion mutant library of T. asperellum was constructed using an Agrobacterium tumefaciens mediated transformation system; this process yielded sixty five positive transformants (T1-T65). The salinity tolerant mutant, T59, grew in Potato Dextrose Agar (PDA) containing up to 10% (1709.40mM) NaCl. Under NaCl-rich conditions, T59 was most effective in inhibiting Alternaria alternata (52.00%). The alkalinity tolerant mutants, T3 and T5, grew in PDA containing up to 0.4% (47.62mM) NaHCO₃. The ability of the T3 and T5 mutants to inhibit Fusarium oxysporum declined as NaHCO₃ concentrations increased. NaHCO₃ tolerance of the PdPap seedlings improved following treatment with the spores of the WT, T3, and T5 strains. The salinity tolerant mutant (T59) and two alkalinity tolerant mutants (T3 and T5) generated in this study can be applied to decrease the incidence of pathogenic fungi infection under saline or alkaline stress.

Isolation of the antibiotic methyl (R,E)-3-(1-hydroxy-4-oxocyclopent-2-en-1-yl)-acrylate EA-2801 from Trichoderma atroviridae

The endophytic Trichoderma atroviridae UB-LMA was isolated as a symbiont of Taxus baccata and analyzed for its antimicrobial activity. By applying an original approach consisting of solid-state cultivation coupled with solid-phase extraction, a new methyl (R,E)-3-(1-hydroxy-4-oxocyclopent-2-en-1-yl)-acrylate derivative named EA-2801 (1) was isolated together with the previously reported isonitrin A and dermadin methyl ester. The chemical structure of 1 was determined by NMR and MS. Compound 1 showed antimicrobial activity against a panel of Gram-positive and -negative bacteria.

Unraveling the efficient applications of secondary metabolites of various Trichoderma spp

Recent shift in trends of agricultural practices from application of synthetic fertilizers and pesticides to organic farming has brought into focus the use of microorganisms that carryout analogous function. Trichoderma spp. is one of the most popular genera of fungi commercially available as a plant growth promoting fungus (PGPF) and biological control agent. Exploitation of the diverse nature of secondary metabolites produced by different species of Trichoderma augments their extensive utility in agriculture and related industries. As a result, Trichoderma has achieved significant success as a powerful biocontrol agent at global level. The endorsement of Trichoderma spp. by scientific community is based on the understanding of its mechanisms of action against a large set of fungal, bacterial and in certain cases viral infections. However, it is still an agnostic view that there could be any single major mode of operation, although it is argued that all mechanisms operate simultaneously in a synchronized fashion. The central idea behind this review article is to emphasize the potentiality of applications of target specific secondary metabolites of Trichoderma for controlling phytopathogens as a substitute of commercially available whole organism formulations. With the aim to this point, we have compiled an inclusive list of secondary metabolites produced by different species of Trichoderma and their applications in diverse areas with the major emphasis on agriculture. Outlining the importance and diverse activities of secondary metabolites of Trichoderma besides its relevance to agriculture would generate greater understanding of their other important and beneficial applications apart from target specific biopesticides.

Purification and determination of the chemical structure of the tyrosinase inhibitor produced by Trichoderma viride strain H1-7 from a marine environment

Tyrosinase is a key enzyme in the synthesis of melanin and is widely distributed in animals, plants, and microorganisms. As excessive melanin production causes not only hyperpigmenting effects on human skin but also melanosis in various foods, an inhibitor of tyrosinase has become of interest lately from a practical point of view. In the present study, we purified the tyrosinase inhibitor produced by Trichoderma viride strain H1-7 from a marine environment. The purified inhibitor showed a single peak on HPLC. The chemical structure of this compound was determined by NMR and mass spectrometry analyses. The structure was the same as homothallin II that has been isolated as an antibiotic from T. koningii and T. harzianum. The inhibitor showed competitive inhibition against mushroom tyrosinase.

The current and future applications of microorganism in the bioremediation of cyanide contamination

Inorganic cyanide and nitrile compounds are distributed widely in the environment, chiefly as a result of anthropogenic activity but also through cyanide synthesis by a range of organisms including higher plants, fungi and bacteria. The major source of cyanide in soil and water is through the discharge of effluents containing a variety of inorganic cyanide and nitriles. Here the fate of cyanide compounds in soil and water is reviewed, identifying those factors that affect their persistence and which determine whether they are amenable to biological degradation. The exploitation of cyanides by a variety of taxa, as a mechanism to avoid predation or to inhibit competitors has led to the evolution in many organisms of enzymes that catalyse degradation of a range of cyanide compounds. Microorganisms expressing pathways involved in cyanide degradation are briefly reviewed and the current applications of bacteria and fungi in the biodegradation of cyanide contamination in the field are discussed. Finally, recent advances that offer an insight into the potential of microbial systems for the bioremediation of cyanide compounds under a range of environmental conditions are identified, and the future potential of these technologies for the treatment of cyanide pollution is discussed.

Mycotoxin production by indoor molds

Fungal growth in buildings starts at a water activity (a(w)) near 0.8, but significant quantities of mycotoxins are not produced unless a(w) reaches 0.95. Stachybotrys generates particularly high quantities of many chemically distinct metabolites in water-damaged buildings. These metabolites are carried by spores, and can be detected in air samples at high spore concentrations. Very little attention has been paid to major metabolites of Stachybotrys called spirocyclic drimanes, and the precise structures of the most abundant of these compounds are unknown. Species of Aspergillus and Penicillium prevalent in the indoor environment produce relatively low concentrations of mycotoxins, with the exception of sterigmatocystins that can represent up to 1% of the biomass of A. versicolor at a(w)'s close to 1. The worst-case scenario for homeowners is produced by consecutive episodes of water damage that promote fungal growth and mycotoxin synthesis, followed by drier conditions that facilitate the liberation of spores and hyphal fragments.

Colour pigments of Trichoderma harzianum. Preliminary investigations with thin-layer chromatography-Fourier transform infrared spectroscopy and high-performance liquid chromatography with diode array and mass spectrometric detection

The colour pigments of Trichoderma harzianum fermentation broth were separated and the main fractions were tentatively identified by reversed-phase thin-layer chromatography-Fourier transform infrared spectroscopy (RP-TLC-FT-IR), RP-HPLC-diode array detection and RP-HPLC-MS. It was established that the multistep gradient elution developed for RP-TLC separation of pigments can be successfully used as a pilot method for the rational design of gradient elution in RP-HPLC for the separation of the same pigments. FT-IR and MS measurements were unable to identify the exact chemical structures of the main pigment fractions, the presence of OH, =CH and C=O (RP-TLC-FT-IR) and OH and NH, substructures (RP-HPLC-MS) was confirmed. It was assumed that the main pigment fractions are oxidation polymers originating from monomer molecules containing polar substructures and double bonds in the alkyl chain which are liable for oxidation during the aerobic fermentation process.

Physiological and biochemical characterization of Trichoderma harzianum, a biological control agent against soilborne fungal plant pathogens

Monoconidial cultures of 15 isolates of Trichoderma harzianum were characterized on the basis of 82 morphological, physiological, and biochemical features and 99 isoenzyme bands from seven enzyme systems. The results were subjected to numerical analysis which revealed four distinct groups. Representative sequences of the internal transcribed spacer 1 (ITS 1)-ITS 2 region in the ribosomal DNA gene cluster were compared between groups confirming this distribution. The utility of the groupings generated from the morphological, physiological, and biochemical data was assessed by including an additional environmental isolate in the electrophoretic analysis. The in vitro antibiotic activity of the T. harzianum isolates was assayed against 10 isolates of five different soilborne fungal plant pathogens: Aphanomyces cochlioides, Rhizoctonia solani, Phoma betae, Acremonium cucurbitacearum, and Fusarium oxysporum f. sp. radicis lycopersici. Similarities between levels and specificities of biological activity and the numerical characterization groupings are both discussed in relation to antagonist-specific populations in known and potential biocontrol species.