Mohammad Javad Rahimi

The neutral metallopeptidase NMP1 of Trichoderma guizhouense is required for mycotrophy and self‐defence

Trichoderma guizhouense NJAU 4742 (Harzianum clade) can suppress the causative agent of banana wild disease Fusarium oxysporum f. sp. cubense 4 (Foc4). To identify genes involved in this trait, we used T-DNA insertional mutagenesis and isolated one mutant that was unable to overgrow Foc4 and had reduced antifungal ability. Using the high-efficiency thermal asymmetric interlaced-PCR, the T-DNA was located in the terminator of a neutral metalloprotease gene (encoding a MEROPS family M35 protease), which was named nmp1. The antifungal activity of the mutant was recovered by retransformation with wild-type nmp1 gene. The purified NMP1 (overexpressed in Pichia pastoris) did not inhibit the growth and germination of other fungi in vitro. Its addition, however, partly recovered the antifungal activity of the mutant strain against some fungi. The expression of nmp1 is induced by the presence of fungi and by dead fungal biomass, but the time-course of transcript accumulation following the physical contact depends on mode of interaction: it increases in cases of long-lasting parasitism and decreases if the prey fungus is dead shortly after or even before the contact (predation). We thus conclude that NMP1 protein of T. guizhouense has major importance for mycotrophic interactions and defence against other fungi.

Massive lateral transfer of genes encoding plant cell wall-degrading enzymes to the mycoparasitic fungus Trichoderma from its plant-associated hosts.

Unlike most other fungi, molds of the genus Trichoderma (Hypocreales, Ascomycota) are aggressive parasites of other fungi and efficient decomposers of plant biomass. Although nutritional shifts are common among hypocrealean fungi, there are no examples of such broad substrate versatility as that observed in Trichoderma. A phylogenomic analysis of 23 hypocrealean fungi (including nine Trichoderma spp. and the related Escovopsis weberi) revealed that the genus Trichoderma has evolved from an ancestor with limited cellulolytic capability that fed on either fungi or arthropods. The evolutionary analysis of Trichoderma genes encoding plant cell wall-degrading carbohydrate-active enzymes and auxiliary proteins (pcwdCAZome, 122 gene families) based on a gene tree / species tree reconciliation demonstrated that the formation of the genus was accompanied by an unprecedented extent of lateral gene transfer (LGT). Nearly one-half of the genes in Trichoderma pcwdCAZome (41%) were obtained via LGT from plant-associated filamentous fungi belonging to different classes of Ascomycota, while no LGT was observed from other potential donors. In addition to the ability to feed on unrelated fungi (such as Basidiomycota), we also showed that Trichoderma is capable of endoparasitism on a broad range of Ascomycota, including extant LGT donors. This phenomenon was not observed in E. weberi and rarely in other mycoparasitic hypocrealean fungi. Thus, our study suggests that LGT is linked to the ability of Trichoderma to parasitize taxonomically related fungi (up to adelphoparasitism in strict sense). This may have allowed primarily mycotrophic Trichoderma fungi to evolve into decomposers of plant biomass.

Chemical Composition and Antimicrobial Activities of Three Satureja Species Against Food-borne Pathogens

Abstract Foods provide a natural and perfect medium for bacteria and fungi to multiply and growth. Awareness of people of synthetic additives and preservatives in food processing has led food industries to search for natural additives with a broad spectrum of antimicrobial activities. The chemical compositions of the essential oils (EOs) distilled from three Satureja spp. have been analyzed by gas chromatography-mass spectrometry (GC-MS). The antimicrobial activities of the EOs against microorganisms causing food-borne infections were determined by the broth micro-dilution method as recommended by the Clinical and Laboratory Standards Institute (CLSI). Analysis of the EOs showed that phenolic compound including thymol and carvacrol are the main components of the EOs. Inhibition studies indicated that the tested EOs entirely inhibited the growth of tested fungi at concentrations of less than 0.062 μl/mL. Moreover, the oils exhibited significant bacteriostatic and bactericidal activities against Gram-positive and Gram-negative bacteria at concentrations ranging from 0.031–1 μL/mL. Considering the wide range of antimicrobial activities of the examined EOs, they might have potential to be used in food industry as a natural preservative agent and to extend the shelf life of products.