Edible mushrooms of the genus Pleurotus as biocontrol agents of parasites of importance for livestock

Background: Edible mushrooms have nutraceutical properties, mainly in humans, animals and plants. Pleurotus species represent an alternative approach to parasite control because they have nematocidal activity against different taxonomic genera of nematodes of importance for livestock (e.g., eggs and infective and histotrophic larvae of Haemonchus contortus), as well as against other parasites of importance in animal health. Objective: To present a general overview of fungi of the genus Pleurotus and their characteristics as a sustainable method of biocontrol for parasitic nematodes of animals with importance in public health. Methods: This bibliographic review was carried out by consulting published studies on edible fungi of the genus Pleurotus and analyzing their properties related to nematocidal activity. The works were grouped according to their research focus; works related to keywords and topics in livestock were identified in indexed journals and on digital platforms. Results and conclusions: Pleurotus spp. produce different secondary metabolites with antiparasitic activities, mainly anthelmintic and particularly against gastrointestinal nematodes and their larval stages. The characteristics of these fungi are excellent for biotechnological applications since they produce a wide range of secondary metabolites in different parts, such as in the basidiomas, mycelia and degraded substrates.

Isolation and Characterization of Strain Exiguobacterium sp. KRL4, a Producer of Bioactive Secondary Metabolites from a Tibetan Glacier

Extremophilic microorganisms represent a unique source of novel natural products. Among them, cold adapted bacteria and particularly alpine microorganisms are still underexplored. Here, we describe the isolation and characterization of a novel Gram-positive, aerobic rod-shaped alpine bacterium (KRL4), isolated from sediments from the Karuola glacier in Tibet, China. Complete phenotypic analysis was performed revealing the great adaptability of the strain to a wide range of temperatures (5–40 °C), pHs (5.5–8.5), and salinities (0–15% w/v NaCl). Genome sequencing identified KRL4 as a member of the placeholder genus Exiguobacterium_A and annotation revealed that only half of the protein-encoding genes (1522 of 3079) could be assigned a putative function. An analysis of the secondary metabolite clusters revealed the presence of two uncharacterized phytoene synthase containing pathways and a novel siderophore pathway. Biological assays confirmed that the strain produces molecules with antioxidant and siderophore activities. Furthermore, intracellular extracts showed nematocidal activity towards C. elegans, suggesting that strain KRL4 is a source of anthelmintic compounds.

Lon protease- and temperature-dependent activity of a lysis cassette located in the insecticidal island of Yersinia enterocolitica

The Yersinia genus comprises pathogens that are able to adapt to an environmental life cycle stage as well as to mammals. Yersinia enterocolitica strain W22703 exhibits both insecticidal and nematocidal activity conferred by the tripartite toxin complex (Tc) that is encoded on the 19 kb pathogenicity island Tc-PAIYe. All tc genes follow a strict temperature regulation in that they are silenced at 37°C, but activated at lower temperatures. Four highly-conserved phage-related genes, located within the Tc-PAIYe, were recently demonstrated to encode a biologically functional holin-endolysin gene cassette that lyses its own host W22703 at 37°C (1). Conditions transcriptionally activating the cassette are yet unknown. In contrast to E. coli, the overproduction of holin and endolysin did not result in cell lysis of strain W22703 15°C. When the holin-endolysin genes were overexpressed at 15°C in four Y. enterocolitica biovars and in four other Yersinia spp., a heterogenous pattern of phenotypes was observed, ranging from lysis resistance of a biovar 1A strain to a complete growth arrest of a Y. kristensenii strain. To decipher the molecular mechanism underlying this temperature-dependent lysis, we constructed a Lon protease negative mutant of W22703 in which overexpression of the lysis cassette leads to cell death at 15°C. Overexpressed endolysin exhibited a high proteolytic susceptibility in strain W22703, but remained stable in strain W22703 Δlon or in Y. pseudotuberculosis. Although artificial overexpression was applied here, the data indicate that Lon protease plays a role in the control of the temperature-dependent lysis in Y. enterocolitica W22703. IMPORTANCE The investigation of the mechanisms that help pathogens to survive in the environment is a prerequisite to understand their evolution and their virulence capacities. In members of the genus Yersinia, many factors involved in virulence, metabolism, motility or biofilm formation follow a strict temperature-dependent regulation. While the molecular mechanisms underlying activation of determinants at body temperature have been analysed in detail, the molecular basis of low temperature-dependent phenotypes is largely unknown. Here, we demonstrate that a novel phage-related lysis cassette, which is part of the insecticidal and nematocidal pathogenicity island of Y. enterocolitica, does not lyse its own host following overexpression at 15°C, and that the Lon protease is involved in this phenotype.

Design, synthesis, and biological activity of novel 1,2,4-oxadiazole derivatives

Background Plant diseases seriously threaten food security, it is urgent to discover efficient and low-risk chemical pesticides. 1,2,4-Oxadiazole derivatives exhibit broad spectrum of agricultural biological activities. For discovering novel molecules with excellent agricultural activities, novel 1,2,4-oxadiazole derivatives were synthesized and evaluated for their agricultural activities. Result Bioassays results showed that the title compounds exhibited moderate nematocidal activity against Meloidogyne incognita and anti-fungal activity to Rhizoctonia solani. It’s worth noting that compounds 5m, 5r, 5u, 5v, 5x and 5y showed strong antibacterial effects on Xanthomonas oryzae pv. oryzae (Xoo), with EC50 values of 36.25, 24.14, 28.82, 19.44, 25.37 and 28.52 μg/mL, respectively, superior to bismerthiazol (BMT, EC50 = 77.46 μg/mL) and thiodiazole copper (TDC, EC50 = 99.31 μg/mL). Compounds 5p, 5u and 5v exhibited excellent antibacterial ability against Xanthomonas oryzae pv. oryzicola (Xoc), with EC50 values of 31.40, 19.04 and 21.78 μg/mL, respectively, better than that of BMT (EC50 = 68.50 μg/mL) and TDC (EC50 = 91.05 μg/mL). In addition, compound 5v exerted moderate antibacterial effects on rice bacterial leaf blight. Conclusions Twenty-six novel 1,2,4-oxadiazole derivatives were obtained and their biological activities were evaluated. Compound 5u and 5v exhibited excellent antibacterial activity Xoo and Xoc. These results indicated that 1,2,4-oxadiazole derivatives containing a trifluoromethyl pyridine moiety could be as potential alternative templates for discovering novel antibacterial agents.

Nematocidal Activity on Onchocerca ochengi, Toxicity and Phytochemical Screening of Vernonia perrottetii Sch. Bip. Ex Walp (Asteraceae) Extracts

Onchocerciasis is a disease caused by a parasitic nematode Onchocerca volvulus in human. Ivermectin who is the main drug recommended for the treatment of this disease is only effective against the microfilarial stage of the parasite. Reports of emergence of parasite resistance to ivermectin have complicated onchocerciasis treatment and require to discover novel drugs. The objective of the present study was to investigate in vitro anthelmintic properties against the cattle filarial parasite Onchocerca ochengi, a model closely related to Onchocerca volvulus; and evaluate the toxicity (in vivo) of local medicinal plant Vernonia perrottetii. This plant is used as alternative medicine in the treatment of human onchocerciasis in central and coastal regions of Cameroon. Fifteen crude extracts were prepared from various parts of V. perrottetii using three organic solvents (70% ethanol, methanol, methylene chloride) and distilled water. The nematocidal activity was evaluated on adult worms of O. ochengi, worm viability was assessed biochemically using the dimethylthiazol (MTT) formazan assay. Oral toxicity of the promising extract was investigated in mice. The ethanolic extracts of the leaves and roots of V. perrottetii recorded the highest activities against adult male worms (LC50 of 29.80 μg/mL for leaves and 39.36 μg/mL for root). By contrast, the methanol and aqueous extracts of leaves and roots, of the plant as well as the mixture methylene chloride/methanol extracts. For acute treatment, a single dose of 2000 mg/kg no induced critical behavioral changes or death. In sub- acute treatment, daily oral administration of hydro-ethanolic extracts of leaves at the dose of 250, 500 and 750 mg/kg revealed disturbances in the normal growth of animals as well as liver and kidney alterations. Phytochemical analysis of the active extracts revealed the presence of Polyphenols, tannins, saponins and flavonoids. This study revealed the anti-Onchocerca activities of V. perrottetii, indicating a possible new source for developing a phytomedicine or drug for the treatment of human onchocerciasis.