Räuberische Pilze mit Anwendungspotenzial

Nematode-trapping fungi, such as Duddingtonia flagrans, are fascinating carnivorous microorganisms. In a nutrient-rich environment they live as saprotrophs, but if nutrients are scarce and in the presence of nematodes, they can switch to a predatory lifestyle. The switch is characterized by the formation of complex, adhesive trap structures. The interaction requires a sophisticated interspecies communication with pheromones, secondary metabolites, and virulence factors.

Pathogenicity and Volatile Nematicidal Metabolites from Duddingtonia flagrans against Meloidogyne incognita

Plant parasitic nematodes, especially parasitic root-knot nematodes, are one of the most destructive plant pathogens worldwide. The control of plant root-knot nematodes is extremely challenging. Duddingtonia flagrans is a type of nematode-trapping fungi (NTF), which produces three-dimensional adhesive networks to trap nematodes. In this study, the pathogenicity and volatile organic compounds (VOCs) of the NTF D. flagrans against the plant root-knot nematode, Meloidogyne incognita, were investigated. The predatory process of D. flagrans trapping M. incognita was observed using scanning electron microscopy. Gas chromatography-mass spectrometry analysis of the VOCs from D. flagrans led to the identification of 52 metabolites, of which 11 main compounds were tested individually for their activity against M. incognita. Three compounds, cyclohexanamine, cyclohexanone, and cyclohexanol, were toxic to M. incognita. Furthermore, these three VOCs inhibited egg hatching of M. incognita. Cyclohexanamine showed the highest nematicidal activity, which can cause 97.93% mortality of M. incognita at 8.71 µM within 12 h. The number of hatched juveniles per egg mass after 3 days was just 8.44 when treated with 26.14 µM cyclohexanamine. This study is the first to demonstrate the nematicidal activity of VOCs produced by D. flagrans against M. incognita, which indicates that D. flagrans has the potential to biocontrol plant root-knot nematodes.

The STRIPAK component SipC is involved in morphology and cell-fate determination in the nematode-trapping fungus Duddingtonia flagrans

The striatin-interacting phosphatase and kinase complex (STRIPAK) is a highly conserved eukaryotic signaling hub involved in the regulation of many cellular processes. In filamentous fungi, STRIPAK controls multicellular development, hyphal fusion, septation and pathogenicity. In this study we analyzed the role of the STRIPAK complex in the nematode-trapping fungus Duddingtonia flagrans which forms three-dimensional, adhesive trapping networks to capture Caenorhabditis elegans. Trap networks consist of several hyphal loops which are morphologically and functionally different from vegetative hyphae. We show that lack of the STRIPAK component SipC (STRIP1/2/HAM-2/PRO22) results in incomplete loop formation and column-like trap structures with elongated compartments. The misshapen or incomplete traps lost their trap identity and continued growth as vegetative hyphae. The same effect was observed in the presence of the actin cytoskeleton drug cytochalasin A. These results could suggest a link between actin and STRIPAK complex functions.

Fatal attraction of Caenorhabditis elegans to predatory fungi through 6-methyl-salicylic acid

Salicylic acid is a phenolic phytohormone which controls plant growth and development. A methyl ester (MSA) derivative thereof is volatile and involved in plant-insect or plant-plant communication. Here we show that the nematode-trapping fungus Duddingtonia flagrans uses a methyl-salicylic acid isomer, 6-MSA as morphogen for spatiotemporal control of trap formation and as chemoattractant to lure Caenorhabditis elegans into fungal colonies. 6-MSA is the product of a polyketide synthase and an intermediate in the biosynthesis of arthrosporols. The polyketide synthase (ArtA), produces 6-MSA in hyphal tips, and is uncoupled from other enzymes required for the conversion of 6-MSA to arthrosporols, which are produced in older hyphae. 6-MSA and arthrosporols both block trap formation. The presence of nematodes inhibits 6-MSA and arthrosporol biosyntheses and thereby enables trap formation. 6-MSA and arthrosporols are thus morphogens with some functions similar to quorum-sensing molecules. We show that 6-MSA is important in interkingdom communication between fungi and nematodes.

Recent Advances in the Control of Helminths of Domestic Animals by Helminthophagous Fungi

This review describes the advances acquired and proven in the use of helminthophagous fungi in the control of gastrointestinal helminth parasites in domestic animals. Old and well-known premises about parasitic epidemiology and the factors that can interfere with the best performance of biological control are mentioned. Some of the most promising fungi are Duddingtonia flagrans from the predatory fungi group and Pochonia chamydosporia and Mucor circinelloides from the ovicidal fungi group. These fungi produce resistance spores called chlamidospores. Bioverm® and BioWorma®, based on the fungus D. flagrans, are available as commercial. Biotechnological products such as nanoparticles and obtaining primary and secondary metabolites have already been obtained from these fungi. Because they have different mechanisms of action, ovicidal and predatory fungi, when used together, can present a complementary and synergistic action in the biological control of helminths. Therefore, future research in the search for new formulations, the association of fungi from different groups, extraction of new molecules, and nanoparticles of these fungi in the control of helminths in various domestic animals are desired.

Biological control of nematodes by nematode-trapping fungi Duddingtonia flagrans in naturally infected sheep in southern Brazil

The aim of this study was to evaluate the anti-helminthic effect of a commercial formulation Bioverm® (Duddingtonia flagrans) in 28 sheep naturally infected with gastrointestinal nematodes. Animals were classified into two groups: G1 (n=14) treated with nematophagous fungi and G2 (n=14) untreated control. The efficacy of the anti-helminthic drug was assessed based on the egg count per gram of feces (EPG) of strongyles, larval culture, hemogram, leukogram, plasma protein levels, mucosal coloration using the FAMACHA© method, animals body weight, and evaluating the ocular mucosa for the FAMACHA© anemia guide were performed at days 0, 30, 60, 90, 120, 150, and 180. Additionally, the nematode larvae were quantified in the dry matter of the pastures of both groups. Results showed that the EPG was significantly decreased in animals receiving nematophagous fungi from D30 until the experiment end. The most common nematode genus was Haemonchus (63%), followed by Cooperia (23%) and Trichostrongylus (15%). Based on the fecal egg count reduction test (FECRT), treated animals showed a reduction of fecal egg count of 58.9%, 8.6, 92.8%, 96.4%, and 96.2%, at D30, D60, D90, D120, and D180, respectively. The absolute values of red blood cells and leukocytes were significantly increased at D60 and D90, respectively, in the treated animals. A significant weight gain was observed in the treated ewes at the end of the experiment; however, there was no correlation between the EPGs values and hematocrit with the FAMACHA© degrees of animals in both experimental groups. The mean EPG of both groups and the number of infectious larvae in the pastures were not directly proportional. In conclusion, nematophagous fungi contributed to decreased parasitic load in sheep, and consequently, improve animal performance; they can be a suitable alternative to reduce problems associated with nematode infections.