Christian Jensen

Bio: Christian Jensen is an academic researcher from Free University of Berlin. The author has contributed to research in topics: Soil test. The author has an hindex of 2, co-authored 2 publications receiving 25 citations.

Direct observation of trapping activities of nematode‐destroying fungi in the soil using fluorescence microscopy

Abstract: The nematophagous fungi (Arthrobotrys oligospora and Monacrosporium cionopagum) were observed under semi-natural conditions by fluorescence microscopy after fluochroming, using fluorescein-diacetate. The formation of 3-dimensional sticky networks and the capture of nematodes inside the soil could be demonstrated.

Dynamics of aggregate stability and biological binding agents during decomposition of organic materials

Abstract: The relative importance of different binding mechanisms and associated biological binding agents on aggregate stability is still unclear. The aim of this study was to evaluate the role of various aggregate binding agents during the decomposition of cauliflower residues, wheat straw, cattle manure and poultry woody compost. We measured aggregate stability, hot-water extractable polysaccharide, C mineralization, fungal and microbial biomass dynamics in an amended silt loam soil, under controlled conditions. Soil aggregate stability was measured using three methods involving fast wetting, slow wetting and mechanical breakdown. Aggregate stability to slow wetting followed the same dynamics as C mineralization and was well correlated with polysaccharide content for cauliflower residues and wheat straw. This relationship is in agreement with the hypothesis that the rapid microbially induced improvement in aggregate stability that follows fresh organic residue additions at least partly involves labile polysaccharides. The transient increase in the two other types of stability was not directly related to C mineralization dynamics and seemed to be influenced by fungal hyphal length. Fungi would provide resistance to mechanical breakdown and slaking. The dynamic behaviour of biological binding agents was only partly explained by the initial quality of the organic materials, as characterized by Van Soest proximal fractionation.

Arthrobotrys oligospora: a model organism for understanding the interaction between fungi and nematodes

Abstract: Arthrobotrys oligospora, a predacious fungus of nematodes, has been very useful in understanding the relationship between nematophagous fungi and their nematode hosts. Arthrobotrys oligospora is by far the most common nematode-trapping fungus with the characteristic ability of forming adhesive trapping nets once in contact with nematodes. This review highlights the versatility and development of A. oligospora as a system to identify and characterize the ecology and biology of nematode-trapping fungi. Using A. oligospora, advances in our knowledge of nematophagous fungi have been made through the discovery of special traits and virulence determinants involved in the pathogenic process, or by creating new ways of presenting these factors to the target nematodes. We argue for an increased role for A. oligospora in complementing other model systems in biological control research.

Investigation on the infection mechanism of the fungus Clonostachys rosea against nematodes using the green fluorescent protein

Abstract: The fungus Clonostachys rosea (syn. Gliocladium roseum) is a potential biocontrol agent. It can suppress the sporulation of the plant pathogenic fungus Botrytis cinerea and kill pathogenic nematodes, but the process of nematode pathogenesis is poorly understood. To help understand the underlying mechanism, we constructed recombinant strains containing a plasmid with both the enhanced green fluorescent protein gene egfp and the hygromycin resistance gene hph. Expression of the green fluorescent protein (GFP) was monitored using fluorescence microscopy. Our observations reveal that the pathogenesis started from the adherence of conidia to nematode cuticle for germination, followed by the penetration of germ tubes into the nematode body and subsequent death and degradation of the nematodes. These are the first findings on the infection process of the fungal pathogen marked with GFP, and the developed method can become an important tool for studying the molecular mechanisms of nematode infection by C. rosea.