‘David and Goliath’ of the soil food web – Flagellates that kill nematodes

• Published in: Soil biology & biochemistry Vol. 40; no. 8; pp. 2032 - 2039
• Main Authors: Bjornlund, L, Ronn, R
• Format: Journal Article
• Language: English
• Published: Oxford Elsevier Ltd 01.08.2008; New York, NY Elsevier Science
• Subjects: Agronomy. Soil science and plant productions; Bacterial feeding; Biochemistry and biology; Biological and medical sciences; Caenorhabditis elegans; Cercomonas; Chemical, physicochemical, biochemical and biological properties; ecological competition; Flagellates; flagellum; Food web; food webs; Fundamental and applied biological sciences. Psychology; Microfauna; Nematoda; Nematodes; Physics, chemistry, biochemistry and biology of agricultural and forest soils; population density; Predation; Protozoa; soil bacteria; soil fauna; soil nematodes; Soil science; species diversity; Trophic interaction; trophic relationships; Caenorhabditis elegans; Protozoa; Microfauna; Food web; Bacterial feeding; Flagellates; Cercomonas; Nematodes; Trophic interaction; Predation; Fauna; Trophic relation; Bacterivorous; Trophic chain; Soils; Helmintha; Nemathelminthia; Soil science; Invertebrata; Nematoda
• ISSN: 0038-0717; 1879-3428
• DOI: 10.1016/j.soilbio.2008.04.011

Nematodes and flagellates are important bacterial predators in soil and sediments. Generally, these organisms are considered to be competitors for bacterial food. We studied the interaction among flagellates and nematodes using axenic liquid cultures amended with heat-killed bacteria as food and showed for the first time that a small and common soil flagellate ( Cercomonas sp.) is able to attack and kill the much larger nematode Caenorhabditis elegans. The killing process is not caused by soluble metabolites but requires direct contact between the flagellate cells and the nematode surface and occurs rapidly (within a few hours) at high flagellate density. At lower flagellate density, adult nematodes sometimes avoid attachment of flagellates, feed on them and become the dominant bacterial predator. Considering that bacterial feeders affect bacterial communities differently, and that one bacterial feeder can control the abundance of another, suggests a new perspective on how bacterial diversity and trophic interactions are linked in the soil food web.