Disentangling nematode-bacteria interactions using a modular soil model system and biochemical markers

Abstract

Interactions between bacteria and nematode grazers are an important component of soil food webs yet, due to the cryptic habitat, they are almost exclusively investigated in artificial agar substrate. Transport, food choice and foraging experiments were performed in a modular microcosm system with the nematode Acrobeloides buetschlii and bacterial diets (Escherichia coli, Pseudomonas putida and Bacillus subtilis) in gamma-irradiated soil. Bacterial biomass was assessed by soil phospholipid fatty acids (PLFAs). Continuous random foraging of nematodes was affected by soil type. Food choice experiments revealed diet switch and time lag preference responses, suggesting that nematode population fluctuations are driven by multiple factors such as bacterial attractants, defence strategies or food quality. Application of PLFA markers revealed a strong nematode predation pressure, as biomass in P. putida declined by 50%, whereas no transport of bacteria through soil was indicated. Overall, semi-natural experimental systems are an essential prerequisite to gain a realistic picture in microbial-microfaunal interactions.

A Review of Prospective Biocontrol Agents and Sustainable Soil Practices for Bulb Mite (Acari: Acaridae) Management

“…Service crops regulate soil moisture and temperature, enhance organic matter and soil structure, paving the way for the rehabilitation of beneficial microbiota and mesofauna (including mites and nematodes) in agricultural soils [95,[97][98][99]. Free living nematodes (FLN) are known to move to bacterial and fungi hotspots [100], attracted by volatiles released from the microbiota community developing on organic matter. FLN use the microbiota as a food source, but apart from this, FLN may disperse bacteria and fungi [101].…”