Nutrition on bacteria by bacterial-feeding nematodes and consequences on the structure of soil bacterial community

Bacterial-feeding nematodes are, with protozoa, the main grazers of soil bacteria. Interactions between bacteria and nematodes have important repercussions on soil functioning and particularly on nutrient availability. We assessed the influence of the bacterial strains ingested on bacterial-feeding nematodes population development and also the consequences of nematode feeding behaviour on the structure of the soil microbial community with a special attention to different soil micro-habitats for nematode and bacteria. In vivo studies conducted in the presence of single bacterial strains showed that the type of ingested bacteria conditioned the development of the different bacterial-feeding Cephalobidae nematode species tested and that the effect of bacteria differed between nematode species. The spatial distribution of soil nematodes between three soil habitats (fresh organic matter, inter-aggregates pores and aggregates) depended of the trophic behaviour of nematodes. Bacterial-feeding nematodes and fungal-feeding nematodes showed comparable distribution: being preferentially located in the fresh organic matter and in the inter-aggregate pores. Besides, the activity of inoculated bacterial-feeding nematodes modified the genetic structure of the soil microbial community. Bacterial community of the macroporosity was significantly influenced by the nematodes. On the contrary, no modification of the structure of the bacterial community linked with nematode activity was measured in the bulk soil.