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Survival growth and dispersal of indigenous and engineered bacteria mediatedby soil invertebrates


The aim is to assess the survival and dispersal of indigenous and genetically engineerd microorganisms in soils.

Fresh faeces of many soil invertebrates often contain higher counts of viable bacteria per gram than uningested soil and litter. Selective enrichment of some components of the soil bacteria community has also been reported. These effects are generally considered to be a consequence of bacteriolysis in the gut, growth of ingested and/or indigenous bacteria in the gut, growth in faecal material, changes in the physico chemical environment of microbial habitats, or a combination of these factors. The gust and faeces of invertebrates are therefore important sites of microbial activity.

Plasmid transfer has been reported in a variety of bacterial habitats ranging from mamalian and avian guts, sewage beds, the aquatic epilithon and the rhizosphere. Recent evidence also suggests that conditions in the guts of invertebrates may similarly encourage such genetic transfer so that a genetically engineered sequence could pass from its host strain into the indigenous bacteria and increase survival time in the soil. Alternatively the introduced bacteria may be ingested and dispersed by soil invertebrates away from the test side. Invertebrate activities may also reduce the viability of genetically engineered microorganisms(GEM) by feeding selectively in inoculation sites such as the rhizosphere.

The project will determine the dominant bacteria in the gut microflora of soil invertebrates (earthworms and arthropods) and how these may be perturbed by the presence of novel bacteria or GEMs introduced to the invertebrates by dietary manipulation. The survival and dispersal of the introduced bacteria will be assessed in contained experimental systems using techniques developed at ITAL. The responses of bacteria to low nutrient conditions in soils will be monitored to investigate how GEMs and introduced bacteria respond to starvation, particularly if starved dormant cells are formed, and whether these can be resuscitated in the nutrient rich conditions in guts and faeces. Finally, planted soil systems will allow the elucidation of the survival of GEMs within plant root systems, the bulk soil and the invertebrate population. Tests will include the use of soil bacteria encoded for the tox gene of Bacillus thuringiensis for the biological control of beatle larvae in pasture soils.


University of Exeter
Prince Of Wales Road
EX4 4PS Exeter
United Kingdom

Participants (1)

Stichting Instituut Voor de Toepassingvan Atoomenergie in de Landbouw
6700 AA Wageningen