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Experimental and modelling studies on the fate in soil of introduced biologically-contained bacteria


The objectives are the development and testing of safe carrier organisms for the application of beneficial genes to soil.
A biological system is being developed for the efficient control of bacterial populations released into soil for biocontrol purposes. The system is based on genes naturally present in bacteria.

Initial objectives include the insertion and further development of inducible killing genes into soil isolates, microcosm testing on nonbiologically contained (parent) bacteria, development of detection methodology from soil, selection of crucial parameters for a model, and studies on responses of bacteria to nutrient and other stresses.

The end objective of the project is the biocontrol of dipteran insects which damage gramineous plants. Research is thus focused on the insertion of the 3'-truncated fragment of the delta endotoxin gene from Bacillus thuringiensis var morrisoni (cryIVB) in soil bacteria adapted to the rhizosphere of graminea. For this purpose two Pseudomonas strains P fluorescens R2f and P cepacia P2, were isolated P fluorescens R2f was first selected as a carrier for cryIVB, sinceit is most amenable to genetic modification.

Research is proceeding as planned.
The broad objective of this project is to provide a way for the safe introduction of genetically-engineered microorganisms (GEMs) into soil. The project is linked to an Agricultural Research Organization Wageningen project aimed at developing biological alternatives (based on Bacillus thuringiensis crystal protein genes) for the control of insect larvae feeding on grass and cereal roots. To improve the biosafety of such releases, an intrinsic control system based on host-killing genes will be inserted into soil bacteria and the behaviour of these in soil situations will be tested.
Special focus will be on the development of a regulatory system of the suicide system which, even though killing off introduced bacterial cells, will permit survival of the bulk of the introduced population in soil for an adequate period of time (controlled survival). Suitable marker genes will also be inserted into the soil bacteria for the purpose of ecological testing. if time and regulatory constraints permit, the target bacteria, ie strains carrying the aforementioned Bacillus thuringiensis crystal protein genes, will be used. As a corollary, mathematical models predictive of such behaviour will be developed and validated against data obtained from soil microcosm and, if possible, field experiments.


Dienst Landbouwkundig Onderzoek
9750 RA Haren

Participants (3)

Business Unit of TNO Built Environment and Geosciences
Van Mourik Broekmanweg 6
2628 XE Delft
Danmarks Tekniske Universitet

2800 Lyngby
University of Goteborg
9 C,medicinaregatan
413 90 Göteborg