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Molecular Characterization of Bacillus thuringiensis Strains Isolated from a Selected Site in Nochchiyagama, Anuradhapura in Sri Lanka

Authors:

MCM Zakeel ,

Faculty of Agriculture, Rajarata University of Sri Lanka, Puliyankulama, Anuradhapura, LK
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DMD Dissanayake,

Faculty of Agriculture, Rajarata University of Sri Lanka, Puliyankulama, Anuradhapura, LK
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PA Weerasinghe

Faculty of Agriculture, Rajarata University of Sri Lanka, Puliyankulama, Anuradhapura, LK
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Abstract

The protein toxins produced by Bacillus thuringiensis are the most widely used natural insecticides in vector and pest control in agriculture. B. thuringiensis strains present in surface and sub-surface soil samples collected from Nochchiyagama were isolated by 0.25M sodium acetate selection method. Isolated B. thuringiensis was grown on Luria Bertani agar medium and stained by Gram staining procedures. Sixty isolates of B. thuringiensis were identified by Coomassie Blue staining procedure and characterized based on colony morphology, crystal shape, plasmid profile and bioassay. Results revealed that sub-surface samples had more B. thuringiensis counts than surface soils. This study also indicated that B. thuringiensis was abundant in soils contaminated with animal wastes. All the isolates formed ‘pan cake' shape circular colonies with smooth or serrate margins with varying diameter. Fifty five isolates were found to have rod shape crystals, 4 were spherical shape and only one isolate had rhomboidal shape crystal. Thirty six isolates were toxic to the third instar larvae of Aedes aegypti including the isolate which contained rhomboidal shape crystal. All the other isolates found toxic to the mosquito larvae consisted with rod shape crystal inclusion bodies. There were eight different B. thuringiensis strains among the isolates and 55% of these were B. thuringiensis israelensis.

Key words: Bacillus thuringiensis; Colony shape; Molecular characterization; Parasporal crystal inclusion; Plasmid

DOI: 10.4038/tare.v12i1.1981

Tropical Agricultural Research & Extension 12(1):2009 31-34

DOI: http://doi.org/10.4038/tare.v12i1.1981
How to Cite: Zakeel, M., Dissanayake, D. & Weerasinghe, P., (2010). Molecular Characterization of Bacillus thuringiensis Strains Isolated from a Selected Site in Nochchiyagama, Anuradhapura in Sri Lanka. Tropical Agricultural Research and Extension. 12(1), pp.31–34. DOI: http://doi.org/10.4038/tare.v12i1.1981
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Published on 11 Jun 2010.
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