Abstract. – Background and Objective: To evaluate the mosquito larvicidal potential of the native Bacillus thuringiensis isolate BtReX02, which was isolated from a tropical rain forest ecosystem in Malaysia. This study also aimed at determining the phenotypic and bio- chemical characteristics of the isolate. Materials and methods: The phenotypic char- acterization was carried out by growing the iso- late in nutrient broth to observe the colonial morphology, vegetative cells, sporulation, motili- ty and haemolytic activity. The parasporal crys- tal morphology was determined by Coomassie Brilliant Blue (CBB) staining of the sporulated cells and then observed under light microscope. The mosquito larvicidal assay was conducted with the second instar larvae of Culex quinque- fasciatus and Aedes albopictus to determine the entomocidal potency of the isolate. The total protein profile was determined by SDS-PAGE. Results and Discussion: Preliminary pheno- typic and biochemical characterization showed that the isolate is motile, an indirect indication of the virulence of the strain and exhibited he- molytic activity, an important feature of an- tidipteran Bacillus thuringiensis strains. Study on the crystal morphology showed the presence of cuboidal crystals, another characteristic fea- ture of a mosquitocidal Bacillus thuringiensis strains. Bioassay with the second instar larvae of Culex quinquefasciatus, Aedes albopictus es- tablished the antidipteran activity of this native Bacillus thuringiensis isolate. Protein profile analysis revealed the unique pattern showing high molecular mass as well as low molecular mass proteins corresponding to the Cry and Cyt proteins respectively. The protein profile is strik- ingly different from other mosquitocidal strains European Review for Medical and Pharmacological Sciences Mosquitocidal activity of a native Bacillus thuringiensis isolate Bt ReX02 from Gunung Jerai Forest, Malaysia against Culex quinquefasciatus and Aedes albopictus A. PRAZANNA LAKXMY, R. XAVIER, C.M. REENA JOSEPHINE, Y.W. LEE*, K. MARIMUTHU, S. KATHIRESAN, S. SREERAMANAN** Department of Biotechnology, Faculty of Applied Sciences, Aimst University, Semeling, Kedah Darul Aman (Malaysia) *Coopers Lifesci Sdn-Bhd-WellTech Health care Group, Kuala Lumpur (Malaysia) **School of Biological sciences, Universiti Sains Malaysia (USM), Penang (Malaysia) Corresponding Author: Rathinam Xavier, Ph.D; e-mail: rxavier77@yahoo.com 149 such as Bacillus thuringiensis subsp.israelensis and Bacillus thuringiensis subsp. jegathesan Periodical introduction of such native strains of Bacillus thuringiensis will add a new weapon in the armoury to manage the vector borne dis- eases and also in the management of insect re- sistance. Key Words: Bacillus thuringiensis, Larvicidal activity, Culex quin- quefasciantus, Aedes albopictus. Introduction Mosquitovectorscontinuetobeaseriouspub- lic health problem world over. The most impor- tant among are the genus Anopheles, Culex and Aedes, whichareresponsiblefortransmittingthe pathogens of malaria, filariasis, dengue and chikungunya.Mosquitocontrolbyapplicationof synthetic insecticides posed many serious prob- lems including rapid development of insecticide resistance among the mosquitoes. Currently, an integratedvectorcontrolstrategyhasbeenadvo- cated with major focus on utilization of biocon- trolagentssuchas Bacillus thuringiensis (Bt) Bt is a Gram-positive soil bacterium characterized byitsabilitytoproduceproteinaciouscrystalline inclusions during sporulation. These crystalline inclusionsalsoknownasinsecticidalcrystalpro- 2011; 15: 149-155