J. Basic Microbiol. 40 (2000) 5 – 6, 385 – 388 (Department of Applied Biology, Jordan University of Science and Technology, Irbid-22110, Jordan) Diversity of Bacillus thuringiensis in different habitats of Northern Jordan MAHER OBEIDAT, FOUAD AL-MOMANI and ISMAIL SAADOUN (Received 31 May 2000/Accepted 22 August 2000) A survey of Bacillus thuringiensis was conducted for 17 locations in Northern Jordan representing 12 different habitats. Eighty isolates were identified as B. thuringiensis in the majority of the tested samples. Results showed that soils contaminated with the slaughterhouses waste materials had the highest content of spore-forming bacteria [(4.05–2.2) 10 7 CFU/g)] and B. thuringiensis [(4.05 – 7.9) 10 7 CFU/g)] with a (5.5% – 14.9%) and (5.2% – 7.7%) of the total viable bacterial count, respectively. These bacteria were more abundant in soils contaminated with such animal by-products. All over the world Bacillus thuringiensis isolates are screened to identify new strains with high levels of insecticidal activity. Novel isolates with insecticidal activity recovered from numerous sources particularly soil (DULMAGE and AIZAWA 1982, SMITH and COUCHE 1991, YAMAMOTO and POWELL 1993). Other sources as grain dusts, diseased insect larvae, animal feed mills, phyloplane and aquatic environments have been reported (COOLE 1995). This bacterium is widely distributed and recovered from 70% of soil samples being stu- died from all continents (KARAMANLIDOU et al. 1991) with Asian samples were the most rich in B. thuringiensis. B. thuringiensis subsp. israelensis, and B. thuringiensis subsp. Kurstaki were the most common types (MARTIN and TRAVERS 1989). The purpose of this work is to study the abundance, distribution and diversity of B. thu- ringiensis isolates in different habitats of Northern Jordan. Materials and methods Sample collection: A total of 40 samples were collected from 12 different habitats in Northern Jordan including: 5 samples of olive-solid byproducts, 5 samples of grain dusts, 1 sample of bee-wax, 4 samples of liquid industrial-byproducts, and 25 soil samples (4 samples of olive-cultivated soils, 4 samples of animal manure-contaminated soils, 2 samples of decomposed animal bodies con- taminated soils, 3 samples of soils of oil-change-car stations, 4 samples of slaughter houses- contaminated soils, 2 samples of soils of waste collection pond edges, 4 samples of soils contaminated with waste water treatment plants, and 2 samples of dam sediments) (Table 1). Isolation of bacteria: Isolation of Bacillus thuringiensis and other spore-former bacteria was done according to the method previously described by OHBA and AIZAWA (1986) followed by TRAVERS method (TRAVERS et al. 1987). One gram or ml of each sample was suspended in sterile distilled water and heated at 80 °C for 30 min. Heat-treated or pasteurized suspension was diluted and plated on nutrient agar then incubated at 30 °C for 24 h. Selection of Bacillus thuringiensis isolates was done by addition of pasteurized suspension to 10 ml of LB broth buffered with 0.25 M sodium acetate pH 6.8. The suspensions were incubated at 30 °C for 4 h then heated to 80 °C for 3 min. Suspensions were diluted and plated on T3 medium (Travers and Reichelderfer 1987). Cells were examined under light microscope to observe the parasporal bodies.