ABSTRACT
The bacterial isolate Bacillus thuringiensis TS110 was isolated from the rice field soil of Burdwan district, West Bengal, India. Bioassay test of the bacteria TS110 against 3rd, 4th and 5th instar larvae of Cnaphalocrocis medinalis was carried out. Cut leaf assay, potted plant assay and field assay were done. During filed assay, it has been observed that the LC50 (×107) values of TS110 against 3rd, 4th and 5th instar larvae of C. medinalis were 3.77, 5.29, 4.83 and 4.93, 4.42, 4.72 in dry and wet season, respectively. The morphological, biochemical and phylogenetic analysis of the isolate TS110 were done. TS110 was positive for catalase, nitrate reductase, methyl red, voges-proskauer, oxidase, urease, indole, citrate utilization, arginine dihydrolase test, starch, lipid, gelatin, casein, and lecithin hydrolysis test. TS110 showed fermentation test positive for glucose, fructose, mannose, arabinose and trehalose in nutrient broth medium. The antibiotic sensitivity test showed that the bacterial isolate was sensitive to kanamycin (30 µg/disc), nalidixic acid (30 µg/disc), rifampicin (5 µg/disc), doxycycline (30 µg/disc), gatifloxacin (10 µg/disc), vancomycin (30 µg/disc), gentamycin (10 µg/disc), ampicillin (10 µg/disc), ofloxacin (5 µg/disc), levofloxacin (5 µg/disc), streptomycin (10 µg/disc), gentamycin (10 µg/disc). The phylogenetic analysis revealed that TS110 was closely related to different species of B. thuringiensis submitted to the GenBank. On the basis of morpho-physiological and molecular characterization, the bacterial isolate was identified as B. thuringiensis.
ABSTRACT
A new Gram-positive, nonpigmented, rod-shaped fluoride-tolerant bacterial strain, NM25, was isolated from waterlogged muddy field soil collected from the fluoride endemic area of Rampurhat II block (average fluoride in water, 4.7 mg/l, and in soil, 1.5 mg/kg) in Birbhum District, West Bengal, India. The study was undertaken to characterize the fluoride-tolerant bacterial isolate, to determine its role in bioaccumulation of fluoride, and to analyze the water and soil quality of the bacterial environment. The isolate was positive for catalase, lipase, urease, protease, oxidase, and H2S production, but negative for indole production, nitrate reduction, and Vogues-Proskauer test. The organisms were sensitive to recommended doses of ofloxacin, kanamycin, rifampicin, levofloxacin, vancomycin, gatifloxacin, gentamicin, doxycycline, streptomycin, and nalidixic acid but resistant to ampicillin. Based on the phenotypic characteristics, 16S rRNA gene sequence, and phylogenetic analysis, the bacterial isolate NM25 was identified as Bacillus flexus. The G+C content of the 16S rDNA was 53.14 mol%. This strain tolerated up to 20% (w/v) NaCl in nutrient agar medium and was grown at the pH range 4-12. It reduced fluoride concentration up to 67.45% and tolerated more than 1,500 ppm of fluoride in brain-heart infusion agar medium.
