Halophilic microorganisms are already in use for some biotechnological processes, such as commercial production of ß-carotene, polymers (polyhydroxyalkanoates and polysaccharides), enzymes, compatible solutes etc. Considering their commercial importance, food samples (crude salt crystals and raw mango pickle) were used for isolation of halotolerant microorganisms. Two bacterial isolates obtained from food samples were examined for their ability to survive under stressed conditions and their growth response in increasing levels of NaCl (1 to 15% w/v), pH (5.0 to 10.0) and temperature (10 to 70°C). The isolates were rod shaped Gram-positive, salt-tolerant, non-halophilic, nitrogen-fixing strains. Different sugars such as glucose, fructose, maltose, sucrose, xylose and lactose were used to check for acid and gas production. The organisms were studied for their ability to hydrolyse substrates such as casein, starch, gelatin, etc. These organisms (i) grew well in SM basal salt medium and nitrogen-free semi-solid LGI medium (ii) tolerated 10-15% salt concentration (iii) produced acid from D-glucose, D-fructose and sucrose and (iv) utilized glycerol and citrate as carbon source, and v) survived acidic (pH 4-5) and alkaline (pH 9-10) conditions. The results suggested that there is potential to improve their performance as sources of industrially important enzymes. On the basis of morphological attributes and biochemical characteristics the isolates belonged to the genus Bacillus. The results of partial sequencing of 16S rRNA also revealed that the isolates 1 and 2 are closely related to Bacillus subtilis subsp. subtilis NCIB 3610T (97.9% pairwise similarity) and Bacillus sonorensis NRRL B-23154T (99.8% pair-wise similarity) respectively. ACKNOWLEDGMENTSFig 3. Growth curves of isolates I and II. The cells were inoculated in the broth, incubated at 37°C, 120 rpm and their growth was determined by measuring the absorbance at 660 nm.a) In nutrient broth, b) In nutrient broth containing 10% and 15% NaCl, respectively. Arahal DR, Carmen Marquez M, Volcani BE, Schleifer KH, Ventosa A (1999) Bacillup. nov. a new moderately halophilic species from the Dead Sea. International Journal of Systematic Bacteriology 49, 521-530. Asha Devi NK, Balakrishnan K, Gopal R, Padmavathy S (2008) Bacillus clausii MB9 from the east coast regions of India: Isolation, biochemical characterization and antimicrobial activity. Current Science 95, 627-636. Ausubel FM, Rrent R, Kingston RE, Moore DD, Seidman JG, Smith JA, Struhl K (1987) Current Protocaol in Molecular Biology. Wiley, New York. Bordeleau LM, Prevost D (1994) Nodulation and nitrogen fixation in extreme environments. Plant and Soil 161, 115-125. Cavalcante VA, Dobereiner J (1988) A new acid-tolerant nitrogen fixing bacterium associated with sugar cane. Plant Soil 108, 23-31.
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