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M. Sc. Dissertations

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Subject: Microbiology × Author: Aastha × End date: 2016 × Type: Thesis × Thesis Type: M.Sc ×
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    ThesisItemOpen Access
    Isolation and characterization of sulphur oxidizing bacteria
    (CCSHAU, 2014) Aastha; Goyal, Sneh
    Sulphur is considered as the fourth major plant nutrient after N, P and K and is one of the sixteen nutrient elements, which are essential for the growth and development of plants especially in the agricultural crop production. Sulphur undergoes a number of biological transformations in nature carried out exclusively by microorganisms. The transformations of inorganic sulphur compounds in nature have been formalized in the sulphur cycle. Sulphur oxidation is the most important step of sulphur cycle which improves soil fertility. It results in the formation of sulphate, which can be used by the plants while the acidity produced by oxidation helps to solubilize plant nutrients and improves soil. Microorganisms that are capable of oxidizing reduced inorganic sulphur compounds with sulphate as the end product are known as sulphur oxidizing bacteria (SOB) . A total of 65 bacterial isolates were isolated from rhizospheric soils of mustard crops and decomposing sites. Out of 65 bacterial isolates, 55 isolates were screened on the basis of bromo cresol purple dye reduction test. Among 55 isolates, 32 bacterial isolates were further screened for their ability to produce sulphate by barium chloride test. The two isolates SOB98 and SOBD42 showed maximum sulphate production 2.631 and 2.331mM respectively. These isolates were selected for optimization of the cultural conditions for the sulphate production. Glucose was found to be the best carbon source and ammonium chloride was the best nitrogen source. It was observed that 30ÂșC was the optimum temperature for sulphate production by isolate(s) SOB98 and SOBD42. Sulphate production by isolate SOB98 and SOBD42 was maximum after 7 days of incubation and at pH 6 and pH4, respectively. Sulphide oxidase activity of isolates SOB98 and SOBD42 were 32.3 and 26.9 U/ml, respectively. On the basis of morphological and biochemical tests the promising isolates probably belonged to genera Xanthobacter sp. (SOB98) and Pseudomonass sp. (SOBD42).