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Title: Carbon Catabolite Repression of Organic Acids in Phosphate Solubilizing Klebsiella species
Researcher: Rajput MahendrapalSingh
Guide(s): Shalini Rajkumar
Keywords: Carbon
Phosphate Acids
University: Nirma University
Completed Date: 04/03/2016
Abstract: newlineCarbon catabolite repression (CCR) governs uptake and metabolism of preferred and newlinesecondary carbon sources. CCR may have effect on carbon source dependent plant growth newlinepromoting (PGP) properties like phosphate (P) solubilization. Glucose is by far the best newlinecarbon source known for organic acid production linked P solubilization. But catabolite newlinerepression may prevent the preferential utilization of glucose or the organic acid production. newlinePGP Bacteria with dual property of nitrogen (N2) fixation and P solubilization may solve dual newlinepurpose for plant providing it with fixed N2 and soluble P. We looked for the succinate newlinemediated catabolite repression of the organic acid production linked P solubilization. Two newlinestrains of free living N2 fixing Klebsiella (SM6 and SM11) were isolated from rhizospheric newlinesoil that solubilized mineral phosphate (Ca-P and Rock P) by secretion of organic acid from newlineglucose. HPLC analysis showed that oxalic acid was the major organic acid produced by both newlinethe strains when bacteria are grown in glucose. P solubilization was observed only when newlineglucose was the sole carbon source and was completely inhibited in presence of succinate newlinesingly or along with glucose. Enzymes activities of glucose dehydrogenase (GDH; newlineperiplasmic glucose oxidation), isocitrate lyase (ICL) and glyoxylate oxidase (GO) newlineresponsible for oxalic acid production were estimated. The enzymes GDH, ICL and GO were newlinerepressed in succinate grown cells. While significant activity of ICL, the key enzyme for newlinecarbon flux through glyoxylate shunt and oxalic acid production during growth on glucose newlinesuggested that it could be inducible in nature, and its inhibition by succinate appeared to be newlinesimilar to catabolite repression. Diauxic growth profile showed that succinate was not newlinepreferentially utilized over glucose. Expression studies carried out form glucose, succinate newlineand glucose+succinate grown cells of both isolates showed that iclR, repressor of glyoxalate newlineshunt, was expressed when growth media contained succinate and the repre
Appears in Departments:Institute of Science

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05_acknowledgement.pdf110.83 kBAdobe PDFView/Open
06_contents.pdf98.25 kBAdobe PDFView/Open
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08_list_of_figures.pdf74.81 kBAdobe PDFView/Open
09_abbreviations.pdf143.64 kBAdobe PDFView/Open
11_chapter2.pdf924.46 kBAdobe PDFView/Open
12_chapter3.pdf444.92 kBAdobe PDFView/Open
13_chapter4.pdf939.9 kBAdobe PDFView/Open
14_summary.pdf144.99 kBAdobe PDFView/Open
15_bibliography.pdf264.36 kBAdobe PDFView/Open
16_list_of_publications.pdf75.86 kBAdobe PDFView/Open
1_title.pdf12.07 kBAdobe PDFView/Open

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