Date of Graduation

1994

Document Type

Dissertation/Thesis

Abstract

The following investigation examined a biological system employing bacterially-derived 2-ketogluconate (2KG) for the dissolution of insoluble soil phosphates. It has been suggested that 2KG solubilizes insoluble soil phosphates by either a reduction in soil pH or by chelating divalent cations. The capability of 2KG derived from Pseudomonas aeruginosa PAO1 to solubilize phosphate ores and the mechanism by which this dissolution occurs were investigated in vitro and in vivo. The dissolution of all three ores was shown to be dose-dependent, non-linear, and not correlated with a significant reduction in pH of the solution. The dissolution of IP and RP resulted in a recurrent rise and fall in the concentration of inorganic phosphate (Pi) released into solution. These results support a mechanism for the dissolution of insoluble phosphates by 2KG in which it forms a weak cation-sugar chelation complex that releases Pi into solution, but as the complex dissociates, the Pi is re-complexed with the cation causing the precipitous drop in Pi concentration observed. To investigate the ability of 2KG to produce phosphorus from insoluble ores in a form available to plants, a greenhouse experiment utilizing silica sand as the soil medium and tomato as the model organism was undertaken. The results showed that phosphorus deficiency symptoms were alleviated in plants treated with 350 {dollar}\\mu{dollar}g/ml of 2KG plus RP or AP, but wet weight, dry weight, growth and phosphate uptake were not significantly different from those treated with water plus RP or AP. 2KG did not have a significant effect on IP in vivo. The gene encoding D-gluconate dehydrogenase (Gln DH), the enzyme responsible for 2KG production, was a candidate for transfer into the roots of commercial agricultural crops. In an attempt to clone Gln DH, a monoclonal antibody of class IgM was produced, but the antibody was not useful for DNA library screening. Gln DH was then subjected to chemical and enzymatic digestion for amino acid sequencing, but proved to be refractory to all digestions suggesting that the N-termini are blocked and that the enzyme undergoes post-translational modifications such as glycosylation.

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