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dc.contributor.advisorGardner, Wayne Stanley, 1941-en
dc.contributor.advisorPease, Tamara Kayeen
dc.creatorSouza, Afonso Cesar Rezende de, 1968-en
dc.date.accessioned2011-03-22T20:50:42Zen
dc.date.available2011-03-22T20:50:42Zen
dc.date.issued2009-08en
dc.identifier.urihttp://hdl.handle.net/2152/10625en
dc.descriptiontexten
dc.description.abstractThe respective kinetics of bacterial leucine aminopeptidase and [beta]-glucosidase activities were investigated to improve understanding of factors controlling activity and hydrolytic capacity in estuarine organic-poor sands. Depth distributions of enzyme activity and bulk organic matter content were determined in sediments of Aransas Bay and Copano Bay Texas, to investigate enzyme dynamics as related to the geochemical properties of the sediment. Vertical profiles of activity in sediment showed that the enzymes were more active at the surface and that the potential hydrolysis rate of leucine aminopeptidase was higher than that of [beta]-glucosidase. Vertical patterns of enzyme activity correlated (weakly) with variations in sediment organic matter (TOC, TN, and carbohydrates) content. Enrichments of sediment samples with monomeric organic compounds and inorganic nutrients did not affect leucine aminopeptidase and [beta]-glucosidase activities in short- and long-term incubations. Enzyme activity was independent of nutrient availability and suggested that microbial communities were not nutrient-limited. Time-course assays of bacterial hydrolysis of TOC, TN, and carbohydrates provided information about how substrate limitation may affect enzyme activity. Positive correlations between bulk TOC and TN content and enzyme activity indicated enzyme dependence on polymeric substrate content. Induction of enzyme activity after sediment enrichments with specific labile compounds confirmed the importance of available organic substrate to enzyme hydrolysis efficiency. A kinetic approach established the occurrence of enzyme inhibition and its effects on enzyme hydrolytic capacity. The addition of a specific-enzyme substrate to sediment samples modified enzyme parameters and indicated that a substrate-reversible type of inhibitor could reduce enzyme hydrolytic capacity. The addition of polyphenol, as a natural inhibitor of enzyme activity, to the sediment resulted in a concomitant reduction of leucine aminopeptidase activity and ammonium regeneration rate, and thus demonstrated a close coupling between enzyme activity and sediment ammonium regeneration. These research results demonstrate the dynamic nature of the hydrolytic enzymes, provide information about the mechanisms of induction and inhibition of activity, and demonstrate some implications of reducing the hydrolytic capacity to organic matter decomposition and nutrient regeneration rates.en
dc.format.mediumelectronicen
dc.language.isoengen
dc.rightsCopyright is held by the author. Presentation of this material on the Libraries' web site by University Libraries, The University of Texas at Austin was made possible under a limited license grant from the author who has retained all copyrights in the works.en
dc.subjectMicrobial extracellular enzymesen
dc.subjectEnzyme kineticsen
dc.subjectEnzyme activityen
dc.subjectEnzyme dynamicsen
dc.subjectOrganic-poor sandsen
dc.subjectEstuarine sandsen
dc.subjectAransas Bay, Texasen
dc.subjectCopano Bay, Texasen
dc.subjectBacterial leucine aminopeptidaseen
dc.subject[beta]-glucosidaseen
dc.subjectSedimentsen
dc.subjectHydrolysisen
dc.subjectEnzyme hydrolytic capacityen
dc.subjectSouth Texasen
dc.titleActivity and kinetics of microbial extracellular enzymes in organic-poor sands of a south Texas estuaryen
dc.description.departmentMarine Scienceen
thesis.degree.departmentMarine Science Instituteen
thesis.degree.disciplineMarine Scienceen
thesis.degree.grantorThe University of Texas at Austinen
thesis.degree.levelDoctoralen
thesis.degree.nameDoctor of Philosophyen


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