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dc.contributor.advisorPolacco, Joseph C., 1944-eng
dc.contributor.authorWitzig, Stephen B.eng
dc.date.issued2007eng
dc.date.submitted2007 Summereng
dc.descriptionThe entire dissertation/thesis text is included in the research.pdf file; the official abstract appears in the short.pdf file (which also appears in the research.pdf); a non-technical general description, or public abstract, appears in the public.pdf file.eng
dc.descriptionTitle from title screen of research.pdf file (viewed on May 12, 2009)eng
dc.descriptionIncludes bibliographical references.eng
dc.descriptionThesis (M.S.) University of Missouri-Columbia 2007.eng
dc.descriptionDissertations, Academic -- University of Missouri--Columbia -- Biochemistry (Agriculture)eng
dc.description.abstractPink-Pigmented Facultative Methylotrophic bacteria (PPFMs, Methylobacterium spp.) have been found to be the most abundant microorganisms among phylloplane microflora, and have been recovered from all plants examined. I examined the ability of resident PPFMs to mimic the urease-negative phenotype of two mutant classes of urease-negative soybean hosts. The working model is that there is a signal from the plant that either inhibits the production of the urease gene products in the associated bacteria or inhibits the function or transport of Ni²⁺ from the plant to the bacteria. My studies led to the overall conclusion that urease is essential for assimilation of urea and of ureides, that urease has a constitutive basal level of expression and is "induced" by the ureide allantoin and "repressed" by the preferential nitrogen source, ammonium. However, these nitrogenous signals are not responsible for the urease-negative status of the plant associated PPFMs. Our working model has shifted to a block in Ni²⁺ uptake necessitating examination of Ni²⁺ content in these bacteria. I attempted the recolonization of plants with PPFMs to determine how this affects urease activity in recovered isolates. In the course of these studies it became obvious that the interactions between PPFMs and the host plant is an intimate one because seed-reintroduced strains, though colonizing the host plant, were not seed-transmitted. In addition, PPFM interactions with Arabidopsis and with soybean were distinguishable, in that only in the latter were endogenous PPFMs urease-negative on mutant hosts defective in urease accessory genes.eng
dc.identifier.merlinb67532317eng
dc.identifier.oclc320843828eng
dc.identifier.urihttps://hdl.handle.net/10355/5049
dc.identifier.urihttps://doi.org/10.32469/10355/5049eng
dc.languageEnglisheng
dc.publisherUniversity of Missouri--Columbiaeng
dc.relation.ispartofcollectionUniversity of Missouri--Columbia. Graduate School. Theses and Dissertationseng
dc.source.originalSubmitted by University of Missouri--Columbia Graduate School.eng
dc.subject.lcshMethylotrophic bacteriaeng
dc.subject.lcshMethylobacteriumeng
dc.subject.lcshUreaseeng
dc.subject.lcshHost plantseng
dc.titleSignals affecting the urease status of plant-associated bacteria, Methylobacterium sppeng
dc.typeThesiseng
thesis.degree.disciplineBiochemistry (Agriculture) (MU)eng
thesis.degree.grantorUniversity of Missouri--Columbiaeng
thesis.degree.levelMasterseng
thesis.degree.nameM.S.eng


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