Thesis (Ph. D.)--University of Wisconsin--Madison, 1982. / Typescript. Vita. Description based on print version record. Includes bibliographical references (leaves 127-136).

No description available.

Thesis (Ph. D.)--Leipzig. / Includes bibliographical references and index.

The genus Pantoea contains seven validly-published species, which are primarily known as plant-associated or phytopathogenic bacteria, but some have also been linked with human infections. Over the past six years, there have been increasing isolations of Pantoea strains from a range of hosts and locations which can not be conclusively identified. In South America and Uganda, Pantoea strains were isolated from Eucalyptus infected with bacterial blight. In South Africa, Pantoea strains were isolated from maize suffering from brown stalk rot and from onion seed. This has highlighted the need for a rapid, molecular-based technique to conclusively characterize these Pantoea strains. In the literature, two key taxonomic problems were identified within the genus Pantoea. The first involves three species isolated from fruit and soil samples in Japan, namely P. citrea, P. punctata and P. terrea, known as the “Japanese” Pantoea species. A recent review of the genus noted that Pantoea can be separated into two groups: the Pantoea “core” containing P. agglomerans, P. ananatis, P. dispersa and P. stewartii and the “Japanese” species. It was also stated that more taxonomic work is required to justify the assignment of the “Japanese” species to the genus Pantoea. The second taxonomic issue raised concerns over four DNA hybridization groups from a study of a large number of clinical strains belonging to the Erwinia herbicola-Enterobacter agglomerans complex. It had been previously suggested that these four DNA hybridization groups should belong to the genus Pantoea. The phylogenetic relationship between the Pantoea “core” species, the “Japanese” species and the four DNA hybridization groups is not clear. Multilocus sequence analysis (MLSA) was selected for a taxonomic study of the genus Pantoea The MLSA scheme was based on the sequences of four housekeeping genes: rpoB, atpD gyrB and infB. It was found that a phylogenetic tree of the concatenated sequences could differentiate all seven validly-published species as well as ten groups of strains from Eucalyptus, maize, onion, flowering shrubs and clinical isolates. The phylogenetic trees also confirmed the separation of Pantoea into two groups of species and indicated a close affiliation of the “Japanese” species with the genus Tatumella The clusters observed in the MLSA phylogenetic trees were confirmed by DNA-DNA hybridization. Using the MLSA data for support, four novel species were proposed from plant hosts: Pantoea vagens, Pantoea eucalypti, Pantoea deleyii and Pantoea anthophila. Four additional species were proposed for the clinical strains from the Erwinia herbicola-Enterobacter agglomerans complex, contained in three DNA hybridization groups: Pantoea septica, Pantoea eucrina, Pantoea brenneri and Pantoea conspicua. Phenotypic information and DNA-DNA hybridization values confirmed that the “Japanese” species were more similar to Tatumella than to Pantoea. This was demonstrated phylogenetically in the MLSA trees and gave support to transfer the “Japanese” species to the genus Tatumella. Additionally, a novel species was proposed for strains thought to belong to T.citrea, causing pink disease of pineapple: Tatumella morbirosei. Therefore, MLSA was not only proven to rapidly and successfully identify Pantoea strains, but also resolved the two major taxonomic issues within the genus. Please cite as follows: Brady, CL 2008, Taxonomic evaluation of the genus Pantoea based on a multigene approach, PhD thesis, University of Pretoria, Pretoria, viewed yymmdd < http://upetd.up.ac.za/thesis/available/etd-09182008-142751/ > Copyright / Thesis (PhD)--University of Pretoria, 2009. / Microbiology and Plant Pathology / unrestricted

Thesis (Ph. D.)--University of Wisconsin--Madison, 1955. / Typescript. Vita. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references (leaves 47-49).

Thesis (Ph. D.)--University of Florida, 1984. / Description based on print version record. Typescript. Vita. Includes bibliographical references (leaves 120-133).

No description available.

M.Sc. (Biochemistry) / Pseudomonas, as originally defined by Migula (1894), was a genus encompassing an assembly of rod-shaped, Gram-negative, aerobic gammaproteobacteria, possessing one or more polar flagella for motility. This vague description resulted in the misclassification of polarly flagellated proteobacteria that had not been completely characterized. Re-evaluation of the taxonomy of Pseudomonads was set into motion by advancements in molecular biology. Following this revision, Pseudomonads were clustered based on the homogeneity in their 16S rRNA sequence (Anzai et al., 2000). Research on Pseudomonas species has gained momentum owing to their significant prospects in biotechnological processes. Their exploitation for use as cleaning, biocontrol and bioremediation agents dates back to the 1980s (Sebastian and Kolattukudy, 1988; Weller, 1988)...

No description available.

Thesis (MSc)--University of Stellenbosch, 2000. / ENGLISH ABSTRACT: Agrobacterium tumefaciens-mediated transformation technology has been used in a variety of applications throughout the fields of cellular and molecular plant biology as well as plant physiology. Research is conducted in order to extend this application range and overcome some of the intrinsic limitations of the Agrobacterium transformation system. Predominantly, these limitations can be attributed to the host range specificity of A. tumefaciens, as well as adverse effects induced on explant tissue by active plant defence mechanisms, triggered by the plant-pathogen-interaction. Typically, this active defence mechanism culminates in the hypersensitive response (HR), characterised by localised cell death and necrosis. Not all Agrobacterium species, however, share the same host range and some have evolved the ability to infect plant species not normally considered hosts of A. tumefaciens. This host range specificity can be exploited to extend the application of existing Agrobacterium transformation systems. In an attempt to establish an efficient transformation system for Vitis vinifera which, has proven very difficult to transform with A. tumefaciens, indigenous A. vitis strains have been evaluated as possible host-specific transformation agents. Strains of Agrobacterium vitis should be suitable for this type of endeavour, since they have evolved several unique characteristics directly linked to the infection of their hosts. These include the ability to utilise, tartrate, a host abundant carbon source, as well as the production of an acid polygalacturonase that could play a role during the infection process. The proposition that the evolution of A. vitis is a fairly recent event is also confirmed by the relatively little divergence observed between A. tumefaciens and A. vitis. In this study, a selection of A. vitis strains were evaluated in screenings designed to accentuate desirable traits in strains such as good infectivity of grapevine material (presumably an indicator of an efficient mechanism of gene transfer to be exploited in an engineered transformation system) as well as a favourable reaction (causing no necrosis) on grapevine somatic embryos. Two strains produced large tumours on grapevine cuttings and caused little necrosis on the somatic embryos. Significant variation in infectivity as well as callus necrosis was observed between the strains as well as in a genotype-specific manner on the host material. This genotypic-specific effect of either host or pathogen could be an indication of the degree of specialisation developed by plant pathogens to infect specific hosts. On the basis of these results, it was possible to select an A. vitis strain for further biochemical and genetic characterisation. Simple biochemical analysis classified the strain as an octopine strain. DNA-DNA hybridisation techniques combined with a plasmid walking technique resulted in the partial characterisation of the T-DNA of the selected A. vitis strain. A partial restriction enzyme map of the T-DNA was constructed and the T-DNA and flanking areas were cloned. Significant differences, most notably, the absence of a TB-area as well as the absence of the agrocinopine (aes) gene from the 5' area of the T-DNA, were observed. Partial sequencing data indicated the presence of at least four conserved T-DNA genes located on the TA-DNA, as well as the presence of three bacterial insertion (IS-)elements flanking the region. Two of these IS elements, both related to the IS 110 family of IS elements have not yet been reported in A. vitis. In fact, these two elements seem to be the 5' and 3' ends of a disrupted element and could therefore have played an evolutionary role in the development of this strain. This study provides fundamental background for the development of a more efficient transformation system specific for grapevine, exploiting same of-the unique characteristics of one of its pathogens, A. vitis. / AFRIKAANSE OPSOMMING: Agrobacterium tumefaciens-gebaseerde transformasiesisteme word in "n wye reeks van toepassings in die velde van sellulêre- en molekulêre plantbiologie asook plantfisiologie aangewend. Navorsing word voortdurend onderneem om die inherente beperkinge van die Agrobacterium-transformasiesisteem te oorkom en sodoende die toepassingsveld van die sisteem verder te verbreed. Die beperkinge tipies aan dié sisteem kan hoofsaaklik toegeskryf word aan die gasheerspesifisteit van A. tumeteciens, asook die negatiewe reaksies op eksplantmateriaal wat deur die plant se aktiewe verdedigingsmeganisme, soos ontlok deur die plant-patogeen interaksie, veroorsaak word. Hierdie aktiewe verdedigingsmeganisme lei gewoonlik tot In hipersensitiewe respons (HR) in die plant, wat deur gelokaliseerde selafsterwing en nekrose gekenmerk word. Alle Agrobacterium-spesies het egter nie almal dieselfde gasheerreeks nie en sommige rasse het as gevolg van evolusionêre ontwikkelings die vermoë verkry om plantspesies wat normaalweg buite die gasheerreeks van A. tumefaciens val, te infekteer. Hierdie tipe gasheerspesifisiteit kan uitgebuit word om die toepassingsmoontlikhede van bestaande Agrobacterium-transformasiesisteme te verbreed. In In poging om In effektiewe transformasiesisteem vir Vitis vinifera, In moeilik transformeerbare gewas, te ontwikkel, is inheemse rasse van Agrobacterium vitis ondersoek as moontlike gasheerspesifieke transformasie-agente. Rasse van A. vitis behoort uiters geskik te wees vir so "n toepassing, aangesien hulle verskeie unieke eienskappe, wat direk aan die infeksie van die gasheer gekoppel is, vertoon. Van hierdie eienskappe is onder meer die vermoë om tartraat, In koolstofbron volop in druifplante, te benut. A. vitis produseer verder ook In suur poligalaktorunase wat vermoedelik In rol in die infeksieproses speel. Die voorstel dat die evolusionêre ontwikkeling van A. vitis In redelike onlangse gebeurtenis is, word onderskryf deur die betreklike homogenisiteit met A. tumefaciens. In hierdie studie is "n groep A. vitis-rasse met behulp van siftingsprosedures wat daarop gemik is om gesogte eienskappe in rasse uit te wys, beoordeel. Die vermoë om druifplantmateriaal te infekteer (wat vermoedelik "n aanwyser van "n effektiewe meganisme van geenoordraging is wat in "n gemanipuleerde transformasiesisteem benut kan word), sowel as 'n gunstige reaksie (d.w.s geen nekrose) op druifplant somatiese embrio's is van die gesogte eienskappe waarvoor gesoek word. Twee rasse het groot tumors op druifplant-stingelsegmente veroorsaak terwyl hulle bykans geen weefselskade op somatiese embrio's geïnduseer het nie. Betekenisvolle verskille in infektiwiteit en in kallusnekrose is tussen die rasse sowel as in 'n genotipe-spesifieke-verhouding waargeneem. Hierdie genotipe-spesifieke effek, kenmerkend van óf die gasheer óf die patogeen, kan aanduidend wees van die vlak van spesialisasie wat heers by die infeksie van spesifieke gashere. Na aanleiding van bogenoemde resultate was dit moontlik om 'n A. vitis-ras te selekteer wat verder aan biochemiese en genetiese analises onderwerp kon word. Eenvoudige biochemiese analises het dit moontlik gemaak om die ras as oktopien te klassifiseer. DNA-DNA hibridisasietegnieke gekombineerd met 'n unieke plasmiedwandeltegniek het gelei tot die gedeeltelike karakterisering van die geselekteerde A. vitisras. In Gedeeltelike restriksie-ensiem (RE) kaart van die T-DNA kon gevolglik opgestel word. Die T-DNA en die aangrensende gedeeltes is boonop gekloneer. Betekenisvolle verskille, spesifiek die afwesigheid van In TB area, sowel as die afwesigheid van die agrosinopien-sintasegeen (acs) aan die 51-kant van die T-DNA, is waargeneem. Gedeeltelike basispaaropeenvolgingsdata het egter die teenwoordigheid van minstens vier gekonserveerde T-DNA-gene, asook die teenwoordigheid van drie bakteriese invoegingselemente (IS) aan weerskante van die area, geïdentifiseer. Twee van hierdie elemente, wat beide homologie vertoon met die IS110 familie van IS elemente, is nog nie vantevore in A. vitis aangetref nie. Dit wil boonop blyk of dié twee elemente die 51 - en 31 - areas van In onderbroke element vorm, wat dus In moontlike aanduiding is van hul potensiële rol in die evolusionêre ontwikkeling van die ras. Hierdie studie verskaf basiese inligting wat daartoe kan lei dat 'n doeltreffender transformasiesisteem spesifiek vir druifplante ontwikkel word deur van die unieke kenmerke van een van sy patogene, A. vitis, uit te buit.