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dc.contributor.advisorGermida, James J.en_US
dc.creatorHirkala, Danielle Lynn Marieen_US
dc.date.accessioned2006-11-17T11:15:14Zen_US
dc.date.accessioned2013-01-04T05:08:31Z
dc.date.available2007-11-20T08:00:00Zen_US
dc.date.available2013-01-04T05:08:31Z
dc.date.created2006-11en_US
dc.date.issued2006-11en_US
dc.date.submittedNovember 2006en_US
dc.identifier.urihttp://hdl.handle.net/10388/etd-11172006-111514en_US
dc.description.abstractPseudomonads, particularly the fluorescent pseudomonads, are common rhizosphere bacteria accounting for a significant portion of the culturable rhizosphere bacteria. The presence and diversity of Pseudomonas spp. in the rhizosphere is important because of their ability to influence plant and soil health. Diversity is generated as the result of mutation, the rearrangement of genes within the genome and the acquisition of genes by horizontal transfer systems, e.g. plasmids, bacteriophages, transposons or integrons. The purpose of this study was to examine the phenotypic and genotypic diversity of a subset of pseudomonads (N=133) isolated from the rhizosphere and root-interior of four cultivars of field-grown canola. Pseudomonads were analyzed according to their 16S rRNA and cpn60 gene sequences and selected phenotypic properties (fatty acid methyl ester (FAME) profiles, antibiotic resistance, extracellular enzyme production and carbon substrate utilization). On the basis of 16S rRNA and cpn60 gene sequences, two major clusters were observed, the Pseudomonas fluorescens complex and the P. putida complex. Phylogenetic analysis of the partial gene sequences suggested that the phylogeny of root-associated pseudomonads had no effect on their associations with different cultivars or root zones (i.e. rhizosphere and root interior). Principal component analysis (PCA) of their phenotypic properties revealed little variation among the pseudomonads associated with different canola cultivars. Importantly, while little difference was observed in isolates from different cultivars significant phenotypic variation was observed in isolates from different root zones. Cluster analysis of their phenotypic properties exhibited little correlation with their phylogenetic relationships. In the majority of situations, the isolates grouped into a phylogenetic cluster had less than 75-80% similarity among their phenotypic traits despite a close evolutionary relationship as determined by 16S rRNA and cpn60 gene sequencing. The results indicated that the genotype of the rhizosphere pseudomonads was not accurately reflected in their phenotype. Analysis of the mobile genetic elements (MGEs) associated with a randomly selected subset of the pseudomonad isolates (N=66) revealed that 58% (N=38) contained plasmids, 50% (N=33) contained inducible prophages, 24% (N=16) contained integrons and 23% (N=15) contained transposons. Examination of the MGEs associated with a subset of rhizosphere pseudomonads revealed that MGEs were present in the isolates independent of the degree of similarity between their phenotypic and phylogenetic relationships. Therefore, mutation and genomic rearrangement appear to be the major influences in the observed incongruence between the phylogenetic and the phenotypic relationships of the bacteria examined.en_US
dc.language.isoen_USen_US
dc.subjectmobile genetic elements (MGEs)en_US
dc.subjectPseudomonadsen_US
dc.subjectdiversityen_US
dc.subjecttaxonomicen_US
dc.subjectphenotypicen_US
dc.subjectgeneticen_US
dc.titlePhenotypic and genetic diversity of pseudomonads associated with the roots of field-grown canolaen_US
thesis.degree.departmentApplied Microbiology and Food Scienceen_US
thesis.degree.disciplineApplied Microbiology and Food Scienceen_US
thesis.degree.grantorUniversity of Saskatchewanen_US
thesis.degree.levelDoctoralen_US
thesis.degree.nameDoctor of Philosophy (Ph.D.)en_US
dc.type.materialtexten_US
dc.type.genreThesisen_US
dc.contributor.committeeMemberNelson, Louise M.en_US
dc.contributor.committeeMemberKorber, Darren R.en_US
dc.contributor.committeeMemberKhachatourians, George G.en_US
dc.contributor.committeeMemberDeneer, Harryen_US
dc.contributor.committeeMemberSiciliano, Stevenen_US


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