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The relationship between plants and their root-associated microbial communities in hydrocarbon phytoremediation systems

dc.contributor.advisorGreer, Charles W.en_US
dc.contributor.advisorGermida, James J.en_US
dc.contributor.committeeMemberReynolds, C. Mikeen_US
dc.contributor.committeeMemberKorber, Darren R.en_US
dc.contributor.committeeMemberKnight, J. Dianeen_US
dc.contributor.committeeMemberFarrell, Richard E.en_US
dc.contributor.committeeMemberRoss, Andrew R. S.en_US
dc.creatorPhillips, Lori (Lori Ann)en_US 2008en_US
dc.description.abstractPhytoremediation systems for petroleum hydrocarbons rely on a synergistic relationship between plants and their root-associated microbial communities. Plants exude organic compounds through their roots, which increase the density, diversity and activity of plant-associated microorganisms, which in turn degrade hydrocarbons. Understanding the mechanisms driving this relationship poses one of the more intriguing challenges in phytoremediation research. This study was designed to address that challenge. Plant-microbe interactions in a weathered-hydrocarbon contaminated soil were examined under controlled growth chamber, and field conditions. In both environments single-species grass treatments initially facilitated greater total petroleum hydrocarbon (TPH) degradation than Medicago sativa (alfalfa), mixed species, or control treatments. In growth chamber studies increased degradation was linked to increased aliphatic-hydrocarbon degrader populations within the rhizosphere. Under field conditions, specific recruitment of endophytic aliphatic-hydrocarbon degraders in response to high TPH levels may have facilitated increased degradation by the grass Elymus angustus(Altai wild rye, AWR). AWR stably maintained these communities during times of local drought, enabling them to act as subsequent source populations for rhizosphere communities. The broad phylogenetic diversity of AWR endophytes, compared to the Pseudomonas-dominated communities of other plants, contributed to the observed stability. The relative composition of exudates released by plants also impacted both degradation activity and potential. Alfalfa released higher concentrations of malonate, which hindered degradation by decreasing metabolic activity and concomitantly inhibiting catabolic plasmid transfer. In contrast, AWR exudates contained high levels of succinate, which was linked to increased catabolic gene expression and plasmid transfer. A reciprocal relationship between exudation patterns and endophytic community structure likely exists, and both parameters have a specific influence on rhizosphere degradation capacity. In this study, grasses were more successful in maintaining the specific balance of all parameters required for the transfer, preservation, and stimulation of hydrocarbon catabolic competency.en_US
dc.subjectPlant root exudatesen_US
dc.subjectMicrobial community assessmenten_US
dc.subjectPetroleum hydrocarbonen_US
dc.subjectPlant root endophytesen_US
dc.titleThe relationship between plants and their root-associated microbial communities in hydrocarbon phytoremediation systemsen_US
dc.type.materialtexten_US Scienceen_US Scienceen_US of Saskatchewanen_US of Philosophy (Ph.D.)en_US


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