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Date Permissions Signed


Date of Award


Document Type

Masters Thesis

Degree Name

Master of Science (MS)



First Advisor

Moyer, Craig L.

Second Advisor

Leaf, David Scott, 1955-

Third Advisor

Young, Jeff C. (Jeffery C.)

Fourth Advisor

Schwarz, Dietmar, 1974-


Thermococcus are an Archaeal genus of hyperthermophilic microorganisms found to be ubiquitously present in hydrothermal habitats. DNA analyses of Thermococcus isolates focusing primarily on isolates from the Juan de Fuca Ridge, Gorda Ridge, and South East Pacific Rise, were applied in order to determine the relationship between geographic distribution and relatedness. Amplified fragment length polymorphism (AFLP) analysis and multilocus sequence typing (MLST) were used to resolve genomic differences at the species and strain level in 90 isolates of Thermococcus, allowing for the detection of biogeographic patterns and evolutionary relationships within this genus. Isolates were differentiated at regional levels and into distinct lineages within regions. Although no correlation was found between environmental characteristics and genotype, the presence of distinct lineages within the same vent site suggests the utilization of different ecological niches by distinct Thermococcus species. A unique group of Thermococcus identified, that lacked geographic genetic structure, contained highly similar isolates from disparate regions. The anomalous nature of this group may be explained by a recent population divergence, having high dispersal potential or possibly in being a niche specific ecotype. In addition to the resolution of biogeographic patterns and evolution in Thermococcus that this study has provided, new questions have been raised about the closely related Pyrococcus genus. Analysis of loci GC ratios and the placement of Pyrococcus type strains in phylogenetic trees have demonstrated the close association between Thermococcus and Pyrococcus and the unresolved divergence between these two genera.




Western Washington University

OCLC Number


Digital Format


Geographic Coverage

Pacific Ocean


Academic theses




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