Award Date

August 2016

Degree Type


Degree Name

Master of Science (MS)


Life Sciences

First Committee Member

Brian P. Hedlund

Second Committee Member

Eduardo Robleto

Third Committee Member

Laurel Raftery

Fourth Committee Member

Elisabeth Hausrath

Number of Pages



Members the bacterial genus Thermus have been shown to be incomplete denitrifiers, terminating with nitrite or nitrous oxide (N2O). However, the ability to carry out denitrification and the evolution of nitrogen oxide reductase genes in Thermus remains poorly understood. This study tests the hypothesis that incomplete denitrification is common in Thermus and seeks to uncover patterns in the evolution of denitrification pathways in Thermus. Denitrification capacity was determined in a collection of 25 strains representing ten species of Thermus and phylogenetic analysis was performed to determine whether denitrification genes evolved horizontally in Thermus. No strains in this study reduced nitrate to dinitrogen (N2). Terminal products were nitrite, nitric oxide (NO), or nitrous oxide (N2O), with most strains ending with N2O as a final product. In most cases, denitrification phenotypes were consistent with the presence of denitrification genes and strains of the same species typically had the same denitrification phenotypes. Phylogenetic analysis and the pattern of extant nitrogen oxide reductases showed evidence for horizontal gene transfer (HGT) and gene loss/gain within Thermus. These results show that incomplete denitrification is prominent in the genus Thermus, which suggests Thermus may play a role in consortial denitrification at high temperatures


denitrification; high tempertures; hot springs; microbial ecology; phylogenetics; Thermus


Biology | Environmental Sciences | Microbiology | Terrestrial and Aquatic Ecology

File Format


Degree Grantor

University of Nevada, Las Vegas




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