Tienne Yu ’26


Molecular Biology

Project Title

Molecular Biology of the Marine Nitrogen Cycle

I worked with the Ward Lab to study the molecular underpinnings of the marine nitrogen cycle. My project focused on the nirK gene, which is involved in nitrite reduction, and the bacterial 16S gene, which is used to identify bacterial species. I contributed to two projects: a project studying the phylogeny and biogeography of bacterial species carrying the nirK gene, and a project studying nitrite oxidation in oxygen minimum zones, regions of the ocean with persistently low oxygen levels. For the first project, I organized and processed isolation source data of bacterial and archaeal nirK and assisted with creating a phylogenetic tree, a diagram that depicts the lines of evolutionary descent of genes from a common ancestor. For the second project, I optimized a PCR protocol for amplifying the 16S gene in water samples so that it can be sequenced to reveal the identities of the microorganisms within the samples. These results will provide a clearer understanding of how nitrite oxidation occurs in oxygen minimum zones. Through this internship, I gained valuable experience with molecular techniques and data processing and was introduced to oceanography and the marine nitrogen cycle.

Internship Year


Project Category

Oceans and Atmosphere


The Ward Lab, Department of Geosciences, Princeton University - Princeton, New Jersey


Bess Ward, William J. Sinclair Professor of Geosciences and the High Meadows Environmental Institute; Samantha Fortin, Postdoctoral Research Associate, Geosciences