Environmental Internship Program - 2023 Booklet

Tienne Yu ’26
MOLECULAR BIOLOGY
OCEANS AND
ATMOSPHERE
PROJECT TITLE
Molecular Biology of the
Marine Nitrogen Cycle
ORGANIZATION(S)
The Ward Lab,
Department of
Geosciences,
Princeton University
LOCATION(S)
Princeton, New Jersey
MENTOR(S)
Bess Ward,
William J. Sinclair
Professor of Geosciences
and the High Meadows
Environmental Institute;
Samantha Fortin,
Postdoctoral Research
Associate, Geosciences
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.
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