healthy curiosity
Microbiology students return to shore after collecting samples from pHake Lake.
NANCY HAMLETT
“NO
PHascinating Life Forms
Under the direction of Nancy Hamlett, visiting professor of biology,
Fahmi Quadir ’12 and Heidi Linder ’11 spent the summer characterizing microbial
ONE
diversity in pHake Lake at the Bernard Field Station. In warm months, pHake Lake
stratifies, with the warmer, less dense, oxygenated layer overlying a dense,
sulfide-containing anaerobic layer, which supports a rich microbial community.
KNOWS
Quadir and Linder determined the type of chlorophyll, examined microbial morphology
with fluorescence and phase contrast microscopy, cultivated several types of microbes, and
sequenced DNA of the metagenome. They showed that the layer is dominated by previously
WHAT
uncharacterized ‘green sulfur bacteria’—amazing microbes that carry out photosynthesis in
very dim light, producing sulfur instead of oxygen.
Several other fascinating microbes also inhabit the sulfide layer, including some unknown
THEY
spindle-shaped bacteria that developed a highly refractile central body over the summer—a pro-
cess that was very exciting for the pair to watch. “No one knows what they are,” said Quadir.
Other tasks included determining the morphology of the microorganisms, culturing and puri-
ARE.”
fying dominant life forms and extracting DNA for sequencing in order to better understand the
make-up of the sulfide layer metagenome.
CO
2
rocks
Laura Poindexter ’11 participated in undergrad research through the Science Undergraduate Labo-
ratory Internships (SULI) at Pacific Northwest National Lab, under the mentorship of Zheming
Wang (Senior Scientist). Poindexter prepared pure mineral samples and observed their infrared
spectra. Her research provided supporting evidence that pumping super-critical CO

2
(a hybrid
between a liquid and a gas that exists under high pressure) into a moist, pressurized aquifer or other
deep geological formations underground would convert the CO
2
into carbonate minerals. This is a
potential solution to help curb the effects of mass CO

2
emissions in the earth’s atmosphere.
Carbon dioxide can easily become a super-critical fluid at temperature somewhat higher than
FALL/WINTER 2009 Harvey Mudd College 17
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