Three graduate students from the Bay Paul Center successfully defended their Ph.D. dissertations in the Brown-MBL Partnership and Graduate Program in Biological and Environmental Sciences in the past month.

Susie Theroux defending her dissertation

Susanna Theroux’s doctoral research identified novel species of  algae that can be used to calculate the temperature of lake water going back into geological time. These algae, classified as haptophytes, produce alkenone lipids that function as organic “paleothermometers.” Theroux’s work combined field studies in Greenland and North Dakota, culture studies and DNA sequencing at the MBL, and organic analyses at Brown. She defended her thesis on Nov. 28, and in January she will be starting a postdoctoral fellowship at the Department of Energy’s Joint Genome Institute. Theroux’s Ph.D. advisors were Yongsong Huang of Brown’s Department of Geological Sciences and Linda Amaral-Zettler.

From left: Anupriya Dutta, her advisor David Mark Welch, Linda Amaral Zettler and her advisee Susanna Theroux

Anupriya Dutta studied a remarkable animal lineage that has survived without sexual reproduction over the past 80 million years – the bdelloid rotifers. These microscopic animals can also live for years without water, going into a desiccated state, and can incorporate foreign DNA into their genomes during their dried-out phases. Dutta discovered that bdelloid rotifers have an unusual repertoire of microRNAs (miRNAs) that provides important clues to understanding their asexual evolution, as well as the evolution of miRNAs in animals. Dutta defended her dissertation on Dec. 5; her advisor was David Mark Welch.

Yuko Hasegawa’s doctoral research focused on developing a new imaging technique to see how microbial communities are organized, particularly inside the body. Her technique allows one to distinguish up to 11 different types of microbes in one fluorescence image, which led her to investigate the spatial distributions of bacterial cells in the gut of mice that were inoculated with bacterial types typically found in the human gut. Hasegawa’s imaging protocols will be useful for characterizing spatial organization of microbial communities in many different types of environmental and clinical samples. Her co-advisors were Gary Borisy and Mitchell Sogin; she defended her thesis on December 18.

Yuko Hasegawa in the MBL’s Bay Paul Center. Photo by Tom Kleindinst

The Brown-MBL Graduate Program attracts a diverse group of talented and dedicated students from around the world. Some students spend their first years taking courses at Brown and do not make their base at MBL full-time until their second or third year in the program. Other students remain based in Providence for the duration of their studies but work closely with one or more MBL scientists as they pursue their research. Still other students engage in research that requires them to be at the MBL from the start of their studies. Sixteen graduate students currently are enrolled in the program, ten students have graduated from the program with doctorates and four others have left early with a masters degree.