Search the Health Library
Get the facts on diseases, conditions, tests and procedures.
I Want To...
Find a Doctor
Find a doctor at The Johns Hopkins Hospital, Johns Hopkins Bayview Medical Center or Johns Hopkins Community Physicians.
I Want To...
Find Research Faculty
Enter the last name, specialty or keyword for your search below.
Dome - Scholarly Concentrations course bears fruit
Scholarly Concentrations course bears fruit
Date: June 15, 2012
A classroom anecdote about gin and tonics inspired Alex Harding, now a third-year Hopkins medical student, to conduct research on a water purification method with vast lifesaving potential.
Harding’s research showed that lime juice and sunlight can virtually eradicate E. coli in drinking water in about 30 minutes. Published in April in the American Society of Tropical Medicine and Hygiene, the report was written in collaboration with Kellogg Schwab, a professor in the Bloomberg School of Public Health and director of the JHU Global Water Program.
The student owes his insight to the Scientific Foundations of Medicine course he took in the fall of 2010. He remembers listening as biophysics professor John Lorsch described a class of compounds called psoralens, which are found in limes. These compounds, when combined with UV light, insert themselves into the double helix of DNA, damaging it.
To underscore his point, Lorsch told the class of a dermatologist who would easily recognize the rashes of patients who had been splashed with lime while making gin and tonics out in the sun.
The next morning Lorsch received an email from Harding. The student expressed interest in investigating whether the psoralens in limes could combine with sunlight to destroy contaminants in water, speeding the water purification process known as solar disinfection, or SODIS.
Lorsch recommended that he pursue the topic in Scholarly Concentrations, a course developed for the Genes to Society curriculum that provides guidance and standards as students conduct in-depth research.
“The faculty felt strongly that Hopkins was created as a research-based medical school,” says Lorsch, who served on the committee to reform the curriculum. While Hopkins medical students had conducted research in the past, he says, the addition of Scholarly Concentrations makes it mandatory. The course begins in the middle of a medical student’s first year and concludes when students present their research midway through their second year.
Lorsch helped Harding choose public health as his area of study, and to connect with Schwab.
To set up his experiments, the student would go to the local Safeway at 6 a.m. to buy limes and two-liter soda bottles so that he could begin the five-hour process of preparing the bottles before the midday sun. He filled bottles with water contaminated with E. coli, with water carrying a virus called MS2, and with water containing murine norovirus, considered a surrogate for human norovirus. Some bottles were then left alone, some were treated with synthetic psoralens, and some were treated with lime juice.
Then Harding put the bottles on the deck beside the Cooley pool to disinfect in the Baltimore sun. The number of bottles varied, but was as high as 16 per day, with each combination tested three separate days. “The goal was to replicate field conditions as much as possible,” he says.
His research showed that the combination of sunlight and lime juice could eradicate E. coli in as little as 30 minutes, and reduce the levels of MS2 and norovirus in longer amounts of time. While synthetic psoralens were used to confirm that psoralens were the active chemicals in lime, they are not considered a viable purification choice because they are expensive and not readily available, Harding says. Limes, on the other hand, are cheap and plentiful, particularly in warm countries.
Harding developed an interest in safe drinking water after his sophomore year at Yale, when he worked at a clinic in Muisne, Ecuador. “What really struck me was the number of people, especially children, coming into the hospital with gastrointestinal issues,” he says.
The water coming out of municipal pipes was “green” and unsuitable for drinking, so residents would either boil it or buy bottled water, he says. In the following years, he started a nonprofit that creates municipal water purification systems using filters and chlorine.
With some 850 million people worldwide lacking access to an improved drinking water source, according to a report by UNICEF and the World Health Organization, Harding’s discovery about limes may have far-reaching consequences. At present, the solar disinfection process without psoralens takes about six hours—as many as 48 hours in cloudy weather—while chlorine and other purifying chemicals taste unpleasant and are widely distrusted. Because of its familiar taste and existing reputation as a cleaning agent, Harding says the lime may prove to be a popular solution.
Lorsch says this sort of research is exactly what Scholarly Concentrations was designed to encourage.
“One of the core values of the course is that we want students to take risks and try to do important research,” he said. “It’s not about getting a paper out at the end ... What we really want is to get people excited about doing research in whatever area interests them.”