Scores of bacteria live on the many surfaces of the Baltimore-area subway and light rail systems, and three University of Maryland School of Medicine scientists set out Wednesday to learn more about the microscopic organisms found there.
Emmanuel F. Mongodin, Lynn M. Schriml and Lauren Hill, microbe researchers at the medical school's Institute for Genome Sciences, began their mission at the Charles Center Metro stop in downtown Baltimore.
There they and a group of student volunteers used synthetic swabs to wipe handrails, ticket kiosks and floors to collect samples of bacteria. They placed the swabs in tubes that will be sent to a New York lab for DNA and RNA sequencing and analysis.
The research is part of a global project started last year by Weill Cornell Medicine in New York to collect and catalogue bacteria in public transportation systems around the world. Researchers descended on more than 50 cities Wednesday swabbing for samples.
The information will be used to develop a giant genetic map, or microbiome, that details the community of microorganisms that live on the surfaces of transportation hubs.
That information could be used to aid in new drug discoveries and influence the way transportation systems of the future are built. It will also allow scientists to better study antimicrobial resistance and potentially make cities safer, the researchers said.
"We really want to understand how these microbes interact and move around," Schriml said.
Cornell first did testing for bacteria in subways in New York two years ago and expanded globally last year.
Baltimore had a small pilot program last year to figure out logistics and protocols. This year, they did a full-scale collection at all 14 Metro subway stations and a handful of light rail stations.
A human body contains about 50 trillion to100 trillion bacterial cells, said Dr. Christopher Mason, principal investigator on the global project. The number on subway systems, by comparison, "is almost certainly in the 100s of trillions," he said
Researchers discovered lots of food bacteria. One sample included a large amount of chickpeas and cucumber. Researchers guessed that people were eating falafel. "A huge amount of it," Mason said.
In New York, scientists found fish and other bacteria related to the ocean in one station that had flooded during Hurricane Sandy. They were also able to learn the ancestry of people who used the stations based on the human DNA left behind. An area of North Harlem in New York had a strong mix of African-American and Hispanic genes.
Riders looked perplexed as the University of Maryland scientists wearing green rubber gloves swirled their swabs on various parts of the subway.
"I would hate to see what's on this seat," said 33-year-old Melissa Meissinger, who was riding the subway from Johns Hopkins Hospital.
"Ewww, scary!" said Curtis Rice, a 56-year-old retiree who was coming into the Charles Center station.
The scientists said that is a common reaction. But the research from other subways systems shows that most of the bacteria are actually good and not harmful to humans. Harmful bacteria are usually found in trace amounts or disappear quickly.
"There's nothing nasty in the subways," Schriml said. "They're clean. They're cleaner than bathrooms."
Said Cornell's Mason: "Most people have relatively healthy skin microbiome, and that is what they leave behind."
Researcher say the project should serve as a lesson to people that exposure to bacteria helps build up immune systems.
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Baltimore Mayor Catherine Pugh was on hand Wednesday to try her hand at swabbing. She said that although the subways are cleaned regularly, it's easy to see how people might think they are dirty because the systems handle so many people.
"We have to learn not to be such germaphobes and realize that some bacteria is good for us," she said.
The Maryland researchers plan to publish a report on their findings in the next few months.
Rice is looking forward to the results. Although he still thinks subways are dirty, he believes his body has built up resistance to all that bacteria.
"I take public transportation all the time, and I never get sick," he said.