Eating Volatile Garbage: Bacteria for Bioremediation

There is much in the way of microbial activity that is taking place in one of the world’s poisonous dumps, which turns out to be cleaning up the place.

Take this 150-foot-high garbage dump in Colombia, South America. Soon it may have life as a public park thanks to work from researchers at the University of Illinois and The National University of Colombia in Medellin, who are demonstrating that bacteria in the dump can neutralize numerous contaminants in the soil.

In a press announcement, Jerry Sims, a University of Illinois associate professor of crop sciences and USDA-Agricultural Research Service research leader, working with Andres Gomez, a graduate student from Medellín, Colombia, have experimented with a microbial ecology approach initially proposed by three Medellin professors.

The site of the experiment is a landfill in the Moravia Hill neighborhood of Medellín. This area was formerly a city dump from 1972 to 1984 where thousands of people made a living picking up trash from this dump and built makeshift homes on the land.

“There are some frightening pictures of this site on the Internet,” said Sims. “At one point, close to 50,000 people lived there. They grew vegetables on the contaminated soil and hand-pumped drinking water out of the garbage hill.”

In recent years, the Colombian government has attempted to relocate the people to different neighborhoods with better conditions, while learning if it was possible to clean up the area and turn it into a park. The most reliable solution — digging up the garbage and treating it — was not economically feasible. In addition, there were no records of exactly what was in the dump.

“Apparently, hydrocarbon compounds were one of the main sources of contamination,” said Gomez. “Phenyls, chlorinated biphenyls, and all kinds of compounds that are sometimes very difficult to clean up.”

The three professors from The National University of Colombia in Medellin — Hernan Martinez, Gloria Cadavid-Restrepo and Claudia Moreno — designed an experiment to determine whether bioremediation, which uses biological agents such as bacteria or plants to remove or neutralize contaminants, could be used to clean the site.

Gomez, working on his master’s thesis at the time, collaborated with the trio and was given the task of finding out if there were microorganisms living in the soil that could feed on the carbon in the most challenging contaminants. He analyzed bacteria at different depths in the hill down to 30 meters. He found microbial communities that appeared to have profiles typical of bacteria involved in bioremediation.

Gomez then came to Sims’s lab at the University of Illinois on a grant from the American Society for Microbiology to perform stable isotope probing, a test to link diversity and function that he was not able to do in Colombia. Contaminants are labeled with a heavy isotope that serves as a tracer that can be detected in the end products of biodegradation.

His results confirmed that the bacterial communities had, in fact, been carrying out bioremediation functions. In collaboration with assistant professor of microbial ecology Tony Yannarell who assisted with the microbial diversity analysis, he determined that the organisms involved changed at every depth.

Based on these results, the Colombian government has decided to go ahead with a bioremediation project using the indigenous organisms. One of the professors who worked on the pilot study is looking at ways to provide the microorganisms with extra nutrients to speed up the process. Another possible solution involves a phytoremediation approach, which uses plants to absorb heavy metals.

The results of this experiment can thankfully be shared on a worldwide scale, where thousands of dumps are filled with similar debris.

Source: AAAS EurekAlert 

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