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PCB-chomping microbes festing in harbor muck While scientists fear the effects of toxic PCBs in our food supply, it's good to know something in the muck at the bottom of Charleston Harbor is eating them for us. Something down there is dismantling this man-made substance molecule by molecule and MUSC microbiologist Harold May, Ph.D., wants to find out what it is. He and Kevin R. Sowers, Ph.D., at the University of Maryland Center of Marine Biotechnology are probing harbor mud for microbes that can change the molecular structure of PCBs by metabolizing them and rendering them harmless. PCBs, or polychlorinated biphenyls, were the marvel of modern chemical science for decades until the government banned their production and use in 1977. They don't evaporate, catch fire or explode when hot, and their stability made the oily liquids excellent coolants and insulators in electrical transformers and capacitors. But they were found to pose a serious health threat in the human food supply, and their chemical stability meant they would remain unchanged in the environment for a long time. “Kevin Sowers and I had our ideas, but we couldn't pursue them,” May said. He explained that as graduate students at Virginia Polytechnic Institute and later in their respective careers the two friends communicated their ideas about microorganisms that could clean up hazardous waste. But the time wasn't right. It was when May came to MUSC that he reminded Sowers “of those ideas we talked about.” He said that MUSC's environmental research focus and funding from the Office of Naval Research has made his investigation possible. The two began sampling harbor mud, May in Charleston Harbor and Sowers in Baltimore Harbor, looking for activities in different areas where there was anything that could attack PCBs. They were looking for “anaerobic” organisms that could metabolize PCBs without oxygen. “And we found a bunch. We came across activities that had never been seen before.” May said that he would collect a sample, test it in the lab and then discover a different activity in the harbor mud only a few feet away. The microbes form communities to which he can return and collect more of the same. The communities of microbes include a limited number of species that seem to work together on the PCBs. In the lab, May uses DNA tools developed by Sowers to separate and identify the species and determine which are responsible for the PCB-slicing activities. “We want to know who's out there, what they're doing and how they are doing it. We have evidence that it happens, but we have no sense of the who and how.” One thing May is sure of, there are anaerobic microbes in the harbor mud that like to strip the chlorine off PCBs, and that makes the environment a safer place to live.