Researchers at Scripps Institution of Oceanography at UC San Diego and UC San Diego School of Medicine have discovered a widely distributed group of marine bacteria that produce compounds nearly identical to toxic man-made fire retardants.
Among the chemicals produced by the ocean-dwelling microbes, which have been found in habitats as diverse as sea grasses, marine sediments and corals, is a potent endocrine disruptor that mimics the human body's most active thyroid hormone.
The study is published in the June 29 online issue of Nature Chemical Biology.
"We find it very surprising and a tad alarming that flame retardant-like chemicals are biologically synthesized by common bacteria in the marine environment," said senior author Bradley Moore, a professor at Scripps Institution of Oceanography at UC San Diego and the UC San Diego Skaggs School of Pharmacy and Pharmaceutical Sciences.
The toxic compounds are known as polybrominated diphenyl ethers (PBDEs), a subgroup of brominated flame retardants that are combined into foam, textiles, and electronics to raise the temperature at which the products will burn.
Certain formulations of PBDEs are no longer used in automobile and home products in the United States, but testing by the Environmental Protection Agency indicates that most Americans and Canadians carry traces of the chemicals. Indeed, levels exceed those of Europeans and others by a factor of ten or more. Californians, in particular, have higher than average “body burdens” of these compounds.
The study is the first to isolate and identify bacteria that synthesize these compounds and whose presence may help explain the observed distribution pattern of PBDEs in the marine food chain.
Although the presence, persistence, and ability of PBDEs to accumulate in the fatty tissues of marine animals have long been recognized, researchers had previously believed the compounds were anthropogenic in origin and due to ocean pollution.
More recent examinations have shown a pervasiveness of PBDEs in prey and predatory species, suggesting a natural microbial source of the compounds as well as an anthropogenic one.
In the study, the researchers identified a group of ten genes involved in the synthesis of more than 15 bromine-containing polyaromatic compounds, including some PBDEs. They have since conducted DNA sequencing analyses that will allow them to probe the ocean for other biological sources for these chemicals and to begin to assemble a complete picture of their human health risk.
“The next step is to look more broadly in the marine environment for the distribution of this gene signature and to document how these compounds are entering the food chain,” said Vinayak Agarwal, a postdoctoral researcher with the Scripps Center for Oceans and Human Health at UC San Diego.
Co-authors from Scripps (Center for Oceans and Human Health and/or Center for Marine Biotechnology and Biomedicine) include Abrahim El Gamal, Kazuya Yamanaka, Roland Kersten, Dennis Poth, Michelle Schorn, and Eric Allen.
Funding for this study was provided, in part, by the National Science Foundation (grant OCE-1313747) and National Institute of Environmental Health Sciences (grant P01-ES021921) through its Oceans and Human Health program.
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Scripps Institution of Oceanography at the University of California San Diego, is one of the oldest, largest, and most important centers for global science research and education in the world. Now in its second century of discovery, the scientific scope of the institution has grown to include biological, physical, chemical, geological, geophysical, and atmospheric studies of the earth as a system. Hundreds of research programs covering a wide range of scientific areas are under way today on every continent and in every ocean. The institution has a staff of more than 1,400 and annual expenditures of approximately $195 million from federal, state, and private sources. Scripps operates oceanographic research vessels recognized worldwide for their outstanding capabilities. Equipped with innovative instruments for ocean exploration, these ships constitute mobile laboratories and observatories that serve students and researchers from institutions throughout the world. Birch Aquarium at Scripps serves as the interpretive center of the institution and showcases Scripps research and a diverse array of marine life through exhibits and programming for more than 430,000 visitors each year. Learn more at scripps.ucsd.edu and follow us at Facebook, Twitter, and Instagram.
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