In Hanahan, South Carolina, just a few miles north of Charleston, sitsthe Defense Fuel Supply Center _ a jet-fuel tank farm. A residentialneighborhood nearby is too close for comfort to the contaminationcaused by inadvertent leakage and spillage of aromatic hydrocarbonsfrom the underground fuel-storage facility.A task force of the U.S. Geological Survey (USGS) in Reston, Va. isstudying ways to remove the toxic, soluble benzene, toluene andxylenes from groundwater into which they have seeped. The team'snovel clean-up agent is the natural population of anaerobic bacteria,which live on the carbon they obtain by degrading such petroleumpollutants to carbon dioxide.To capture these carbon atoms, current aerobic microbes need plenty ofoxygen, an element hard to find in a shallow aquifer. Bioremediatorsoften pump oxygen into the groundwater to stimulate biodegradation,but this is a difficult, expensive expedient.The anaerobic bacteria consume iron instead of oxygen. However,ferric iron salts in the contaminated sub-surface water-bearing geologicformation are insoluble, hence inedible. How to make them accessibleto the microorganisms is a challenge being met by USGSmicrobiologist Derek Lovley.In this week's Nature, he reports "Stimulated anoxic biodegradation ofaromatic hydrocarbons using Fe(III) ligands.""What's new in this paper," Lovley told BioWorld Today, " is thatthese ferric ligands _ organic compounds that bind to the iron oxide_ make the oxide available to the microorganisms." He added, "Thenthey can degrade the aromatic hydrocarbons just as fast as it happenswith aerobes in the presence of oxygen."Lovley is project chief of USGS's Microbial Geochemical Modelsprogram.Oxygen, he explained, is an electron acceptor. "Most organisms,ourselves included, oxidize organic compounds _ get our energy _by transferring electrons to oxygen. So our electron donor is someorganic compound like sugar, and the electron acceptor is oxygen,reduced to water.""The anaerobic microorganisms in the aquifer," he continued, "insteadof breathing oxygen, breath iron. They reduce the oxide form of iron,ferric iron, Fe(III) to ferrous iron, Fe(II). They're putting an electrononto the iron."To make this happen, the team introduced a metal-combining chelationagent, NTA (nitrilotriacetic acid), to serve as electron donor. NTA'sbinding onto the Fe(III) oxide, the Nature paper reported, permitted thenative, anaerobic microorganisms to reduce the Fe(III) much faster."The bacterium, in question," Lovley said, is probably Geobactermetallireducens, the first organism of any kind able to degrade anaromatic hydrocarbon _ even notoriously refractory benzene _ in theabsence of oxygen." That bug, he said, was originally isolated frombottom sediments in the Potomac river, and a closely related strain wasrecently recovered from the Hanahan aquifer.So far, his microbial geochemical team has merely stimulated thebacterium's activity in the laboratory, on contaminated soil andgroundwater samples from the Hanahan tank farm. Eventually, it plansto enhance the microbes' performance by recombinant DNAtechnology. "We haven't begun to develop a genetic system for theorganism yet; it depends on funding," Lovley said. "It's not related toE. coli, the standard cloning host, so it's going to take a little bit ofdevelopment, just finding vectors and so on. First we've got to learnmore about its physiology; how it reduces metal."Meanwhile, USGS has applied for a patent on the system, for which itwould like to find a commercial partner. "The Geologic Survey,"Lovley observed, "is not in the bioremediation business. We'd like tocollaborate with somebody who is."This receptivity to industry is a new development in itself. "Until ourpaper came out in Nature last Thursday, and became publicknowledge," he explained, "we were not allowed to discuss it withanyone."The technique, Lovley concluded, "can also concentrate uranium fromcontaminated soils. As with our hydrocarbon degradation studies, wehave demonstrated its effectiveness only on the lab scale, and would beinterested in working with an appropriate company to scale up thisuranium procedure too."One bioremediator that pumps oxygen into gasoline-polluted groundwater to feed aerobic bacteria is the Shell Oil Company. MicrobiologistJoseph Salanitro of Shell's environmental research department isfamiliar with Lovley's anaerobic experiments."I think his paper addresses benzene," Salanitro told BioWorld Today."If benzene is degraded under anaerobic conditions with iron-reducingbacteria, it's a first, but not for other aromatics."Salanitro cautions however about the use of toxic chelating agents suchas NTA: "One of the problems is that you're not allowed to addorganic chemicals to ground- water, which is what would have tohappen here."Lovley said that he is switching from NTA to the more benign chelator,EDTA (ethylenediaminetetraacetic acid). It has clinical uses, sopresumably would be acceptable in his anaerobic decontaminationtechnique. n
AMEX Replaces Five StocksIn Biotech IndexIn an effort to more accurately reflect changes in the biotechnologyindustry, the American Stock Exchange has replaced five of the 15stocks in its Biotechnology Index. The new index became effective asof the close of trading on Friday, July 15.The five new stocks include Cor Therapeutics Inc. (CORR), CellProInc. (CPRO), Cephalon Inc. (CEPH); Vertex Pharmaceuticals Inc.(VRTX) and Protein Design Labs Inc. (PDLI). They are replacingXoma Corp. (XOMA), Enzon Inc. (ENZN), RegeneronPharmaceuticals Inc. (REGN), Cytogen Corp. (CYTO) and TheLiposome Company (LIPO).AMEX said that it dropped the five stocks because they fell in priceover time and/or had failed to meet the minimum market capitalizationrequirement of $75 million, or were no longer deemed representative ofthe biotechnology industry as a whole.The AMEX Biotechnology Index, which is equal-dollar-weighted, nowincludes the following companies:Amgen Inc. (AMGN), Biogen Inc. (BGEN), Calgene Inc. (CGNE),CellPro Inc. (CPRO), Centocor Inc. (CNTO), Cephalon Inc. (CEPH),Chiron Corp. (CHIR), Cor Therapeutics (CORR), Gensia Inc.(GNSA), Genzyme Corp. (GENZ), The Immune Response Corp.(IMNR), Protein Design Labs Inc. (PDLI), Scios Nova Inc. (SCIO),Synergen Inc. (SYGN) and Vertex Pharmaceuticals Inc. (VRTX). Allstocks are listed on the NASDAQ National Market.The Chicago Board of Exchange, on the other hand, has not yet alteredany of the listings on its own BioTech Index _ although it is currentlyreviewing possible changes. The CBOE BioTech Index is a price-weighted index of 20 companies whose stocks were picked to berepresentative of small- and medium-cap stocks in the biotech sector. Itincludes:Amgen Inc. (AMGN), Biogen Inc. (BGEN), Bio-technology GeneralCorp. (BTGC), Calgene Inc. (CGNE), Centocor Inc. (CNTO), ChironCorp. (CHIR), Cytogen Corp. (CYTO), Enzon Inc. (ENZN), EpitopeInc. (EPT), Gensia Inc. (GNSA), Genzyme Corp. (GENZ), GreenwichPharmaceuticals Inc. (GRPI), The Immune Response Corp. (IMNR),Immunex Corp. (IMNX), Immunomedics Inc. (IMMU), Ivax Corp.(IVX), The Liposome Co. Inc. (LIPO), North American Vaccine Inc.(NVX), Synergen Inc. (SYGN) and Xoma Corp. (XOMA). _ JenniferVan Brunt
-- David N. Leff Science Editor
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