title: Anaerobic utilization of toluene by marine alpha- and gammaproteobacteria reducing nitrate.
abstract: Aromatic hydrocarbons are among the main constituents of crude oil and represent a major fraction of biogenic hydrocarbons. Anthropogenic influences as well as biological production lead to exposure and accumulation of these toxic chemicals in the water column and sediment of marine environments. The ability to degrade these compounds in situ has been demonstrated for oxygen- and sulphate-respiring marine micro-organisms. However, if and to what extent nitrate-reducing bacteria contribute to the degradation of hydrocarbons in the marine environment and if these organisms are similar to their well-studied freshwater counterparts has not been investigated thoroughly. Here we determine the potential of marine prokaryotes from different sediments of the Atlantic Ocean and Mediterranean Sea to couple nitrate reduction to the oxidation of aromatic hydrocarbons. Nitrate-dependent oxidation of toluene as an electron donor in anoxic enrichment cultures was elucidated by analyses of nitrate, nitrite and dinitrogen gas, accompanied by cell proliferation. The metabolically active members of the enriched communities were identified by RT-PCR of their 16S rRNA genes and subsequently quantified by fluorescence in situ hybridization. In all cases, toluene-grown communities were dominated by members of the Gammaproteobacteria, followed in some enrichments by metabolically active alphaproteobacteria as well as members of the Bacteroidetes. From these enrichments, two novel denitrifying toluene-degrading strains belonging to the Gammaproteobacteria were isolated. Two additional toluene-degrading denitrifying strains were isolated from sediments from the Black Sea and the North Sea. These isolates belonged to the Alphaproteobacteria and Gammaproteobacteria. Serial dilutions series with marine sediments indicated that up to 2.2×10(4) cells cm(-3) were able to degrade hydrocarbons with nitrate as the electron acceptor. These results demonstrated the hitherto unrecognized capacity of alpha- and gammaproteobacteria in marine sediments to oxidize toluene using nitrate.
authors.affiliation: Ifremer, UMR 6197, Laboratoire de Microbiologie des Environnements Extrêmes (LMEE), Technopôle Pointe du diable, F-29280 Plouzané, France.|Université de Bretagne Occidentale (UBO, UEB), Institut Universitaire Européen de la Mer (IUEM) - UMR 6197, Laboratoire de Microbiologie des Environnements Extrêmes (LMEE), Place Nicolas Copernic, F-29280 Plouzané, France.|NRS, IUEM - UMR 6197, Laboratoire de Microbiologie des Environnements Extrêmes (LMEE), Place Nicolas Copernic, F-29280 Plouzané, France.
authors.forename: Karine
authors.initials: K
authors.lastname: Alain
authors.affiliation: Department of Microbiology, Max Planck Institute for Marine Microbiology, Celsiusstr. 1, D-28359 Bremen, Germany.
authors.forename: Jens
authors.initials: J
authors.lastname: Harder
authors.affiliation: Department of Microbiology, Max Planck Institute for Marine Microbiology, Celsiusstr. 1, D-28359 Bremen, Germany.
authors.forename: Friedrich
authors.initials: F
authors.lastname: Widdel
authors.affiliation: University of California, San Diego, Department of Bioengineering, 9500 Gilman Drive, La Jolla, CA 92093-0412, USA.
authors.forename: Karsten
authors.initials: K
authors.lastname: Zengler
mesh_terms: D020561:Alphaproteobacteria / Q000378:metabolism*; D059001:Aquatic Organisms; D001267:Atlantic Ocean; D059038:Black Sea; D016000:Cluster Analysis; D004269:DNA, Bacterial / Q000737:chemistry / Q000235:genetics; D004275:DNA, Ribosomal / Q000737:chemistry / Q000235:genetics; D020563:Gammaproteobacteria / Q000378:metabolism*; D008522:Mediterranean Sea; D008969:Molecular Sequence Data; D009566:Nitrates / Q000378:metabolism*; D009659:North Sea; D010084:Oxidation-Reduction; D010802:Phylogeny; D012336:RNA, Ribosomal, 16S / Q000235:genetics; D017422:Sequence Analysis, DNA; D014050:Toluene / Q000378:metabolism*
chemical_list: D004269:DNA, Bacterial; D004275:DNA, Ribosomal; D009566:Nitrates; D012336:RNA, Ribosomal, 16S; D014050:Toluene