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Applied and Environmental Microbiology, December 2007, p. 7882-7890, Vol. 73, No. 24
0099-2240/07/$08.00+0     doi:10.1128/AEM.01097-07
Copyright © 2007, American Society for Microbiology. All Rights Reserved.

Anaerobic 1-Alkene Metabolism by the Alkane- and Alkene-Degrading Sulfate Reducer Desulfatibacillum aliphaticivorans Strain CV2803^T

Laboratoire de Microbiologie, Géochimie et Ecologie Marines, Centre d'Océanologie de Marseille, UMR6117 CNRS, Faculté des Sciences de Luminy, case 901, 13288 Marseille cedex 09,¹ Paléoenvironnements et Paléobiosphère, UMR5125 CNRS, Université Lyon 1, Campus de la Doua, Bâtiment Géode, 69622 Villeurbanne cedex,² Equipe Environnement et Microbiologie, UMR5254 IPREM CNRS, IBEAS Université de Pau et des Pays de l'Adour, BP1155, 64013 Pau cedex,³ GCOM2, UMR6114 CNRS, Faculté des Sciences de Luminy, case 901, 13288 Marseille cedex 09,⁴ Laboratoire de Microbiologie et de Biotechnologie des Environnements Chauds, UMR_D 180, IRD, Universités de Provence et de la Méditerranée, case 925, 13288 Marseille cedex 09, France⁵

Received 16 May 2007/ Accepted 15 October 2007

The alkane- and alkene-degrading, marine sulfate-reducing bacterium Desulfatibacillum aliphaticivorans strain CV2803^T, known to oxidize n-alkanes anaerobically by fumarate addition at C-2, was investigated for its 1-alkene metabolism. The total cellular fatty acids of this strain were predominantly C-(even number) (C-even) when it was grown on C-even 1-alkenes and predominantly C-(odd number) (C-odd) when it was grown on C-odd 1-alkenes. Detailed analyses of those fatty acids by gas chromatography-mass spectrometry after 6- to 10-week incubations allowed the identification of saturated 2- and 4-ethyl-, 2- and 4-methyl-, and monounsaturated 4-methyl-branched fatty acids with chain lengths that correlated with those of the 1-alkene. The growth of D. aliphaticivorans on (per)deuterated 1-alkenes provided direct evidence of the anaerobic transformation of these alkenes into the corresponding 1-alcohols and into linear as well as 10- and 4-methyl-branched fatty acids. Experiments performed with [¹³C]bicarbonate indicated that the initial activation of 1-alkene by the addition of inorganic carbon does not occur. These results demonstrate that D. aliphaticivorans metabolizes 1-alkene by the oxidation of the double bond at C-1 and by the subterminal addition of organic carbon at both ends of the molecule [C-2 and C-(-1)]. The detection of ethyl-branched fatty acids from unlabeled 1-alkenes further suggests that carbon addition also occurs at C-3. Alkylsuccinates were not observed as potential initial intermediates in alkene metabolism. Based on our observations, the first pathways for anaerobic 1-alkene metabolism in an anaerobic bacterium are proposed. Those pathways indicate that diverse initial reactions of 1-alkene activation can occur simultaneously in the same strain of sulfate-reducing bacterium.

Published ahead of print on 26 October 2007.