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Hydrophobicity development, alkane oxidation, and crude-oil emulsification in a Rhodococcus species

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The relationship between the phenomena alkane oxidation, extreme hydrophobicity of the cell surface, and crude-oil emulsification in Rhodococcus sp. strain 094 was investigated. Compounds that induce the emulsifying ability simultaneously induced the cytochrome P450-containing alkane oxidizing system and the transition from low to high cell-surface hydrophobicity. Exposed to inducers of crude-oil emulsification, the cells developed a strong hydrophobic character during exponential growth, which was rapidly lost when entering stationary phase. The loss in hydrophobicity coincided in time with the crude-oil emulsification, indicating that the components responsible for the formation of cell-surface hydrophobicity act as excellent emulsion stabilisers only after release from the cells. Rhodococcus sp. strain 094 possessed three distinct levels of cell-surface hydrophobicity. One level of low hydrophobicity was characteristic of cells in late stationary phase and was independent of growth substrate. A second and more hydrophobic level was observed for cells in exponential phase grown on water-soluble substrates, while a third level, characterised by extreme cell hydrophobicity, was observed for cells in exponential phase cultivated on hydrophobic substrates such as hexadecane. The production of the oil-emulsifying agents seems to require external sources of nitrogen and phosphate.Key words: petroleum, Rhodococcus, seawater, bacteria, bioremediation.

Cette étude a porté sur les relations entre divers phénomènes observés chez la souche 094 de Rhodococcus sp. dont l'oxydation des alcanes, l'extrême hydrophobicité de la surface cellulaire et l'émulsion du pétrole brut. Les composés qui induisent cette capacité d'émulsion du pétrole induisent en même temps le cytochrome P450 responsable du système d'oxydation des alcanes ainsi que de la transition de faible à élevée de l'hydrophobicité de la surface cellulaire. Suite à l'exposition aux inducteurs de l'émulsion du pétrole brut, les cellules acquièrent durant la phase exponentielle de croissance un fort caractère hydrophobe qui est rapidement perdu en début de la phase stationnaire. La perte d'hydrophobicité coïncide dans le temps avec l'émulsion du pétrole, ce qui indique que les composés responsables de l'apparition de cette hydrophobicité de la surface cellulaire agissent comme d'excellents stabilisateurs d'émulsion mais seulement après leur relarguage par les cellules. Les cellules de Rhodococcus sp. souche 094 possèdent trois niveaux distincts d'hydrophobicité de surface. Un niveau d'hydrophobicité faible est caractéristique des cellules en phase stationnaire tardive indépendamment du substrat de croissance. Un deuxième niveau d'hydrophobicité plus élevée peut être rencontré chez les cellules en phase exponentielle cultivées en présence de substrats solubles dans l'eau. Finalement un troisième niveau d'hydrophobicité extrême a pu être observé chez des cellules en phase exponentielle cultivées en présence de substrats hydrophobes comme l'hexadécane. La production d'agents capables d'émulsifier le pétrole brut semble exiger des sources externes d'azote et de phosphate.Mots-clés : Pétrole, Rhodococcus, eau de mer, bactéries, bioremédiation.[Traduit par la Rédaction]

Keywords: Rhodococcus; bacteria; bioremediation; petroleum; seawater

Document Type: Research Article

Publication date: April 1, 2002

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  • Published since 1954, this monthly journal contains new research in the field of microbiology including applied microbiology and biotechnology; microbial structure and function; fungi and other eucaryotic protists; infection and immunity; microbial ecology; physiology, metabolism and enzymology; and virology, genetics, and molecular biology. It also publishes review articles and notes on an occasional basis, contributed by recognized scientists worldwide.
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