title: Isolation and characterization of a novel sphingomonad capable of growth with chrysene as sole carbon and energy source.
abstract: A bacterial strain able to grow in pure culture with chrysene as sole added carbon and energy source was isolated from PAH-contaminated soil after successive enrichment cultures in a biphasic growth medium. Initially, growth occurred in the form of a biofilm at the interface between the aqueous and non-aqueous liquid phases. However, after a certain time, a transition occurred in the enrichment cultures, with growth occurring in suspension and a concomitant increase in the rate of chrysene degradation. The strain responsible for chrysene degradation in these cultures, named Sphingomonas sp. CHY-1, was identified by 16S rDNA sequencing as a novel sphingomonad, the closest relative in the databases being Sphingomonas xenophaga BN6T (96% sequence identity). Both these strains clustered with members of the genera Sphingobium and Rhizomonas, but could not be categorically assigned to either genus. Sphingomonas sp. CHY-1 was characterized in terms of its growth on chrysene and other PAH, and the kinetics of chrysene degradation and 14C-chrysene mineralization were measured. At an initial chrysene concentration of 0.5 g l(-1) silicone oil, and an organic/aqueous phase ratio of 1:4, chrysene was 50% degraded after 5 days incubation and 97.5% degraded after 35 days. The protein content of cultures reached a maximum value of 11.5 microg ml(-1) aqueous phase, corresponding to 92 mg g(-1) chrysene. 14C-labelled chrysene was 50% mineralized after 6-8 weeks incubation, 10.7% of the radioactivity was incorporated into cell biomass and 8.4% was found in the aqueous culture supernatant. Sphingomonas sp. CHY-1 also grew on naphthalene, phenanthrene and anthracene, and naphthalene was the preferred substrate, with a doubling time of 6.9 h.
authors.affiliation: Laboratoire de Biochimie et Biophysique des Systèmes Intégrés (UMR 5092 CNRS-CEA-UJF), DRDC/BBSI, CEA-Grenoble, 17 rue des Martyrs, 38054 Grenoble Cedex 9, France. jwillison@cea.fr
authors.forename: John C
authors.initials: JC
authors.lastname: Willison
mesh_terms: D001673:Biodegradation, Environmental; D018441:Biofilms / Q000254:growth & development; D002911:Chrysenes / Q000378:metabolism*; D003470:Culture Media; D004275:DNA, Ribosomal / Q000032:analysis; D008969:Molecular Sequence Data; D011084:Polycyclic Aromatic Hydrocarbons / Q000378:metabolism; D012336:RNA, Ribosomal, 16S / Q000235:genetics; D017422:Sequence Analysis, DNA; D012988:Soil Microbiology; D012989:Soil Pollutants / Q000378:metabolism*; D020578:Sphingomonas / Q000145:classification* / Q000254:growth & development / Q000302:isolation & purification* / Q000378:metabolism
chemical_list: D002911:Chrysenes; D003470:Culture Media; D004275:DNA, Ribosomal; D011084:Polycyclic Aromatic Hydrocarbons; D012336:RNA, Ribosomal, 16S; D012989:Soil Pollutants; C031180:chrysene