title: Initial characterization of new bacteria degrading high-molecular weight polycyclic aromatic hydrocarbons isolated from a 2-year enrichment in a two-liquid-phase culture system.
abstract: OBJECTIVE
  To characterize some polycyclic aromatic hydrocarbons (PAH)-degrading microorganisms isolated from an enriched consortium degrading high molecular weight (HMW) PAHs in a two-liquid-phase (TLP) soil slurry bioreactor, and to determine the effect of low molecular weight (LMW) PAH on their growth and HMW PAH-degrading activity.
  
  
  RESULTS
  Several microorganisms were isolated from a HMW-PAH (pyrene, chrysene, benzo[a]pyrene and perylene) degrading consortium enriched in TLP cultures using silicone oil as the organic phase. From 16S rRNA analysis, four isolates were identified as Mycobacterium gilvum B1 (99% identity),Bacillus pumilus B44 (99% identity), Microbacterium esteraromaticum B21 (98% identity), and to the genus Porphyrobacter B51 (96% identity). The two latter isolates have not previously been associated with PAH degradation. Isolate B51 grew strongly in the interfacial fraction in the presence of naphthalene vapours and phenanthrene compared with cultures without LMW PAHs. Benzo[a]pyrene was degraded in cultures containing a HMW PAH mixture but pyrene had no effect on its degradation. The growth of isolates B1 and B21 was improved in the aqueous phase than in the interfacial fraction for cultures with naphthalene vapours. Pyrene was required for benzo[a]pyrene degradation by isolate B1. For isolate B21, pyrene and chrysene were degraded only in cultures without naphthalene vapours.
  
  
  CONCLUSIONS
  Consortium enriched in a TLP culture is composed of microorganisms with different abilities to grow at the interface or in the aqueous phase according to the culture conditions and the PAH that are present. Naphthalene vapours increased the growth of the microorganisms in TLP cultures but did not stimulate the HMW PAH degradation.
  
  
  CONCLUSIONS
  New HMW PAH-degrading microorganisms and a better understanding of the mechanisms involved in HMW PAH degradation in TLP cultures.
authors.affiliation: INRS-Institut Armand-Frappier, Université du Québec, Québec, Canada.
authors.forename: E
authors.initials: E
authors.lastname: Gauthier
authors.forename: E
authors.initials: E
authors.lastname: Déziel
authors.forename: R
authors.initials: R
authors.lastname: Villemur
authors.forename: P
authors.initials: P
authors.lastname: Juteau
authors.forename: F
authors.initials: F
authors.lastname: Lépine
authors.forename: R
authors.initials: R
authors.lastname: Beaudet
mesh_terms: D001419:Bacteria / Q000235:genetics / Q000302:isolation & purification* / Q000378:metabolism; D001580:Benzopyrenes / Q000494:pharmacology; D001673:Biodegradation, Environmental; D002911:Chrysenes / Q000494:pharmacology; D003470:Culture Media; D008970:Molecular Weight; D009281:Naphthalenes / Q000494:pharmacology; D011084:Polycyclic Aromatic Hydrocarbons / Q000378:metabolism*; D016133:Polymerase Chain Reaction / Q000379:methods; D011721:Pyrenes / Q000494:pharmacology; D012336:RNA, Ribosomal, 16S / Q000235:genetics; D017423:Sequence Analysis, RNA / Q000379:methods; D018505:Waste Management / Q000379:methods
chemical_list: D001580:Benzopyrenes; D002911:Chrysenes; D003470:Culture Media; D009281:Naphthalenes; D011084:Polycyclic Aromatic Hydrocarbons; D011721:Pyrenes; D012336:RNA, Ribosomal, 16S; C031180:chrysene; C031721:naphthalene; C030984:pyrene