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Biodegradation 10: 429–435, 1999.
© 2000 Kluwer Academic Publishers. Printed in the Netherlands.
Efficiency of defined strains and of soil consortia in the biodegradation of
polycyclic aromatic hydrocarbon (PAH) mixtures
Murielle Bouchez1;2, Denis Blanchet1, V´eronique Bardin1, Frank Haeseler1 & Jean-Paul
1Institut Français du P´etrole, D´epartement de Microbiologie,92852 Rueil-Malmaison Cedex, France;
2Commissariat `a l’Energie Atomique, Centre de Cadarache, D´epartement d’Entreposage et de Stockage des
D´echets, 13108 Saint-Paul lez Durance Cedex, France
( author for correspondence: e-mail:
Accepted 26 January 2000
Key words: Cometabolism, mixed cultures, PAH degradation, polycyclic aromatic hydrocarbon, soil consortiumAbstract
The microbiological characteristics of the bacterial degradation of mixtures of five polycyclic aromatic hydrocarbons
(PAH), phenanthrene, fluorene, anthracene, fluoranthene and pyrene, were investigated. Three pure bacterial
strains using one or several of these PAH as carbon sources were selected. The interactions between PAH during
the degradation of PAH pairs by each of thesestrains were studied and their effects on the kinetics and the balance
of degradation were characterised. Competition between PAH and degradation by cometabolism were frequently
observed. Mixed cultures of two or three strains, although possessing the global capacity to mineralise the set
of five PAH, achieved limited degradation of the mixture. In contrast, a consortium from a PAH-contaminated
soilreadily mineralised the five-PAH mixture. The results suggested that soil consortia possessed a wider variety
of strains capable to compensate for the competitive inhibition between PAH as well as specialised strains that
mineralised potentially inhibitory PAH metabolites produced by cometabolism.
Detailed knowledge of the degradation of pollutants
in the environment iscritical, in particular, to assess
the persistence of these chemicals in the environment
(Logan & Rittmann 1998). One of the main characteristics
of pollutant hydrocarbons is that they are most
often constituted of mixtures of numerous homologous
compounds. It is known that the biodegradation of
these complex mixtures in the environment involves
various interactions between the components of themixtures and the diverse strains constituting the degradative
microfloræ (Alexander 1965; Perry 1979).
However, our understanding of the modalities and
of the importance of these interactions is still quite
imprecise. Detailed information on these aspects is necessary
to characterise the degradative microfloræ and
evaluate the fate of these hydrocarbon mixtures.
Polycyclic aromatichydrocarbons (PAH) constitute
an important class of such compounds. Because
of their genotoxicity and of their ubiquitous distribution,
their biodegradation is an actively investigated
field (Cerniglia 1993; Bouchez et al. 1996b). Bacterial
strains, using as sole carbon and energy sources, PAH
possessing up to 4 cycles, have been isolated, and it
has been shown that each of these strains was capableof using a limited, although variable, range of PAH
as carbon sources (Boldrin et al. 1993; Bouchez et
al. 1995; Kästner et al. 1994; Mueller et al. 1990).
Considering a given strain, PAH not used as substrates
were rather frequently found to interact with
the degradation of the PAH used as carbon source, in
particular, through competitive inhibition and cometabolism
(Bouchez et al. 1995;Mueller et al. 1990;
Stringfellow & Aitken 1995). The present work is
aimed at a better understanding of the degradation
of PAH mixtures, by comparing the performance of
defined mixed cultures with that of natural consortia.
We studied the effects of PAH interactions in the degradation
of a mixture of five PAH. Three bacterial
strains with different ranges of PAH substrates covering...