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Applied and Environmental Microbiology, August 1998, p. 3014-3022, Vol. 64, No. 8
Department of Microbiology, GBF National
Research Institute for Biotechnology, D-38124 Braunschweig,
Germany,1 and
Laboratorium voor
Microbiologie, Universiteit Gent, B-9000 Ghent,
Belgium2
Received 14 January 1998/Accepted 25 May 1998
A microcosm enrichment approach was employed to isolate bacteria
which are representative of long-term biphenyl-adapted microbial communities. Growth of microorganisms was stimulated by incubating soil
and sediment samples from polluted and nonpolluted sites with biphenyl
crystals. After 6 months, stable population densities between 8 × 109 and 2 × 1011 CFU/ml were established
in the microcosms, and a large percentage of the organisms were able to
grow on biphenyl-containing minimal medium plates. A total of 177 biphenyl-degrading strains were subsequently isolated and characterized
by their ability to grow on biphenyl in liquid culture and to
accumulate a yellow meta cleavage product when they were
sprayed with dihydroxybiphenyl. Isolates were identified by using a
polyphasic approach, including fatty acid methyl ester (FAME) analysis,
16S rRNA gene sequence comparison, sodium dodecyl
sulfate-polyacrylamide gel electrophoresis of whole-cell proteins, and
genomic fingerprinting based on sequence variability in the 16S-23S
ribosomal DNA intergenic spacer region. In all of the microcosms,
isolates identified as Rhodococcus opacus dominated the
cultivable microbial community, comprising a cluster of 137 isolates
with very similar FAME profiles (Euclidean distances, <10) and
identical 16S rRNA gene sequences. The R. opacus isolates from the different microcosms studied could not be distinguished from
each other by any of the fingerprint methods used. In addition, three
other FAME clusters were found in one or two of the microcosms analyzed; these clusters could be assigned to Alcaligenes
sp., Terrabacter sp., and Bacillus
thuringiensis on the basis of their FAME profiles and/or
comparisons of the 16S rRNA gene sequences of representatives. Thus,
the microcosm enrichments were strongly dominated by gram-positive
bacteria, especially the species R. opacus, independent of
the pollution history of the original sample. R. opacus,
therefore, is a promising candidate for development of effective
long-term inocula for polychlorinated biphenyl bioremediation.
0099-2240/98/$04.00+0
Copyright © 1998, American Society for Microbiology. All rights reserved.
Microcosm Enrichment of Biphenyl-Degrading
Microbial Communities from Soils and Sediments
*
Corresponding author. Mailing address: Department of
Microbiology, GBF National Research Institute for Biotechnology,
Mascheroder Weg 1, D-38124 Braunschweig, Germany. Phone:
49-531-6181408. Fax: 49-531-6181411. E-mail: iwd{at}gbf.de.
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