Applied and Environmental Microbiology, 2000
Reduced bioavailability of nonpolar contaminants due to sorption to natural organic matter is an important
factor controlling biodegradation of pollutants in the environment. We established enrichment cultures in
which solid organic phases were used to reduce phenanthrene bioavailability to different degrees (R. J. Grosser,
M. Friedrich, D. M. Ward, and W. P. Inskeep, Appl. Environ. Microbiol. 66:2695–2702, 2000). Bacteria
enriched and isolated from contaminated soils under these conditions were analyzed by denaturing gradient
gel electrophoresis (DGGE) and sequencing of PCR-amplified 16S ribosomal DNA segments. Compared to
DGGE patterns obtained with enrichment cultures containing sand or no sorptive solid phase, different DGGE
patterns were obtained with enrichment cultures containing phenanthrene sorbed to beads of Amberlite
IRC-50 (AMB), a weak cation-exchange resin, and especially Biobead SM7 (SM7), a polyacrylic resin that
sorbed phenanthrene more strongly. SM7 enrichments selected for mycobacterial phenanthrene mineralizers,
whereas AMB enrichments selected for a Burkholderia sp. that degrades phenanthrene. Identical mycobacterial
and Burkholderia 16S rRNA sequence segments were found in SM7 and AMB enrichment cultures inoculated
with contaminated soil from two geographically distant sites. Other closely related Burkholderia sp. populations,
some of which utilized phenanthrene, were detected in sand and control enrichment cultures. Our results
are consistent with the hypothesis that different phenanthrene-utilizing bacteria inhabiting the same soils may
be adapted to different phenanthrene bioavailabilities.
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