Effect of model sorptive phases on phenanthrene biodegradation: Molecular analysis of enrichments and isolates suggests selection based on bioavailability

Reduced bioavailability of nonpolar contaminants due to sorption to natural organic matter is an important factor controlling biodegradation of pollut ants in the environment, We established enrichment cultures in which solid organic phases were used to reduce phenanthrene bioavailability to differen t degrees (R. J. Crosser, M. Friedrich, D. M. Ward, and W. P. Inskeep, AppI . Environ. Microbiol. 66:2695-2702, 2000). Bacteria enriched and isolated f rom contaminated soils under these conditions were analyzed by denaturing g radient gel electrophoresis (DGGE) and sequencing of PCR-amplified 16S ribo somal DNA segments. Compared to DGGE patterns obtained with enrichment cult ures containing sand or no sorptive solid phase, different DGGE patterns we re obtained with enrichment cultures containing phenanthrene sorbed to bead s of Amberlite IRC-50 (AMB), a weak cation-exchange resin, and especially B iobead SM7 (SM7), a polyacrylic resin that sorbed phenanthrene more strongl y. SM7 enrichments selected for mycobacterial phenanthrene mineralizers, wh ereas AMB enrichments selected for a Burkholderia sp, that degrades phenant hrene. 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 Burkholde ria sp, populations, some of which utilized phenanthrene, were detected in sand and control enrichment cultures. Our results are consistent with the h ypothesis that different phenanthrene-utilizing bacteria inhabiting the sam e soils may be adapted to different phenanthrene bioavailabilities.