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Appl. Environ. Microbiol., Apr 1997, 1515-1522, Vol 63, No. 4
MR Fries, GD Hopkins, PL Mccarty, LJ Forney and JM Tiedje
Microbial community composition and succession were studied in an aquifer
that was amended with phenol, toluene, and chlorinated aliphatic
hydrocarbons to evaluate the effectiveness of these aromatic substrates for
stimulating trichloroethene (TCE) bioremediation. Samples were taken after
the previous year's field studies, which used phenol as the primary
substrate, and after three successive monthly treatments of phenol plus
1,1-dichloroethene (1,1-DCE) plus TCE, phenol plus TCE, and toluene plus
TCE. Dominant eubacteria in the community were assessed after each of the
four treatments by characterizing isolates from the most dilute
most-probable-number tubes and by extracting DNA from aquifer samples. The
succession of dominant phenol- and toluene-degrading strains was evaluated
by genomic fingerprinting, cellular fatty acid methyl ester (FAME)
analysis, and amplified ribosomal DNA restriction analysis (ARDRA). 1,1-DCE
was found to drastically reduce microbial growth and species richness,
which corresponded to the reduction in bioremediation effectiveness noted
previously for this treatment (G. D. Hopkins and P. L. McCarty, Environ.
Sci. Technol. 29:1628-1637, 1995). Only a few gram-positive isolates could
be obtained after treatment with 1,1-DCE, and these were not seen after any
other treatments. Microbial densities returned to their original levels
following the subsequent phenol-TCE treatment, but the original species
richness was not restored until after the subsequent toluene-TCE treatment.
Genomic fingerprinting and FAME analysis indicated that six of the seven
originally dominant microbial groups were still dominant after the last
treatment, indicating that the community is quite resilient to toxic
disturbance by 1,1-DCE. FAME analysis indicated that six microbial taxa
were dominant: three members of the (beta) subclass of the class
Proteobacteria (Comamonas-Variovorax, Azoarcus, and Burkholderia) and three
gram-positive groups (Bacillus, Nocardia, and an unidentified group). ARDRA
revealed that the dominant community members were stable during the three
nontoxic treatments and that virtually all of the bands could be accounted
for by isolates from five of the dominant taxa, indicating that the
isolation protocol used likely recovered most of the dominant members of
this community.
Copyright © 1997, American Society for Microbiology
Microbial Succession during a Field Evaluation of Phenol and Toluene as the Primary Substrates for Trichloroethene Cometabolism
Center for Microbial Ecology and Departments of Crop and Soil Sciences and of Microbiology, Michigan State University, East Lansing, Michigan 48824, and Department of Civil Engineering, Stanford University, Stanford, California 94305
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