MICROBIAL SUCCESSION DURING A FIELD-EVALUATION OF PHENOL AND TOLUENE AS THE PRIMARY SUBSTRATES FOR TRICHLOROETHENE COMETABOLISM

Microbial community composition and succession were studied in an aqui fer that was amended with phenol, toluene, and chlorinated aliphatic h ydrocarbons to evaluate the effectiveness of these aromatic substrates for stimulating trichloroethene (TCE) bioremediation, Samples were ta ken after the previous year's field studies, which used phenol as the primary substrate, and after three successive monthly treatments of ph enol plus I,l-dichloroethene (1,1-DCE) plus TCE, phenol plus TCE, and toluene plus TCE, Dominant eubacteria in the community were assessed a fter each of the four treatments by characterizing isolates from the m ost dilute most-probable-number tubes and by extracting DNA from aquif er samples, The succession of dominant phenol- and toluene-degrading s trains was evaluated by genomic fingerprinting, cellular fatty acid me thyl ester (FAME) analysis, and amplified ribosomal DNA restriction an alysis (ARDRA). 1,1-DCE was found to drastically reduce microbial grow th and species richness, which corresponded to the reduction in biorem ediation effectiveness noted previously for this treatment (G. D. Hopk ins and P. L. McCarty, Environ. Sci. Technol. 29:1628-1637, 1995), Onl y a few gram-positive isolates could be obtained after treatment with I,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 restor ed until after the subsequent toluene-TCE treatment, Genomic fingerpri nting and FAME analysis indicated that six of the seven originally dom inant microbial groups mere still dominant after the last treatment, i ndicating that the community is quite resilient to toxic disturbance b y 1,1-DCE, FAME analysis indicated that six microbial taxa were domina nt: three members of the beta subclass of the class Proteobacteria (Co mamonas-Variovorax, Azoarcus, and Burkholderia) and three gram-positiv e groups (Bacillus, Nocardia, and an unidentified group), ARDRA reveal ed that the dominant community members were stable during the three no ntoxic treatments and that virtually all of the bands could be account ed for by isolates from Eve of the dominant taxa, indicating that the isolation protocol used likely recovered most of the dominant members of this community.