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Alcaligenesfaecalis (CCT 7145) was isolated from an Amazonian soil sample after an enrichment process to select for phenol-degrading microorganisms. The isolate was labeled with the green fluorescent protein (gfp) gene. The gfp-transformed cells were easily detected using a hand-held UV transilluminator and their taxonomy was confirmed by 16S rRNA sequencing. Polymerase chain reaction (PCR) and Southern blot analyses confirmed that the gfp gene was integrated into the chromosome. The addition of the gfp marker did not affect phenol degradation ability compared with the wild-type. Both, wild-type and gfp-marked A. faecalis cells encapsulated in alginate, tolerated 1,700 microg ml(-1) phenol in liquid medium compared with 1,100 microg ml(-1) phenol for free cells. 14C-Phenol mineralization in soil microcosms was also enhanced by inoculation with encapsulated cells. Survival of gfp-marked cells in phenol-contaminated soil over 22 days was determined from plate counts using an epifluorescence microscope.

Two phenol-degrading microorganisms were isolated from Amazonian rain forest soil samples after enrichment in the presence of phenol and a high salt concentration. The yeast Candida tropicalis and the bacterium Alcaligenes faecoalis were identified using several techniques, including staining, morphological observation and biochemical tests, fatty acid profiles and 16S/18S rRNA sequencing. Both isolates, A. faecalis and C. tropicalis, were used in phenol degradation assays, with Rhodococcus erythropolis as a reference phenol-degrading bacterium, and compared to microbial populations from wastewater samples collected from phenol-contaminated environments. C. tropicalis tolerated higher concentrations of phenol and salt (16 mM and 15%, respectively) than A. faecalis (12 mM and 5.6%). The yeast also tolerated a wider pH range (3-9) during phenol degradation than A. faecalis (pH 7-9). Phenol degradation was repressed in C. tropicalis by acetate and glucose, but not by lactate. Glucose and acetate had little effect, while lactate stimulated phenol degradation in A. faecalis. To our knowledge, these soils had never been contaminated with man-made phenolic compounds and this is the first report of phenol-degrading microorganisms from Amazonian forest soil samples. The results support the idea that natural uncontaminated environments contain sufficient genetic diversity to make them valid choices for the isolation of microorganisms useful in bioremediation.

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