MICROBIAL COMMUNITY REPLICABILITY UNDER A SELECTIVE REGIME IN LAB SCALE ACTIVATED SLUDGE

ERIJMAN, LEONARDO; LOZADA, MARIANA; FIGUEROLA EVA; ITRIA, RAÚL F.

Cancún, México

Congreso; 10th International Symposium on Microbial Ecology (ISME-10).; 2004

International Society for Microbial Ecology

Population dynamics in bacterial communities were examined in replicate lab-scale activated sludge reactors over a period of several months. Four SBR were red with synthetic effiuent, two of which received additionally nonylphenol elhoxylate surfactant. The variability of bacterial communities was investigated by using denaturing gel gradient electrophoresis (DGGE), amplified ribosomal DNA restriction analysis  (ARDRA), partial sequencing of SSU rDNA clones, small-subunit rRNA  oligonucleotide probes and real time PCR. Nested ANOVA was performed to assess variance components for 16S rRNA-directed oligonucleotide probes targeting broad bacterial groups within replicate reactors and between treatments. Differences between treatments were statistically significant (p«O.OO 1) only with regard to probes targeting Betaproteobacteria and Actinobacteria, whereas populations from replicate reactors were not significantly different at high taxonomic levels. Evenness in rRNA clone libraries obtained from control reactors was high, whereas clone libraries from both amended reactors were dominated by two ARDRA types. Their sequences were related to uncultured environmental clones belonging to the Proteobacteria phylum. One of this phylotype also appeared as a co-dominant band in DGGE profiles from NPEO-amended reactors. The sequence of a second dominant DGGE band observed only in test reactors was associated to the Acidobacteria phylum. Specific oligonucleotide probes for the selected ribotypes were designed and applied for real time PCR and 16S rRNA hybridization, confirming their quantitative dominance in treated reactors. The parallel abundance of unique phylotypes in replicate reactors and their constancy over several months suggest that dominant organisms well adapted to specialized niches have been selected and maintained.