Effects of diuron in microcosms on natural riverine bacterial community composition: new insight into phylogenetic approaches using PCR-TTGE analysis

. We recently demonstrated in a microcosm study using PCR-TTGE analysis that a realistic diuron exposure (10 μg/L) could directly and indirectly affect the diversity of a natural riverine bacterial community. Here we extended our first approach by identifying predominant bacterial phylotypes in diuron and control microcosms by sequencing and phylogenetic analysis of bands excised from the previously obtained PCR-TTGE gel.We found a sharp difference between phylotypes obtained from the two types of microcosm. Those that appeared or were maintained only in treated microcosms were mainly γ-Proteobacteria, especially the Pseudomonadaceae family, the Verrucomicrobia and the Gemmatimonadetes. In contrast, phylotypes that appeared only in control microcosms belonged to the Chlamydiae. Methodological aspects related to biases encountered after sequence retrieval from fingerprint gels are also discussed.