, 2011); and a late stage (day 112), when the maximum bacterial biomass was measured although phenol oxidase slightly decreased (Fig. 1). The LmPH gene was amplified by PCR from the three leaf litter decomposition stages, and a total number of 148 good quality Bcl-2 expression sequences were obtained from cloning experiments. The estimated rarefaction curves in each sample approached saturation, indicating a good coverage of LmPH gene richness (Fig. 2). All subsequent analyses were performed using an OTU-based approach of the deduced amino acid sequences at a 0.1 cutoff level. The analysis of sequences from the three stages

resulted in 16 different OTUs, nine of them being specific for either the initial or the midterm stage. OTU 14 was the most abundant

and contained LmPH sequences from the initial (11 sequences), the midterm (22), and late (33) stages. The second most abundant Obeticholic Acid molecular weight OTU 3 (12 sequences) was exclusively composed of sequences from the initial stage. Other highly represented OTUs, such as OTUs 15 and 16, grouped exclusively sequences from the midterm and late decomposition stages. The potential functional differences between communities over the course of leaf decomposition were investigated by deducing kinetic properties of bacterial phenol hydroxylases. LmPH genes can be assigned to different functional groups according to changes at selected positions of the amino acid sequence (Futamata et al., 2001). Key amino acid residues at positions 217, 252, and 253 (position numbering based on the Pseudomonas sp. CF600 dmpN gene sequence) may facilitate the prediction of theoretical Michaelis–Menten semi-saturation constants for most uncultured microorganisms

(Viggor et al., 2008). Most of the retrieved sequences (86) belonged to the betaproteobacteria low-Ks LmPH group, previously defined by Futamata et al. (2001) and O-methylated flavonoid grouped separately into clusters A and E (Fig. 3). LmPH sequences in cluster A showed significant similarities (> 80%) to phcN, tbc1D, and afpN genes from Comamonas testosteroni, Burkholderia cepacia, and Alcaligenes faecalis, respectively. On the other hand, cluster E contained LmPH sequences with high similarity with phenol-degrading genes from Comamonas sp. and Alicycliphilus sp. Sequences from the three stages appeared in both clusters, although those from the late stage were less abundant in cluster E. All sequences in cluster B except one (LATE13_E10) were retrieved from the initial and midterm stage samples. Sequences in this cluster exhibited high sequence diversity and grouped into eight different OTUs. Higher similarities (84–94%) were found to LmPH sequences retrieved from noncultured microorganisms from benzene-contaminated soils or trichloroethylene-contaminated aquifers.