Fig. 4

Taxonomic dendrograms of the bacterial community detected over a 1-year period in the a black layer and b yellow layer of three reactors. Different taxonomic branches are labeled according to phylum, except Proteobacteria, which was labeled by class. The edges represent the taxonomic path from the root bacteria down to the OTU level (similarity cutoff: 97%). OTUs were located at the lowest possible assignment level, and the node sizes indicated their relative abundance. The nodes are colored according to both their abundance and frequency of occurrence. Red nodes: abundant-persistent (AP) OTUs; blue nodes: abundant-intermediate (AI) OTUs; orange nodes: rare-persistent (RP) OTUs; violet nodes: rare-intermediate (RI) OTUs. The definition of OTUs types was described in subsection “Abundant and persistent bacteria during the biofilm development process”