Abundance of clones and OTUs. Distribution of the clones and OTUs in taxonomic groups and their abundance in the individual samples are displayed. Number of clones per season in the largest phyla is indicated in the row with the name of the phylum. 1, Building 1; 2, Building 2; W, winter; Sp, spring; Su, summer; F, fall. Uncultured refers to sequences of species not yet cultured; unknown refers to a sequence similarity less than 95% to a database sequence, however if the clone was clearly affiliated to a certain group in the phylogenetic tree, it was assigned to that group. In addition to the clones listed in the figure, there was one clone in Building 2, summer sample affiliating with Planctomycetes, one clone in Building 1, spring sample affiliating with Chloroflexi, and one clone with unknown phylogenetic affiliation in Building 1, winter and fall samples. The grey shading indicates the number of clones in the sample belonging to the respective family. White indicates zero clones, the grey shadings 1, 2–5, or 6–14 clones, and black indicates 15 or more clones.