PCR and LDR/Universal Array approach. Complete experimental procedures concerning the amplification of 16S rRNA sequences (including primers and thermal cycling), LDR mixes, Universal Arrays preparation and hybridization are reported in Supplementary Data. Data analysis. All arrays were scanned with ScanArray 5000 scanner (Perkin Elmer Life Sciences, Boston, MA, USA), at 10 mm resolution, with different acquisition parameters on both laser power and photo-multiplier gain, in order to avoid saturation. Intensities of fluorescence (IF) were quantitated by ScanArray Express 3.0 software, using the 'Adaptive circle' option, letting diameters vary from 60 to 300 mm. No normalization procedures on the IFs were performed.