Principal coordinate analysis based on the abundances of 16S rRNA gene OTUs (unweighted UniFrac).

<p>For this analysis, observed 16S rRNA gene OTUs were normalized to 1,400 reads per sample. A and H indicate the samples taken from the anaerobic packed-bed (AP) and hybrid packed-bed (HP) reactors. The numbers following A and H indicate days of the operation for biomass sampling.