Fig. 3

Principal coordinate analysis (PCoA) scatter plot of 16S rRNA sequences based on the weighted UniFrac obtained by Illumina sequencing of the same number of sequences (40,525) of 25 samples from each depth of the bioreactor under the neutral (a) and acid (b) conditions. The depth of the bioreactor is as follows: top, closed squares; port 1, hatched squares; port 2, gray squares; port 3, plaid squares; port 4, open squares. Arrows indicate the direction from top to bottom of the bioreactor. The numbers beside the plots indicate their respective HRTs