Dynamics of bacterial taxonomic compositions in response to OLR manipulation. (a) principal coordinate analysis (PCoA) of control and co-digestion samples. Control and co-digestion samples are indicated by red circles and blue squares, respectively, with the gradient of color representing sampling time. (b) Taxa classification at the phylum level of the four groups of OTUs: abundant OTUs across all samples (Group 1); OTUs enriched under co-digestion (Group 2); OTUs declined under co-digestion (Group 3); and the ‘all’ group representing all the OTUs detected. (c) The mean of estimated rRNA operon copy number of OTUs for each group. The error bar represents standard error. Values with different superscript letters at each group are significantly (P<0.05) different from each other.