Fig. 4

Relative abundance of the bacterial and archaeal partial 16S rDNA genes with phylum (a) and taxon level resolution as low as genus (b) in switchgrass digesters. Fermentation periods are divided by days (D) and residence time (R). The left and right columns are the inoculum (I) and substrate (S) profiles. Only taxa with average relative abundances of greater than 1% are indicated in the legend of b. Steady state with respect to solubilization and gas composition was in general observed at times following change of the feed rate ≥ 3 residence times as described elsewhere. Taxonomic profiles are presented both before and after this 3 residence time threshold. The number of taxonomic profiles made after this threshold for reactors R2 and R3, corresponding to the data to the right for each RT, were as follows: 3 for RT = 20 days, 2 for RT = 10 days, 3 for RT = 5 days, 1 for RT = 3.3 days