The relative abundance of midas_g_1240 was notably higher in R3 than in the other reactors, possibly due to its role in acidogenesis, which corresponds with the higher VFA concentrations observed in R3 compared to R1 and R2. Several other Firmicutes genera, such as midas_g_184, midas_g_92856, midas_g_148, midas_g_2455, and midas_g_93188, were present only in the biofilm samples of R1.