Fig. 1

Variation of the nitrogen components over a reaction cycle and sampling points for the metatranscriptomic studies. The 8-hour cycle (480 min, 3 cycles/day) included 6 min feed phase, 450 min reaction phase (divided into 3 aerated and 3 non-aerated phases), 4 min settling phase, 10 min discharge phase, and 10 min idle phase. The replicates for DNA and RNA (S1–S8) extraction were collected from three independent reaction cycles on days 204, 210, and 213