Fig. 5: Metatranscriptomic response of nitrifying activated sludges to guanidine amendment.
a,b, The transcriptional response of the guanidine APC superfamily permease (APCP) and guanidinase to substrate-spiked (guanidine, ammonium, urea) incubations in abundant comammox organisms from the Ribe (a) and Haderslev (b) WWTPs. Metatranscriptomic reads from the Ribe and Haderslev experiments were mapped to the respective Ribe and Haderslev comammox MAGs; transcriptional levels of the genes of interest are shown in TPM for all timepoints. c,d, Corresponding concentrations of guanidine in the replicate used for metatranscriptomics at time of sampling for Ribe (c) and Haderslev (d). Note that transcripts of the comammox guanidinases were also found at the start of the experiment, although the activated sludge samples had been starved during transport and storage, showing that transcription is either also occurring in the WWTP or that the sludge produced guanidine that was immediately consumed.
