Furthermore, we detected guanidine in faecal samples from cows, pigs, chicken and sheep and demonstrated guanidine degradation by ammonia-oxidizers in a comammox containing agricultural soil.

Functionally redundant microbes can coexist by partitioning low-concentration substrates even though they compete for one dominant substrate. Thus, the ability to use the low-concentration substrate guanidine provides an additional niche for comammox