Fig. 2.

Full nitrification by N. moscoviensis and urease-negative AOM through reciprocal feeding. (A) Schematic illustration of the proposed reciprocal feeding interaction between ureolytic NOB such as N. moscoviensis (yellow) and urease-negative AOM such as N. europaea (gray). Solid arrows represent conversions of substrates; dashed arrows the uptake or release of substrates. (B) Concentrations of ammonium, nitrite, and nitrate in a coincubation of N. moscoviensis and urease-negative N. europaea during 7 d of incubation with urea as the sole source of energy and nitrogen. The results of two biological replicates are shown for all incubations.