Affinity informs environmental cooperation between ammonia-oxidizing archaea (AOA) and anaerobic ammonia-oxidizing (Anammox) bacteria.

ABSTRACT: Anaerobic ammonia-oxidizing (Anammox) bacteria (AnAOB) rely on nitrite supplied by ammonia-oxidizing bacteria (AOB) and archaea (AOA). Affinities for ammonia and oxygen play a crucial role in AOA/AOB competition and their association with AnAOB. In this work we measured the affinity constants for ammonia and oxygen (half-saturation; k_m) of two freshwater AOA enrichments, an AOA soil isolate (N. viennensis), and a freshwater AnAOB enrichment. The AOA enrichments had similar kinetics (?_max ? 0.36 d^-1, k_m,NH4 ? 0.78?µM, and k_m,O2 ? 2.9?µM), whereas N. viennensis had similar k_m values but lower ?_max (0.23 d^-1). In agreement with the current paradigm, these AOA strains showed a higher affinity for ammonia (lower k_m,NH4; 0.34-1.27?µM) than published AOB measurements (>20?µM). The slower growing AnAOB (?_max ? 0.16 d^-1) had much higher k_m values (k_m,NH4 ? 132?µM, k_m,NO2 ? 48?µM) and were inhibited by oxygen at low levels (half-oxygen inhibition; k_i,O2 ? 0.092?µM). The higher affinity of AOA for ammonia relative to AnAOB, suggests AOA/AnAOB cooperation is only possible where AOA do not outcompete AnAOB for ammonia. Using a biofilm model, we show that environments of ammonia/oxygen counter diffusion, such as stratified lakes, favors this cooperation.

SUBMITTER: Straka LL 

PROVIDER: S-EPMC6775968 | biostudies-literature | 2019 Aug

REPOSITORIES: biostudies-literature