Evidence for the occurrence of a specific methylammonium transport system in the cultured cyanobiont of the Anthoceros punctatus-Nostoc association

Methylammonium uptake and metabolism was studied in Nostoc sp. ANTH (a free-living cultured isolate from Anthoceros punctatus). Unlike other cyanobacteria, Nostoc sp. ANTH assimilated methylammonium as a fixed nitrogen source. While N₂-grown Nostoc sp. ANTH cells showed ammonium transport characteristics similar to those in other cyanobacteria, a specific energy-dependent methylammonium transport was noticed in methylammonium-grown cells. Unlike methylammonium/ammonium transport in N²-grown cells, methylammonium transport in methylammonium-grown cells was neither affected by ammonium nor by L-methionine-DL-sulphoximine.