The green hydra symbiosis and ammonium - IV. Methylammonium uptake by freshly isolated symbionts and cultured algae; evidence for low-ammonium concentration in the perialgal space

Abstract

In comparison to cultured cells of both low and high maltose-releasing strains of symbiotic Chlorella , whether grown or nitrogen starved at high pH (greater than 6), freshly isolated symbionts from all green hydra associations exhibited low rates of uptake of the ammonium analogue methylammonium. However, the high maltose-releasing Chlorella strain 3N813A, maintained at low pH (4-4.5) in the presence of 6-27 μM ammonium had rates of methylammonium uptake and ammonium assimilation which were similar to those of freshly isolated symbionts from the heterologous association E/3N8. It is suggested that symbionts in green hydra and all other alga-invertebrate associations (in the absence of host cell division) are maintained under a low ambient ammonium concentration due to a restricted supply from the host.