USE OF METHYLAMMONIUM AS AN AMMONIUM ANALOGUE IN NITROGEN TRANSPORT AND ASSIMILATION STUDIES WITHCYCLOTELLA CRYPTICA(BACILLARIOPHYCEAE)1

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Abstract
The effect of methylammonium on the utilization of other nitrogen sources and the characteristics of methylammonium uptake byCyclotella crypticaReimann, Lewin, and Guillard were examined. Methylammonium prevented growth on nitrate, nitrite, and arginine, but did not affect growth on ammonium or glutamine. Methylammonium was taken up rapidly by what appears to be an ammonium transport system. Transport followed saturable kinetics, was specific for ammonium and methylammonium, and appeared to be subject to nitrogen regulation. Transport rates were hyperbolically related to external Na+and strongly inhibited by high external concentrations of K+. These results support the use of methylammonium as an ammonium analogue, as an inhibitor of the utilization of some forms of nitrogen, and in the analysis of the mechanism and regulation of ammonium transport.