COMMON NITROGEN CONTROL OF CESIUM UPTAKE, CESIUM TOXICITY AND AMMONIUM (METHYLAMMONIUM) UPTAKE IN THE CYANOBACTERIUM NOSTOC-MUSCORUM

Studies were carried out to examine the role of ammonium transport act ivity in the control of caesium uptake and toxicity in Nostoc muscorum . The results showed a definite specific role of the ammonium-repressi ble/derepressible ammonium transport system of the cyanobacterium in c aesium uptake, accumulation and toxicity. Furthermore, the results sho wed that N. muscorum can acquire resistance against diazotrophically-a ssociated caesium toxicity when supplied with ammonium as a nitrogen s ource. In addition, alternatively, a mutant strain was Cs-resistant in the absence of any effect on NH4+-transport, suggesting that Cs+ resi stance may be determined at more than one cellular site.