Abstract
ABSTRACTGrowth rate, cellular manganese concentration and mangfanese uptake kinetics were measured as functions of the free manganese ion concentration in the medium for two centric diatoms. Thalassiodira oceanica Hasle, isolated from a lou'‐managanese oceanic enviorment. was capable of better growth at low manganese ion concentrations that T. pseudonana hasle and Heimdal, islated from higt.manganese estuatine waters. This was dur to the oceanic species’ greater avility to accumulate manganese at low free ion concentrations and to grow well at lower cellular manganese concentions. Manganese up take in both species followed classical saturation kinestics, and Vmax but not K, Uaried with the managanese ion concentration in the growth medium. The Ks of managanese uptake for T. Oceanica (10‐795 M) was one‐seventh of that for T. Pseudonana. accouning for T. oceanica's greater ablility to accumulate managaese at low gree ion concentrations.Vmax appeared to be under negative feedback control in both species and six‐ to twelve‐fold variations in this parameter allowed cells to regulate cellular managanese at nearly constant valies at manganese ion concentrations in the vicinity of and somewhat below Kr The range in free manganese ion concenteations over which regukation occurred was diffrent for the two species, and coincided with the in free manganese ion concentrations of the natural habitat of each species.
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