SUMMARY: Mycelium of harvested in mid-logarithmic phase absorbs Zn from dilute solutions in the absence of growth. Zn uptake involves two phases: a rapidly established phase 1 believed to represent adsorption to negatively charged groups in the hyphal surface-membrane and a slowly established phase 2 which represents transport into the cytoplasm. Phase 1 is not influenced by low temperature, NaN or anaerobiosis applied for short periods, conforms to the Langmuir adsorption equation and is reduced in the presence of various other divalent cations. Phase 2 is strongly inhibited by low temperature, NaN and anaerobiosis and exhibits carrier-type kinetics with an apparent for Zn of 0.2 mM. Mn competitively inhibits phase 2 zinc uptake: Mg acts as a ‘mixed-type’ inhibitor. Electron microscopy of unstained material indicates that part at least of phase 2 Zn is deposited in the cytoplasm and nucleus. A model for the metabolic uptake of Zn involving phase 1 binding as a requisite preliminary process is suggested.


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