A Specific Transport System for Manganese in the Filamentous Fungus Aspergillus niger

SUMMARY: The existence of energy-dependent Mn2+ influx in Aspergillus niger ATCC 11414 was demonstrated both with mycelia grown for production of citric acid and in resting mycelia suspended in ‘Good’-buffers. A specific high-affinity transport system was detected at submicromolar concentrations of 54Mn2+ which functioned independently of the transport of Mg2+ and Ca2+, but was preferentially inhibited by Zn2+, Cu2+, Cd2+. The rate of Mn2+ transport was suboptimal in the citric acid production medium (pH 3.8 or lower) as the pH optimum was found to be 5.6 in the buffer experiments.