Published online by Cambridge University Press: 14 April 2009
This report describes the existence of a mutation in a proA1 pabaA6 yA2 strain of Aspergillus nidulans, which prevents it growing on elevated concentrations of nitrite. The nitrite toxicity marker (nihA) resulted from a mutation in a single gene representing a new locus in linkage group I, and behaved as a recessive character. The observed recombination frequencies between nihA and proA1 and between nihA and pabaA6 were about 1 and 11%, respectively. Nitrite toxicity was not due to a defect in nitrite reductase, because the mutant grew well on nitrate. Furthermore, ammonium protected both nis-5 and niiA− strains against nitrite toxicity, which was not observed for the nihA strain. Since growth of the mutant was inhibited more by a mixture of ammonium and nitrite, compared to nitrite alone, it is proposed that the proA1 pabaA6 yA2 strain has a mutation leading to increased efficiency in nitrite uptake, which is not repressed by ammonium.