Chlorate Resistance and Nitrate Assimilation in Industrial Strains of Penicillium chrysogenum

Several chlorate-resistant mutants of Penicillium chrysogenum were isolated and analysed; all were affected in nitrate assimilation. Nine loci were recognized by complementation analysis and these appear to be equivalent to the niaD (nitrate reductase structural gene), nirA (control locus) and seven cnx loci (responsible for the biosynthesis of a cofactor for nitrate reductase) of Aspergillus nidulans. The organization of the nitrate assimilation genes appears to be similar in both organisms, even to the extent of having contiguous genes coding for the nitrate and nitrite reductase enzymes.