GENETIC-ANALYSIS OF BENZOATE METABOLISM IN ASPERGILLUS-NIGER

The benzoate metabolism of Aspergillus niger was studied as part of a design to clone the benzoate-4-hydroxylase gene of this fungus on the basis of complementation. Filtration enrichment techniques yielded mutants defective for different steps of benzoate degradation: bph (benzoate-4-hydroxylase), phh (4-hydroxybenzoate-3-hydroxylase) and prc (protocatechuate ring cleavage) mutants. In this way the degradation pathway for benzoate, involving the formation of 4-hydroxybenzoate and 3,4-dihydroxybenzoate has been confirmed. In addition a mutant sensitive to benzoate has been found. Complementation tests in somatic diploids showed that the bph mutants belonged to two complementation groups. The major group is probably defective in the structural gene (bphA). All phh mutants tested belonged to one complementation group. The prc mutants could be divided into several groups on the basis of their growth on different aromatic substrates and on the basis of the complementation test. The phh and both bph mutations are shown to be located on different chromosomes. © 1990 Springer-Verlag.