Mechanism of nickel resistance in a cobalt-resistant wall-less mutant of Neurospora crassa (fz; sg; os-1).

A cobalt-re sistant wall-less mutant of N. crassa (Cor-sl) characterized previously was also found to be 3-fold more resistant to nickel when compared to the parent wall-less mutant (W-sl). The Cor-si strain accumulates relati ve ly lower amounts of nickel when compared to W-sl. Sub-cellular fra cti onation showed signifi cant quantities of nickel to be associ ated with nuclear and mitochondrial fractions in both the wall-less mutants. However significant differences were observed in vacuolar fractions of W-sl and Cor-si strain s. Fractionation of cell-free extracts on .S ephadex G-10 column resolved nickel into two peaks, of which th e peak II in Cor- si constituted 70% of nickel , while the same in W -sl was about 30%. A 3-fold increase in hi stidine content was observed in case of Cor-si as compared to W-sl strain , suggesting its role in Ni-resistance.