The extremely acid resistant filamentous fungus Bispora sp. (possessing two distinct growth optima at pH 1 and pH 7) is able to utilize metal complexed cyanides as N-source and to grow with acetamide as the only nitrogen and carbon source at both pH 1. 0 and 7. 0, whereas little growth is observed with formam ide as N-source. The nitrogen content of the fungus grown with acetamide is similar tp 'that of the control grown with NH4+ as N-source but higher than those cultures deprived of nitrogen. In the absence of appropriate substrates the fungus did not express amidases such, as urease, formamidase, acetamidase, whereas in the presence of formam ide and acetamide, formamidase activity, but no acetamidase activity was observed. Since the fungus is able to grow with acetamide as the only C- and N-source, data imply the involvement of an enzyme in acetamide metabolism which is different from a normal acetamidase. The incorporation of 14C-acetamide into the fungus and the subsequent utilization of the substrate, as analyzed by TLC, support the view that inducible enzymes related to C1-metabolism are of importance for the nutrition of Bispora sp. grown at pH 1.0 with acetamide as C- and N-source.