The utilization of aliphatic amides and their metabolism in the facultatively chemolithotrophic hydrogen bacterium has been investigated. This strain grew on fructose with formamide or acetamide as nitrogen sources, and these substrates induced formamidase. Ammonia repressed formamidase formation. Propionamide, butyramide and valeramide served as carbon and nitrogen sources and induced a different amidase, valeramidase. This enzyme was highly active with valeramide and less active with shorter acylamides but did not hydrolyse formamide. Valeramidase was subject to catabolite repression by fructose and succinate. Mutants altered in the regulation of amidase formation were isolated. A mutant able to grow with formamide and acetamide as carbon source formed formamidase constitutively, and this enzyme could not be repressed by ammonia in this mutant; its growth on formamide was autotrophic. A mutant able to grow with acetamide but not with formamide as carbon source was semi-constitutive for valeramidase; in this mutant the inducer specificity was altered and acetamide was the most potent inducer of valeramidase.


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