Characterization of an Azospirillum brasilense Tn5 mutant with enhanced N-2 fixation: the effect of ORF280 on nifH expression

Disruption of an open reading frame (ORF) of 840 bp (280 amino acids; ORF28 0) in an Azospirillum brasilense Tn5 mutant resulted in a pleiotrophic phen otype. Besides an enhanced N-2-fixing capacity and altered expression patte rn of a nifH-gusA fusion, growth on the charged polar amino acids glutamate and arginine was severely affected. ORF280, similar to previously identifi ed ORFs present in Bradyrhizobium japonicum (ORF277), Paracoccus denitrific ans (ORF278) and Rhodobacter capsulatus (ORF277), exhibits in its C-terminu s a significant similarity with the recently defined Family of universal st ress proteins. (C) 2000 Federation of European Microbiological Societies. P ublished by Elsevier Science B.V. All rights reserved.