Nucleotide sequence of the rpoN (hno) gene region of Alcaligenes eutrophus: evidence for a conserved gene cluster.

The nucleotide sequence of the rpoN gene, formerly designated hno, and flanking DNA regions of the aerobic hydrogen bacterium Alcaligenes eutrophus has been determined; rpoN codes for the RNA polymerase sigma factor sigma 54 involved in nitrogen regulation and diverse physiological functions of gram-negative bacteria. In A. eutrophus hydrogen metabolism is under control of rpoN. The Tn5-Mob insertion in a previously isolated pleiotropic mutant was mapped within the rpoN gene. The derived amino acid sequence of the A. eutrophus RpoN protein shows extensive homology to the RpoN proteins of other organisms. Sequencing revealed four other open reading frames: one upstream (ORF280) and three downstream (ORF130, ORF99 and ORF greater than 54) of the rpoN gene. A similar arrangement of homologous ORFs is found in the rpoN regions of other bacteria and is indicative of a conserved gene cluster.