Abstract
A region of the genome of Rhodobacter capsulatus has been sequenced and shown to encode proteins homologous to the NDI subunit and the 23 kDa subunit of the mitochondrial NADH:CoQ oxidoreductase (Complex I). The association of these two open reading frames in the R. capsulatus genome parallels the organisation of the chloroplast genome. It suggests that genes encoding subunits of the NADH:CoQ oxidoreductase must be clustered in the genome or R. capsulatus.