For the ornithine fermentation pathway, described more than 70 years ago, genetic and biochemical information are still incomplete. We present here the experimental identification of the last four missing genes of this metabolic pathway. They encode L-ornithine racemase, (2R,4S)-2,4-diaminopentanoate dehydrogenase, and the two subunits of 2-amino-4-ketopentanoate thiolase. While described only for the Clostridiaceae to date, this pathway is shown to be more widespread.