Azonexus caeni is a species of nitrogen-fixing bacteria.[1] It is a root bacteria and together with Azonexus fungiphilus and Azonexus hydrophilus is one of the three species in the genus. It is Gram-negative, motile, non-spore-forming and slightly curved rod-shaped. Slu-05T (=DSM 17719T=KCTC 12530T=CCBAU 10199T) is the type strain.