roseicyclus roseicyclus in taxonomy, roseicyclus is a genus of the rhodobacteraceae. roseicyclus scientific classification domain: bacteria phylum: pseudomonadota class: alphaproteobacteria order: rhodobacterales family: rhodobacteraceae genus: roseicyclus species roseicyclus mahoneyensis synonyms roseicyclus rathgeber et al. 2005