The pigment of Xanthomonas populi is a nonbrominated aryl-heptaene belonging to xanthomonadin pigment group 11 [Canker disease of poplar trees (Populus spp.)]

Based on mass spectrometry and electronic absorption spectroscopy, the main pigment from X. populi (synonym: Aplanobacter populi ) was identified as a nonbrominated aryl-heptaene. The X. populi pigment was indistinguishable -- on the basis of cochromatography and electronic absorption spectroscopy -- from an authentic sample of a xanthomonadin belonging to Pigment Group 11, previously found as minor components in strains belonging to the X. campestris taxospecies( specifically in the X. pruni and X. vesicatoria nomenspecies). Possession of a xanthomonadin pigment confirms the placement of X. populi in the genus Xanthomonas and this particular pigment serves to distinguish X. populi from the five other taxospecies presently assigned to that genus. The Xanthomonas sp. isolated from Salix , which purportedly "shows affinities to" X. populi , forms a monobrominated aryl-polyene pigment and -- on that basis -- in unlike X. populi .