Xanthomonadaceae

Xanthomonadaceae is a family of Gram-negative, non-spore-forming bacteria within the order Xanthomonadales of the class Gammaproteobacteria. Members are metabolically diverse and occur in a range of habitats, including soil, water, plant surfaces, and diseased plant tissues. Most species are rod-shaped and aerobic; many produce a yellow-orange pigment called xanthomonadin, a characteristic associated with several but not all genera in the family.

The taxonomy places Xanthomonadaceae in the Gammaproteobacteria; its genera include Xanthomonas, Xylella, Stenotrophomonas, Pseudoxanthomonas, and related lineages. The best known members are plant-associated bacteria; the genus Xanthomonas contains numerous phytopathogens that cause diseases such as citrus canker, bacterial spot, and leaf streak in various crops. Xylella fastidiosa, another member, causes vascular diseases in grapevines, olive trees, and other hosts and is transmitted by xylem-feeding insects. In contrast, Stenotrophomonas and Pseudoxanthomonas include environmental species and opportunistic human pathogens, notably Stenotrophomonas maltophilia, which can cause infections in hospitalized or immunocompromised individuals.

Physiological tests vary among species, but members are generally non-spore-forming and may be oxidase-positive or -negative and catalase-positive. The family is of interest for agriculture due to plant pathogens and for medicine because of environmental and opportunistic infections. Ongoing taxonomic revision and genomic analyses continue to refine the boundaries and relationships within Xanthomonadaceae.