Xanthomonadales | |
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Scientific classification | |
Kingdom: | Bacteria |
Phylum: | Proteobacteria |
Class: | Gammaproteobacteria |
Families | |
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Synonyms | |
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The Xanthomonadales are a bacterial order within the Gammaproteobacteria. They are one of the largest groups of bacterial phytopathogens, harbouring species such as Xanthomonas citri, Xanthomonas euvesicatoria, Xanthomonas oryzae and Xylella fastidiosa. These bacteria affect agriculturally important plants including tomatoes, bananas, citrus plants, rice, and coffee. Many species within the order are also human pathogens. Species within the Stenotrophomonas genus are multidrug resistant opportunistic pathogens that are responsible for nosocomial infections in immunodeficient patients.
The Xanthomonadales are gram-negative, catalase positive, non-spore forming obligate aerobes. Members belonging to the order are straight rods lacking prosthecae. While some members are non-motile, other species within the order are motile by means of flagella. Stenotrophomonas is the only genus capable of nitrate reduction within the Xanthomonadales.
The Xanthomonadales consist of 28 validly named genera among two families: Xanthomonadaceae and Rhodanobacteraceae. The Xanthomonadaceae consists of 13 genera while the Rhodanobacteraceae consist of 14 genera. The families can be distinguished from one another on the basis of conserved signature indels found among a variety of proteins, specific for each family. These indels are in parallel with phylogenomic analysis that reveal two distinct clades that appear to be evolutionarily divergent. Lysobacterales and Lysobacteraceae are earlier synonyms of Xanthomonadales and Xanthomonadaceae, respectively.