Xanthomonas is a genus of the Pseudomonaceae family. All organisms in this genus are
plant pathogens. The Xanthomonas pathovars infect a large selection of plants including some
of agricultural interest, e.g. cabbage, alfalfa, and beans.
Xanthomonas cells occur as single straight rods, 0.4±0.7 mm wide and 0.7±1.8 mm
long (Fig. 3). The cells are motile, Gram-negative, and they have a single polar flagellum
(1.7±3 mm long) (Fig. 3). The microorganism is chemiorganotrophic and an obligate
aerobe with a strictly respiratory type of metabolism that requires oxygen as the terminal
electron acceptor. The bacterium cannot denitrify, and it is catalase-positive and oxidasenegative.
The colonies are usually yellow, smooth, and viscid (Bradbury, 1984). Xanthomonas
sp. are able to oxidize glucose and the Entner±Doudoroff pathway is predomi