Xanthomonas campestris

Xanthomonas campestris is a gram-negative, obligate aerobic bacterium that is a member of the Xanthomonas genus, which is a group of bacteria that are commonly known for their association with plant disease. The species is considered to be dominant amongst its genus, as it originally had over 140 identified pathovars and has been found to infect both monocotyledonous and dicotyledonous plants of economical value with various plant diseases. This includes "black rot" in cruciferous vegetables, bacterial wilt of turfgrass, bacterial blight, and leaf spot, for example. These bacteria are facultative saprophytes, meaning that they are typically parasitic while also having the ability to live on dead or decaying organic matter under the proper conditions. Upon initial infection, the bacteria remain in the epiphytic stage; however, the harmful endophytic stage is reached when the bacteria actually enter the plant host through natural openings. In general, the genes that contribute significantly to the plant-bacteria relationship are the avirulence (avr) genes, the hypersensitivity response and pathogenicity (hrp) genes, and the pathogenicity factors (rpf) genes. Additionally, the virulence determinants associated with the seedborne diseases that result from this bacterium include extracellular enzymes, polysaccharides, lipopolysaccharides, etc. Several strains of Xanthomonas campestris also produce an exopolysaccharide called xanthan, making it valuable in the commercial production of xanthan gum, which has important uses in the food, oil, agricultural, and pharmaceutical industries. There have been over 140 pathovars of Xanthomonas campestris that have been identified, and they are typically named according to the plant that they were first found to infect. However, upon further investigation of genetic relationships, many of these pathovars are now being reclassified as different species within the Xanthomonas genus instead. This leaves six pathovars of Xanthomonas campestris remaining, which includes Xanthomonas campestris pv.