Xanthomonas

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A Microbial Biorealm page on the genus Xanthomonas

Xanthomonas campestris, the causative agent of many plant diseases. From the Center for Integrated Plant Systems.

Classification

Higher order taxa:

Bacteria; Proteobacteria; Gammaproteobacteria; Xanthomonadales; Xanthomonadaceae

Species:

Pseudomonas cissicola, X. albilineans, X. arboricola sp., X. axonopodis sp., X. bromi, X. campestris spp., X. cassavae, X. citri, X. codiaei, X. cucurbitae, X. cynarae, X. fragariae, X. gardneri, X. hortorum, X. hyacinthi, X. melonis, X. oryzae sp. , X. pisi, X. populi, X. sacchari, X. theicola, X. translucens sp., X. vasicola, X. vesicatoria, X. spp.

NCBI: Taxonomy Genome: Xanthomonas axonopodis Xanthomonas campestris

Description and Significance

Xanthomonas is a Gram-negative rod-shaped bacteria known for being a common plant pathogen.

Genome Structure

The genome of a Xanthomonas bacterium consists of a circular chromosome of about five megabases. Each cell also contains two plasmids, of length 34 kb and 65 kb, respectively. There is considerable colinearity between the genomes of X. axonopodis and X. campestris, suggesting that only three major rearrangement events have occurred in the time separating them (BioMed, 2002).

Cell Structure and Metabolism

A blood culture of Xanthomonas maltiphilia. From Buddycom.

Xanthomonas is a flagellated, rod-shaped cell, which allows the bacterium to move throughout an infected plant. Xanthomonas is dependent on the type III protein secretion system, which relies on transport proteins, secreting several hypersensitive reaction proteins and outer proteins, causing an interaction with the plant (D.Büttner et al., 2002)

Ecology

Xanthomonas bacteria grow almost exclusively in plants. In São Paulo, Brazil, the numbers of citrus tress with citrus canker from Xanthomonas have grown at an astonishing rate. This has given the Brazilians no choice but to destroy not only the diseased trees, but trees within a 30m radius of the contaminated tree, putting the number of destroyed trees over 500,000 in 1998 alone (The Genome Project, 2004).

Pathology

Xanthomonas fragariae affects strawberry plants, causing undesirable lesions on the fruit, making it unmarketable. From the University of Florida.

Xanthomonas affects many types of hosts, including citrus, beans, grapes, cotton, and rice. X. axonopodis causes citrus cankers and black rot, which affects many commercial plants. Typical symptoms of the disease include lesions on the leaves, fruit, and stems as well as twig dieback (Cancer Annotation Project, 2002).

Disease caused by Xanthomonas bacteria. From the University of Connecticut.

Symptoms of citrus canker, including small yellow lesions, can begin to appear as soon as only one week after the initial infection up to two months afterwards. Eventually, the initial yellow lesions turn brown and form a 'corky' surface, providing a method for later transmission to other plants and tissues (Genome Project, 2004).

References

General:

• Buddycom. 2004. Bacteria, gram negative bacilli.
• The Center for Integrated Plant Systems. 23 Nov 1998. Biological Control Program. Pathogens: Vargas.
• Büttner, D., D. Nennstiel, B. Klüsener, and U. Bonas. Institut für Genetik. 3 Feb 2002. Functional Analysis of HrpF, a Putative Type III Translocon Protein from Xanthomonas campestris pv. vesicatoria.
• The Genome Project. 2004. Xanthomomnas axonopodis.

Genome:

• BioMed Central. The Scientist. 28 May 2002. Comparing Xanthomonas.

Ecology:

• The Genome Project. 2004. Xanthomomnas axonopodis.

Pathology:

• Cancer Annotation Project. 16 Jul 2002. About Xanthomonas.
• The Genome Project. 2004. Xanthomomnas axonopodis.
• Tomato Diseases
• The University of Florida. 2000. Colletotrichum diseases of strawberry in Florida.