Xanthomonas campestris

A Microbial Biorealm page on the genus Xanthomonas campestris

this page is still under construction.

Classification

Xanthomonas campestris' biofilm on plant surface
Courtesy of Fett & Cooke, ASM MicrobeLibrary [1]

Higher order taxa

[Kingdom] Bacteria

[Phylum] Proteobacteria

[Class] Gamma Proteobacteria

[Order] Xanthomonadales

[Family] Xanthomonadaceae

[Genus] Xanthomonas

[Species] Xanthomonas campestris

Species

NCBI: Taxonomy

Xanthomonas campestris

Description and significance

Xanthomonas campestris is an aerobic, Gram-negative rod known to cause the black rot in crucifers by darkening the vascular tissues. Host associated, over 20 different pathovars of X. campestris have been identified by their distinctive pathogenicity on a wide range of plants including crops and wild plants. This bacterium is mesophilic with optimal temperature at 25-30 degrees Celsius (77-85 degrees Fahrenheit). It is inactive at temperatures below 10 degrees Celsius (50 degrees Fahrenheit). [1] X. campestris have long pilus that helps them glide through water. They can live in a soil for over a year and spread through irrigation and surface water. Spraying healthy plants with copper fungicides may reduce the spread of the bacteria in the field. However, once the plant has been infected, X. campestris will eventually spread to the seed stalk inhibiting the growth of a healthy offspring.

By pure culture fermentation, X. campestris can produce an extracellular polysaccharide known as xanthan gum that is commercially manufactured as a stabilizing agent used in many industries. This organism is a model organism for plant pathogens in studying their interaction between hosts. Due to the deficit in crops, further study of X. campestris’ genome may provide a solution to make plants resistant to this pathogen.

Genome structure

X. campestris have circular chromosomes containing at least two plasmids. The genome structures of X. campestris contain variation depending on the pathovars. However, the different strains of X. campestris exhibit similar characteristics like the mobile genetic elements and protein coding sequences. In 2002, the complete genome of X. campestris pv campestris str. ATCC 33913 was completed containing over 5,076,188 nucleotides that encode for over 4200 protein codings and 61 structural RNAs. [15] In X. campestris pv. campestris (Xcc) wild-type strain B100, it is found to contain a plasmid which contains 3-4 kb of chromosomal fragments. [?? (2)] With over 548 unique coding sequences, X. campestris pv. Vesicatoria (Xcv) is composed of a 5.17-Mb circular chromosome, four plasmids, and an essential type III protein secretion system for pathogenicity [3]. Using Recominbase-based In Vivo Expression Technology to target tomato, Xcv has been found to have 61 genes that are involved in the interaction between pathogen and host including a necessary virulence transporter, citH homologue gene [4].

Cell structure and metabolism

X. campestris is a rod-shaped Gram-negative bacteria characterized by its two cell walls and yellow pigment. It has a filamentous structure of pili that provides motility in water, appendage to cell surface, and also a way to transfer bacterial proteins to the plant.

X. campestris is an aerobic bacterium that performs a number of metabolic pathways that are uniquely dependent on the pathovar. Entire genome sequencing of Xcv show carbohydrate metabolism that include: Glycolysis/ Gluconeogenesis, Citrate cycle (TCA cycle), Pentose phosphate pathway, and more. Xcv gains its energy source through oxidative phosphorylation, carbon fixation, methane, nitrogen, and sulfur metabolism [17].

X. campestris acquire carbon from the host to break it down and form glucose through Gluconeogenesis. Further research has shown that in gluconeogenesis, Xcc contain only the malic enzyme-PpsA route which is essential for virulence [15]. In addition, X. campestris contain a type III secretion system (TTSS) that is necessary in order to attack the host [5]. TTSS is important in pathogenesis because it delivers effector proteins into the host cell. These effectors may behave avirulently by disguising itself to secrete several hypersensitive reaction and outer proteins in order for interaction to occur with the host cells. [6] Creating biofilm on plant surfaces, X. campestris exemplifies cell-cell communication through diffusible signal factor (DSF). [7].

X. campestris possess the ability to ferment xanthan which is commerically produced and used in a variety of industries including food and oil companies.

Ecology

X. campestris causes great loss in agriculture due to their habitat in plants. It can live in the soil for over a year and spread through irrigation and surface water. X. campestris thrive particularly during wet and warm weathers with optimal temperatures at 25-30 degrees Celsius (77-85 degrees Fahrenheit) [1]. These microbes depend on water for survival and movement to the next host. Due to contamination during cultural operations, affected plants usually occur in the same rows when farmed [8]. See pathology for more details.

Pathology

Bacterial spot lesions on bellpepper fruit caused by X. campestris pv. vesicatoria (Xcv). Courtesy of David Ritchie. [2]

X. campestris can be spotted by the black lesions that develop on plant surfaces when infected. The pathogen first interacts with the host by secreting an array of effector proteins including hypersensitive reaction using type III secretion system (TTSS) [5]. TTSS is necessary for pathogenesis because it lower the plant’s defense. X. campestris then targets the vascular tissue causing darkening and marginal leaf chlorosis. [1] X. campestris seeps into the leaf towards the stomates, hydathodes at leaf margins, and to the epidermal cells causing new lesion. [8] Severe infection occurs in a young seedling. Since the disease advances throughout the plant, the main stem cannot form, stunting the growth and blackening the veins. Eventually, the bacterium proliferates throughout the vascular system and to the seed stalk causing the seed to become infected of future diseases [8].

X. campestris occurs more during the wet seasons because they possess pilus that helps them glide through wet leaves. Covering an affected area in numerous numbers, once a plant is infected, the pathogen will spread in any form of water movement including splashes of rain drop [8].

Virulence factors include lytic enzymes that attack the plant's cell wall, excretion of proteases, amylases, cellulases and lipases that help lower the plant’s defense mechanisms [9]. In addition, the Rpf gene cluster is also necessary for pathogenesis in order for X. campestris to regulate the production of these virulent factors. [14]

Application to Biotechnology

X. campestris is used to create a stabilizing agent called xanthan gum. It was first produced at Kelco Company, a major pharmaceutical company. This preservative is an ingredient in products like Kraft French dressing, Weight Watchers food, Wonder Bread products, and more. (11) Fermented from glucose by X. campestris, xanthan gum is used to extend freshness for food products. In addition, xanthan gum also prolongs oil and gas wells even after production. Either pumped into the ground or using high pressure sandblasting, mixing water and xanthan gum into the wells will help release crude products of oil and cut through rocks in gas and oil wells. Xanthan gum costs $7 per pound compared to cornstarch for 89 cents per pound. (11)

Current Research

8.1 Biological Control with strains of Bacillus

Genome sequence is being done in search of the essential genes needed in order to develop resistant plants. An experiment was done using Bacillus strains including B. cereus, B. lentimorbus, and B. pumilus as an antagonist for pathogen Xcc in cabbage. Evidence has shown some hope for biological control when the Bacillus strain was added in the roots [18].

8.2 Regulatory network for cell-cell communication

Recent students have shown X. campestris use the diffusible signal factor (DSF) for cell-cell communication. In order for microcolonies to form structured biofilm, synthesis of DSF is required from the regulation of pathogenicity factor (Rpf) cluster. The Rpf cluster is made up of necessary genes needed in order for pathogenesis to occur. Without the critical DSF signalling, Xcc will create an unstructured biofilm of bacteria. Further research is being conducted to understand how the regulatory network is being monitored [13].

8.3 Genetic Variation in wild crucifers

Current research is being done on the genetic diversity in Xcc of wild crucifers. With the most diverse and abundant wild cruciferous plants in the world, research was done in California to find any differences in genetic strains on Xcc in infected wild weeds. From both non-cultivated and cultivated areas, Xcc was isolated from different regions of California. Using Amplified fragment length polymorphism PCR (AFLP) to identify genetic variation in strains, over 72 strains were sequenced to show 7 unique genotypes that were limited to their respective sites. Non-cultivated wild weeds near the coast had strains of Xcc that were specific to the region and different from the weeds grown near produced crop areas. [12]

1.) Averre, Charles W. "Black Rot of Cabbage and Related Crops" Accessed on August 16, 2007. http://www.ces.ncsu.edu/depts/pp/notes/oldnotes/vg16.htm

2.) Ritchie David F, Averre Charles W. "Bacterial Spot of Pepper and Tomato". North Carolina State University College of Agriculture and Life Sciences. Accessed on August 20, 2007. http://www.ces.ncsu.edu/depts/pp/notes/Vegetable/vdin018/vdin018.htm

3.) Weber E, Ojanen-Reuhs T, Huguet E, Hause G, Romantschuk M, Korhonen TK, Bonas U, Koebnik R. "The type III-dependent Hrp pilus is required for productive interaction of ‘’Xanthomonas campestris pv. vesicatoria’’ with pepper host plants". ‘’Journal of Bacteriology.’’ 2005. Volume 187(7) p.2458-69. http://www.ncbi.nlm.nih.gov/sites/entrez?Db=pubmed&Cmd=ShowDetailView&TermToSearch=15774889&ordinalpos=1&itool=EntrezSystem2.PEntrez.Pubmed.Pubmed_ResultsPanel.Pubmed_RVAbstractPlus

4.) Kuntz, L. “X is for Xanthan Gum”. Food Product Design. Accessed on August 26, 2007. http://www.foodproductdesign.com/articles/761ingredient.html?cntwelcome=1

5.) Vorhölter FJ, Thias T, Meyer F, Bekel T, Kaiser O, Pühler A, Niehaus K. "Comparison of two ‘’Xanthomonas campestris pv. campestris’’ genomes revealed differences in their gene composition". ‘’Journal Biotechnology.’’ 2003. Volume 106(203). p.193-202. http://www.ncbi.nlm.nih.gov/sites/entrez?cmd=Retrieve&db=PubMed&list_uids=14651861&dopt=AbstractPlus

6.) “’’Xanthomonas campestris pv. campestris’’ str. ATCC 33913, complete genome”. ‘’Public Library of Science Biology.’’ 2002. Accessed on August 25, 2007. http://www.ncbi.nlm.nih.gov/sites/entrez?db=genome&cmd=Retrieve&dopt=Overview&list_uids=240

7.) Thieme F, Koebnik R, Bekel T, Berger C, Boch J, Büttner D, Caldana C, Gaigalat L, Goesmann A, Kay S, Kirchner O, Lanz C, Linke B, McHardy AC, Meyer F, Mittenhuber G, Nies DH, Niesbach-Klösgen U, Patschkowski T, Rückert C, Rupp O, Schneiker S, Schuster SC, Vorhölter FJ, Weber E, Pühler A, Bonas U, Bartels D, Kaiser O. "Insights into genome plasticity and pathogenicity of the plant pathogenic bacterium ‘’Xanthomonas campestris pv. vesicatoria’’ revleaed by the complete genome sequence". ‘’Journal of Bacteriology.’’ 2005. Volume 187(21). p 7254-66. http://www.ncbi.nlm.nih.gov/sites/entrez?cmd=Retrieve&db=pubmed&list_uids=16237009

8.) Tamir Ariel D., Navon N, Burdman S. "Identification of ‘’Xanthomonas campestris pv. vesicatoria’’ genes induced in its interaction with tomato". ‘’Journal of Bacteriology.’’ 2007. Volume 189(17). P.6359-71. http://www.ncbi.nlm.nih.gov/sites/entrez?Db=pubmed&Cmd=ShowDetailView&TermToSearch=17573477&ordinalpos=11&itool=EntrezSystem2.PEntrez.Pubmed.Pubmed_ResultsPanel.Pubmed_RVDocSum

9.) Weber E, Koebnik R. "Domain structure of HrpE, the Hrp pilus subunit of ‘’Xanthomonas campestris pv. vesicatoria’’". ‘’Journal of Bacteriology.’’ 2005. Volume 187(17). p. 6175-86. http://www.ncbi.nlm.nih.gov/sites/entrez?cmd=retrieve&db=pubmed&list_uids=16109959&dopt=AbstractPlus

10.) "’’Xanthomonas campestris pv. vesicatoria.’’" Kyoto Encyclopedia of Genes and Genomes. Accessed on August 24, 2007. http://www.genome.jp/kegg-bin/show_organism?menu_type=pathway_maps&org=xcv

11.) Tang DJ, He YQ, Feng JX, He BR, Jiang BL, Lu GT, Chen B, Tang JL. "‘’Xanthomonas campestris pv. campestris‘’ posesses a single gluconeogenic pathway that is required for virulence." ‘’Journal of Bacteriology.’’ 2005. Volume 187(17). p 6231-7. http://www.ncbi.nlm.nih.gov/sites/entrez?cmd=retrieve&db=pubmed&list_uids=16109965&dopt=AbstractPlus

12.) Torres PS, Malamud F, Rigano LA, Russo DM, Marano MR, Castagnaro AP, Zorreguieta A, Bouarab K, Dow JM, Vojnov AA. "Controlled synthesis of the DSF cell-cell signal is required for biofilm formation and virulence in ‘’Xanthomonas campestris." ‘’Environmental Microbiology.‘’ 2007. Volume 9(8). p. 2101-9. http://www.ncbi.nlm.nih.gov/sites/entrez?Db=pubmed&Cmd=ShowDetailView&TermToSearch=17635553&ordinalpos=1&itool=EntrezSystem2.PEntrez.Pubmed.Pubmed_ResultsPanel.Pubmed_RVDocSum

13.) Wang L, Tang X, He C. "The bifunctional effector AvrXccC of ‘’Xanthomonas campestris pv. campestris‘’ requires plasma membrane-anchoring for host recognition." ‘’Molecular Plant Pathology.’’ 2007. Volume 8(4). p 491–501. http://www.blackwell-synergy.com/doi/abs/10.1111/j.1364-3703.2007.00409.x?prevSearch=allfield%3A%28xanthomonas+campestris%29

14.) Niehaus Karsten. "The ‘’Xanthomonas campestris pv. campestris‘’ genome project." Accessed on August 20, 2007. https://www.genetik.uni-bielefeld.de/GenoMik/partner/bi_niehaus.html

15.) Dow JM, Crossman L, Findlay K, He YQ, Feng JX, Tang JL. "Biofilm dispersal in ‘’Xanthomonas campestris‘’ is controlled by cell-cell signaling and is required for full virulence to plants". ‘’Proceedings of the National Academy of Sciences of the United States of America.’’ 2003 September 16. Volume 100(19). p 10995-1000. http://www.ncbi.nlm.nih.gov/sites/entrez?cmd=retrieve&db=pubmed&list_uids=12960398&dopt=AbstractPlus

16.) "Technologies in the Marketplace." United States Department of Agriculture, Agricultural Research Service (ARS). Accessed on August 21, 2007. http://www.ars.usda.gov/business/docs.htm?docid=769&page=5

17.) Massomo S, Mortensen C, Mabagala R, Newman M, Hockenhull J. "Biological control of black rot (’’Xanthomonas campestris pv. campestris’’) of Cabbage in Tanzania with ’’Bacillus strains"’’. ’’Journal of Phytopathology. ’’ 2004. Volume 152(2). p. 98-105. http://www.blackwell-synergy.com/doi/abs/10.1111/j.1439-0434.2003.00808.x?prevSearch=allfield%3A%28xanthomonas+campestris%29

18.) Torres PS, Malamud F, Rigano LA, Russo DM, Marano MR, Castagnaro AP, Zorreguieta A, Bouarab K, Dow JM, Vojnov AA. "Controlled synthesis of the DSF cell-cell signal is required for biofilm formation and virulence in ’’Xanthomonas campestris"’’. ’’Environmental microbiology.’’ 2007. Volume 9(8). p 2101-9. http://www.ncbi.nlm.nih.gov/sites/entrez?Db=pubmed&Cmd=ShowDetailView&TermToSearch=17635553&ordinalpos=1&itool=EntrezSystem2.PEntrez.Pubmed.Pubmed_ResultsPanel.Pubmed_RVDocSum

19.) Ignatov, A., Sechler, A.J., Schuenzel, E., Agarkova, I.V., Vidaver, A.K., Oliver, B., Schaad, N.W. 2007. "Genetic diversity in populations of ’’Xanthomonas campestris pv. campestris’’ in cruciferous weeds in central coastal California". ’’Phytopathology. ’ 2007. Volume 97. p. 803-812. http://www.ars.usda.gov/research/publications/publications.htm?seq_no_115=201768