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The potato psyllid, Bactericera cockerelli, feeds on a potato and infects it with "Candidatus Liberibacter solanacearum", the bacterium that causes zebra chip disease.
Scientific classification

Fagen et al. 2014[1]

See text.


"Candidatus Liberibacter" Jagoueix et al. 1997

Liberibacter is a genus of Gram-negative bacteria in the Rhizobiaceae family. Detection of the liberibacteria is based on PCR amplification of their 16S rRNA gene with specific primers. Members of the genus are plant pathogens mostly transmitted by psyllids. The genus was originally spelled Liberobacter.[2]

Most importantly, Liberibacter is a causative agent of Huanglongbing disease (HLB) also known as citrus greening disease.[3] Liberibacter is transmitted by two insects from Psyllidae family – Diaphorina citri in Asia, Brazil and Florida, and Trioza erytreae in Africa. The Asian HLB strain, "Candidatus Liberibacter asiaticus" is more heat tolerant, while the African strain, Candidatus Liberibacter africanus is asymptomatic at temperatures above 30 °C.[3] Species of Liberibacter, infecting solanaceous plants has been identified and it was carried by another psyllid, a potato pest Bactericera cockerelli.[3][4]


The genetic diversity within the genus is best expressed as the diversity across genomes. More than 60 genomes have been sequenced, ranging in size from 233 kb to about 1.5 MB, hence the genomes are small compared to most other bacteria. The smallest genome (Candidatus Liberibacter asiaticus strain SGCA1) encodes only 655 proteins, while the largest genome (Candidatus Liberibacter asiaticus Tabriz. 3) encodes 2174 proteins.[5][6]

The small genome size is typical for pathogenic bacteria which often undergo genome reduction. This is due to adaptation to their host which often provides many nutrients, so that the parasite does not need genes to produce those nutrients itself.[7]


Liberibacter bacteria are carried in the hemolymph and salivary glands of psyllids. Since psyllids feed on sap, this provides bacteria the entry to phloem of the plant.[3] They induce significant metabolic and regulatory changes that damage the plants transport system and affects plants defense systems. These impairments have downstream negative effects on citrus microbiome of the infected plants.[8]

Since Liberibacter cannot be cultivated outside of its vector or host, genetics, bacteria-vector and bacteria-plant interaction have not yet been thoroughly explored. Factors important for adaption and colonization or possible coevolution are not yet understood.[3][8] Liberibacter activates salicylic acid pathway in host, likely due to recognition of extracellular molecules such as lipopolyscacharides or flagella. Pathogen in turn likely mitigates the effects, because it encodes SA hydroxylase, that degrades salicylic acid. Liberibacteria were shown to affect the spread of vector, by influencing the flight frequencies and sexual attraction of D. citri. On the other hand, infection with Liberibacter causes higher mortality of D. citri adults, but not nymphs.[8] Liberibacter is a part of the psyllid microbiota and co-existence with other bacteria likely has impact on the overall fitness of the insect, as well as outcome of the disease.[8]


Primary strategy for HLB disease management is a vector control. Antimicrobial treatment can suppress Liberibacter species, however usage of broad spectrum antibiotics is inadvisable due to adverse environmental effects. Alternative treatments, such as heat therapy, i.e., incubation of plant at temperatures above 40 °C for several days, show varying effects. Another suggested alternatives include the use of compounds that alleviate disease symptoms and boost plants defense systems or reinforcing natural citrus microbiota in order to compete with Liberibacter species.[9] [10] Early detection of HLB positive trees and removal from the groves, and extensive control of psyllids are the crucial HLB management strategies.[11][12]


Named species include:[13]


  1. ^ Fagen JR, Leonard MT, Coyle JF, McCullough CM, Davis-Richardson AG, Davis MJ, Triplett EW (2014). "Liberibacter crescens gen. nov., sp. nov., the first cultured member of the genus Liberibacter". Int J Syst Evol Microbiol. 64 (7): 2461–2466. doi:10.1099/ijs.0.063255-0. PMID 24786353.
  2. ^ Taxonomy browser
  3. ^ a b c d e Nadarasah G, Stavrinides J (May 2011). "Insects as alternative hosts for phytopathogenic bacteria". FEMS Microbiology Reviews. 35 (3): 555–75. doi:10.1111/j.1574-6976.2011.00264.x. PMID 21251027.
  4. ^ a b Hansen AK, Trumble JT, Stouthamer R, Paine TD (September 2008). "A new Huanglongbing Species, "Candidatus Liberibacter psyllaurous," found to infect tomato and potato, is vectored by the psyllid Bactericera cockerelli (Sulc)". Applied and Environmental Microbiology. 74 (18): 5862–5. Bibcode:2008ApEnM..74.5862H. doi:10.1128/AEM.01268-08. PMC 2547047. PMID 18676707.
  5. ^ "Genome List". Retrieved 2023-07-31.
  6. ^ "MAG: Candidatus Liberibacter asiaticus isolate Tabriz.3, whole genome shotgun sequencing project". 2022-02-19. {{cite journal}}: Cite journal requires |journal= (help)
  7. ^ Koskiniemi, Sanna; Sun, Song; Berg, Otto G.; Andersson, Dan I. (June 2012). "Selection-driven gene loss in bacteria". PLOS Genetics. 8 (6): e1002787. doi:10.1371/journal.pgen.1002787. ISSN 1553-7404. PMC 3386194. PMID 22761588.
  8. ^ a b c d Wang N, Stelinski LL, Pelz-Stelinski KS, Graham JH, Zhang Y (April 2017). "Tale of the Huanglongbing Disease Pyramid in the Context of the Citrus Microbiome". Phytopathology. 107 (4): 380–387. doi:10.1094/PHYTO-12-16-0426-RVW. PMID 28095208.
  9. ^ Blaustein RA, Lorca GL, Teplitski M (April 2018). "Challenges for Managing "Candidatus Liberibacter" spp. (Huanglongbing Disease Pathogen): Current Control Measures and Future Directions". Phytopathology. 108 (4): 424–435. doi:10.1094/PHYTO-07-17-0260-RVW. PMID 28990481.
  10. ^
  11. ^ Pandey, Sheo Shankar; Wang, Nian (June 2019). "Targeted Early Detection of Citrus Huanglongbing Causal Agent ' Candidatus Liberibacter asiaticus' Before Symptom Expression". Phytopathology. 109 (6): 952–959. doi:10.1094/PHYTO-11-18-0432-R. PMID 30667340.
  12. ^ Wang, Nian (May 2019). "The Citrus Huanglongbing Crisis and Potential Solutions". Molecular Plant. 12 (5): 607–609. doi:10.1016/j.molp.2019.03.008. PMID 30947021.
  13. ^ "Liberibacter". UniProt Consortium.
  14. ^ "Trioza erytreae" (PDF). European and Mediterranean Plant Protection Organization (EPPO) quarantine pest. Archived from the original (PDF) on 2010-07-13.
  15. ^ Teixeira Ddo C, Saillard C, Eveillard S, Danet JL, da Costa PI, Ayres AJ, Bové J (September 2005). ""Candidatus Liberibacter americanus", associated with citrus huanglongbing (greening disease) in São Paulo State, Brazil". International Journal of Systematic and Evolutionary Microbiology. 55 (5): 1857–62. doi:10.1099/ijs.0.63677-0. PMID 16166678.
  16. ^ "Asian citrus psyllid". Featured Creatures.
  17. ^ Morris J, Shiller J, Mann R, Smith G, Yen A, Rodoni B (July 2017). "Novel "Candidatus Liberibacter" species identified in the Australian eggplant psyllid, Acizzia solanicola". Microbial Biotechnology. 10 (4): 833–844. doi:10.1111/1751-7915.12707. PMC 5481521. PMID 28387006.
  18. ^ Complete genome sequence of Liberibacter crescens BT-1
  19. ^ Raddadi N, Gonella E, Camerota C, Pizzinat A, Tedeschi R, Crotti E, Mandrioli M, Bianco PA, Daffonchio D, Alma A (February 2011). ""Candidatus Liberibacter europaeus" sp. nov. that is associated with and transmitted by the psyllid Cacopsylla pyri apparently behaves as an endophyte rather than a pathogen". Environmental Microbiology. 13 (2): 414–26. doi:10.1111/j.1462-2920.2010.02347.x. hdl:2318/133454. PMID 21040355. S2CID 20625405.
  20. ^ Liefting LW, Weir BS, Pennycook SR, Clover GR (September 2009). "'Candidatus Liberibacter solanacearum', associated with plants in the family Solanaceae". International Journal of Systematic and Evolutionary Microbiology. 59 (Pt 9): 2274–6. doi:10.1099/ijs.0.007377-0. PMID 19620372.
  21. ^ Nelson WR, Sengoda VG, Alfaro-Fernandez AO, Font MI, Crosslin JM, Munyaneza JE (2012). "A new haplotype of "Candidatus Liberibacter solanacearum" identified in the Mediterranean region". European Journal of Plant Pathology. 135 (4): 633–639. doi:10.1007/s10658-012-0121-3. S2CID 10654496.
  22. ^ Teresani GR, Bertolini E, Alfaro-Fernández A, Martínez C, Tanaka FA, Kitajima EW, Roselló M, Sanjuán S, Ferrándiz JC, López MM, Cambra M, Font MI (August 2014). "Association of "Candidatus Liberibacter solanacearum" with a vegetative disorder of celery in Spain and development of a real-time PCR method for its detection". Phytopathology. 104 (8): 804–11. doi:10.1094/PHYTO-07-13-0182-R. hdl:10251/82656. PMID 24502203.
  23. ^ Sumner-Kalkun, Jason C.; Highet, Fiona; Arnsdorf, Yvonne M.; Back, Emma; Carnegie, Mairi; Madden, Siobhán; Carboni, Silvia; Billaud, William; Lawrence, Zoë; Kenyon, David (2020-10-06). "'Candidatus Liberibacter solanacearum' distribution and diversity in Scotland and the characterisation of novel haplotypes from Craspedolepta spp. (Psylloidea: Aphalaridae)". Scientific Reports. 10 (1): 16567. doi:10.1038/s41598-020-73382-9. ISSN 2045-2322. PMC 7538894.
  24. ^ Crosslin, James M.; Munyaneza, Joseph E. (2009). "Evidence that the Zebra Chip Disease and the Putative Causal Agent Can be Maintained in Potatoes by Grafting and in Vitro". American Journal of Potato Research. 86 (3): 183–187. doi:10.1007/s12230-009-9070-6. S2CID 32565774.
  25. ^ Sumner-Kalkun, Jason C.; Highet, Fiona; Arnsdorf, Yvonne M.; Back, Emma; Carnegie, Mairi; Madden, Siobhán; Carboni, Silvia; Billaud, William; Lawrence, Zoë; Kenyon, David (2020-10-06). "'Candidatus Liberibacter solanacearum' distribution and diversity in Scotland and the characterisation of novel haplotypes from Craspedolepta spp. (Psylloidea: Aphalaridae)". Scientific Reports. 10 (1): 16567. doi:10.1038/s41598-020-73382-9. ISSN 2045-2322. PMC 7538894.
  26. ^ Nelson WR, Fisher TW, Munyaneza JE (2011). "Haplotypes of "Candidatus Liberibacter solanacearum" suggest long-standing separation". European Journal of Plant Pathology. 130: 5–12. doi:10.1007/s10658-010-9737-3. S2CID 21470208.
  27. ^ Casteel CL, Hansen AK, Walling LL, Paine TD (2012). "Manipulation of plant defense responses by the tomato psyllid (Bactericerca cockerelli) and its associated endosymbiont "Candidatus Liberibacter psyllaurous"". PLOS ONE. 7 (4): e35191. Bibcode:2012PLoSO...735191C. doi:10.1371/journal.pone.0035191. PMC 3335145. PMID 22539959.

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