Liberibacter | |
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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 | |
Domain: | |
Phylum: | |
Class: | |
Order: | |
Family: | |
Genus: | Liberibacter Fagen et al. 2014
[1]
|
Species | |
See text. | |
Synonyms | |
"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]
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Liberibacter | |
---|---|
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 | |
Domain: | |
Phylum: | |
Class: | |
Order: | |
Family: | |
Genus: | Liberibacter Fagen et al. 2014
[1]
|
Species | |
See text. | |
Synonyms | |
"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]
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cite journal}}
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