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Characterization of the microbial community structure in Candidatus Liberibacter asiaticus-infected citrus plants treated with antibiotics in the field.

Zhang M, Powell CA, Guo Y, Benyon L, Duan Y - BMC Microbiol. (2013)

Bottom Line: Both antibiotic treatments resulted in significantly lower Las bacterial titers (Pr<0.05) and hybridization scores.In the antibiotic treated samples, the number of OTUs decreased to a total of 5,599.In addition, the level of bacterial diversity found in the leaf midribs of field citrus was greater than previously described.

View Article: PubMed Central - HTML - PubMed

Affiliation: Indian River Research and Education Center, IFAS-UF, Fort Pierce, FL 34945, USA.

ABSTRACT

Background: Huanglongbing (HLB) is a worldwide devastating disease of citrus. There are no effective control measures for this newly emerging but century-old disease. Previously, we reported a combination of Penicillin G and Streptomycin was effective in eliminating or suppressing the associated bacterium, 'Candidatus Liberibacter asiaticus' (Las).

Results: Here we report the bacterial composition and community structure in HLB-affected citrus plants during a growing season and while being treated with antibiotic combinations PS (Penicillin G and Streptomycin) and KO (Kasugamycin and Oxytetracycline) using the Phylochip™ G3 array. Both antibiotic treatments resulted in significantly lower Las bacterial titers (Pr<0.05) and hybridization scores. Of the 50,000+ available operational taxonomic units (OTUs) on PhyloChip™ G3, 7,028 known OTUs were present in citrus leaf midribs. These OTUs were from 58 phyla, of which five contained 100 or more OTUs, Proteobacteria (44.1%), Firmicutes (23.5%), Actinobacteria (12.4%), Bacteroidetes (6.6%) and Cyanobacteria (3.2%). In the antibiotic treated samples, the number of OTUs decreased to a total of 5,599. The over-all bacterial diversity decreased with the antibiotic treatments, as did the abundance of 11 OTUs within Proteobacteria, Firmicutes, Bacteroidetes and Planctomycetes. Within the Proteobacteria, ten OTUs representing the class γ-proteobacteria increased in abundance after four months of treatment, when the Las bacterium was at its lowest level in the HLB-affected citrus field plants.

Conclusions: Our data revealed that Proteobacteria was constantly the dominant bacterial phylum recovered from citrus leaf midribs, with the α-proteobacterial and the γ-proteobacterial classes vying for prevalence. In addition, the level of bacterial diversity found in the leaf midribs of field citrus was greater than previously described. Bacterial cells in close proximity may be able to modify their microenvironment, making the composition of the microbial community an important factor in the ability of Las to cause HLB progression. A low Las level was seen as an annual fluctuation, part of the bacterial population dynamics, and as a response to the antibiotic treatments.

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Operational taxonomic units (OTUs) for families detected by PhyloChip™ G3 hybridization of Huanglongbing (HLB)-affected citrus. The citrus plants were treated with different antibiotic combinations and leaf samples were collected at different times (October 2010, April 2011 and October 2011) over a year. Proportions of OTUs for the most highly represented families are represented over the sampling time points. The size of each block in the family abundance bar chart represents the number of detected OTUs in that family relative to the total number of OTUs detected with the same treatment over the sampling time points. PS: 5 g/tree penicillin G potassium and 0.5 g/tree streptomycin; KO: 2 g/tree oxytetracycline and 1.0 g/tree kasugamycin; and CK: water as control.
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Figure 4: Operational taxonomic units (OTUs) for families detected by PhyloChip™ G3 hybridization of Huanglongbing (HLB)-affected citrus. The citrus plants were treated with different antibiotic combinations and leaf samples were collected at different times (October 2010, April 2011 and October 2011) over a year. Proportions of OTUs for the most highly represented families are represented over the sampling time points. The size of each block in the family abundance bar chart represents the number of detected OTUs in that family relative to the total number of OTUs detected with the same treatment over the sampling time points. PS: 5 g/tree penicillin G potassium and 0.5 g/tree streptomycin; KO: 2 g/tree oxytetracycline and 1.0 g/tree kasugamycin; and CK: water as control.

Mentions: The proportions of OTUs for the most highly represented families (Figure 4) showed a large variation in the number of OTUs detected in the Comamonadaceae, Staphylococcaceae, Corynebacteriaceae, and Flavobacteriaceae families. In accordance with the Las bacterial titers, the amount of OTUs in Comamonadaceae significantly decreased in April 2011 when compared to the other sampling time points (October 2010 and October 2011); however, the amount of OTUs in the Enterobacteriaceae and Aquabacteriaceae families significantly increased.


Characterization of the microbial community structure in Candidatus Liberibacter asiaticus-infected citrus plants treated with antibiotics in the field.

Zhang M, Powell CA, Guo Y, Benyon L, Duan Y - BMC Microbiol. (2013)

Operational taxonomic units (OTUs) for families detected by PhyloChip™ G3 hybridization of Huanglongbing (HLB)-affected citrus. The citrus plants were treated with different antibiotic combinations and leaf samples were collected at different times (October 2010, April 2011 and October 2011) over a year. Proportions of OTUs for the most highly represented families are represented over the sampling time points. The size of each block in the family abundance bar chart represents the number of detected OTUs in that family relative to the total number of OTUs detected with the same treatment over the sampling time points. PS: 5 g/tree penicillin G potassium and 0.5 g/tree streptomycin; KO: 2 g/tree oxytetracycline and 1.0 g/tree kasugamycin; and CK: water as control.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC3672075&req=5

Figure 4: Operational taxonomic units (OTUs) for families detected by PhyloChip™ G3 hybridization of Huanglongbing (HLB)-affected citrus. The citrus plants were treated with different antibiotic combinations and leaf samples were collected at different times (October 2010, April 2011 and October 2011) over a year. Proportions of OTUs for the most highly represented families are represented over the sampling time points. The size of each block in the family abundance bar chart represents the number of detected OTUs in that family relative to the total number of OTUs detected with the same treatment over the sampling time points. PS: 5 g/tree penicillin G potassium and 0.5 g/tree streptomycin; KO: 2 g/tree oxytetracycline and 1.0 g/tree kasugamycin; and CK: water as control.
Mentions: The proportions of OTUs for the most highly represented families (Figure 4) showed a large variation in the number of OTUs detected in the Comamonadaceae, Staphylococcaceae, Corynebacteriaceae, and Flavobacteriaceae families. In accordance with the Las bacterial titers, the amount of OTUs in Comamonadaceae significantly decreased in April 2011 when compared to the other sampling time points (October 2010 and October 2011); however, the amount of OTUs in the Enterobacteriaceae and Aquabacteriaceae families significantly increased.

Bottom Line: Both antibiotic treatments resulted in significantly lower Las bacterial titers (Pr<0.05) and hybridization scores.In the antibiotic treated samples, the number of OTUs decreased to a total of 5,599.In addition, the level of bacterial diversity found in the leaf midribs of field citrus was greater than previously described.

View Article: PubMed Central - HTML - PubMed

Affiliation: Indian River Research and Education Center, IFAS-UF, Fort Pierce, FL 34945, USA.

ABSTRACT

Background: Huanglongbing (HLB) is a worldwide devastating disease of citrus. There are no effective control measures for this newly emerging but century-old disease. Previously, we reported a combination of Penicillin G and Streptomycin was effective in eliminating or suppressing the associated bacterium, 'Candidatus Liberibacter asiaticus' (Las).

Results: Here we report the bacterial composition and community structure in HLB-affected citrus plants during a growing season and while being treated with antibiotic combinations PS (Penicillin G and Streptomycin) and KO (Kasugamycin and Oxytetracycline) using the Phylochip™ G3 array. Both antibiotic treatments resulted in significantly lower Las bacterial titers (Pr<0.05) and hybridization scores. Of the 50,000+ available operational taxonomic units (OTUs) on PhyloChip™ G3, 7,028 known OTUs were present in citrus leaf midribs. These OTUs were from 58 phyla, of which five contained 100 or more OTUs, Proteobacteria (44.1%), Firmicutes (23.5%), Actinobacteria (12.4%), Bacteroidetes (6.6%) and Cyanobacteria (3.2%). In the antibiotic treated samples, the number of OTUs decreased to a total of 5,599. The over-all bacterial diversity decreased with the antibiotic treatments, as did the abundance of 11 OTUs within Proteobacteria, Firmicutes, Bacteroidetes and Planctomycetes. Within the Proteobacteria, ten OTUs representing the class γ-proteobacteria increased in abundance after four months of treatment, when the Las bacterium was at its lowest level in the HLB-affected citrus field plants.

Conclusions: Our data revealed that Proteobacteria was constantly the dominant bacterial phylum recovered from citrus leaf midribs, with the α-proteobacterial and the γ-proteobacterial classes vying for prevalence. In addition, the level of bacterial diversity found in the leaf midribs of field citrus was greater than previously described. Bacterial cells in close proximity may be able to modify their microenvironment, making the composition of the microbial community an important factor in the ability of Las to cause HLB progression. A low Las level was seen as an annual fluctuation, part of the bacterial population dynamics, and as a response to the antibiotic treatments.

Show MeSH
Related in: MedlinePlus