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United States Department of Agriculture

Agricultural Research Service

Research Project: EMERGING DISEASES OF CITRUS, VEGETABLES, AND ORNAMENTALS

Location: Subtropical Plant Pathology Research

Title: Deciphering the bacterial microbiome of citrus plants in response to ‘Candidatus Liberibacter asiaticus’-infection and antibiotic treatment

Authors
item Zhang, Muqing -
item Powell, Charles -
item Benyon, Lesley
item Zhou, Hui -
item Duan, Ping

Submitted to: PLoS One
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: July 1, 2013
Publication Date: August 1, 2013
Repository URL: http://doi:10.1371/journal.pone.0082248
Citation: Zhang, M., Powell, C., Benyon, L.S., Zhou, H., Duan, Y. 2013. Deciphering the bacterial microbiome of citrus plants in response to ‘Candidatus Liberibacter asiaticus’-infection and antibiotic treatment. PLoS One. 8(12): e82248.

Interpretive Summary: Huanglongbing (HLB), the most devastating citrus disease worldwide and the pathogen in the USA is Candidatus Liberibacter asiaticus (Las). The bacterial microbiome of citrus after Las-infection and treatments with ampicillin (Amp) and gentamicin (Gm) was characterized using the Phylochip™ G3 array. This microarray assesses microbial community structure based on amplified 16S rRNA gene sequences. The results revealed that 7,407 of over 50,000 known OTUs (Operational Taxonomic Units) in 53 phyla were detected in the citrus leaf midribs. The OTUs are entities whose affinities are studied by numerical taxonomy. Depending on the level and the type of investigation an OTU may be of any taxonomic rank or an individual organism. Five phyla were dominant, Proteobacteria (38.7%), Firmicutes (29.0%), Actinobacteria (16.1%), Bacteroidetes (6.2%) and Cyanobacteria (2.3%), and the OTU representing ‘Candidatus Liberibacter’ had a higher titer in plants graft-inoculated with Las-infected scions treated with Gm at 100 mg/L and water (control) than plants graft-inoculated with Las-infected scions treated with Amp at 100 mg/L and healthy controls. This indicated that Amp, but not Gm, was effective in eliminating the Las bacterium. The PhyloChip array also demonstrated that more OTUs, at a higher abundance, were detected in the Gm-treated plants than in the other treatment and the controls.

Technical Abstract: Huanglongbing (HLB), the most devastating citrus disease worldwide, is vectored by phloem-feeding insects, and the pathogen in the USA is Candidatus Liberibacter asiaticus (Las). The bacterial microbiome of citrus after Las-infection and treatments with ampicillin (Amp) and gentamicin (Gm) was characterized by Phylochip-based metagenomics. The results revealed that 7,407 of over 50,000 known OTUs (Operational Taxonomic Units) in 53 phyla were detected in the citrus leaf midribs, of which five phyla were dominant, Proteobacteria (38.7%), Firmicutes (29.0%), Actinobacteria (16.1%), Bacteroidetes (6.2%) and Cyanobacteria (2.3%). The OTU_62806, representing ‘Candidatus Liberibacter’, was present with a high titer in the plants graft-inoculated with Las-infected scions treated with Gm at 100 mg/L and water (control). However, Las had undetectable levels and was absent in the plants graft-inoculated with Las-infected scions treated with Amp at 100 mg/L and healthy controls. The PhyloChip array also demonstrated that more OTUs, at a higher abundance, were detected in the Gm-treated plants than in the other treatment and the controls. Pairwise comparisons indicated that 23 OTUs from the Achromobacter sp. and 12 OTUs from the Methylobacterium sp. were more abundant in the healthy control (CK2) and the disease control (CK1), respectively. Ten abundant OTUs from the Stenotrophomonas sp., but not from the Xanthomonas and Xylella families of Xanthomonadaceae, were detected only in the Amp-treatment.

Last Modified: 9/21/2014
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