Deciphering the bacterial microbiome in huanglongbing-affected citrus treated with thermotherapy and sulfonamide antibiotics

Authors: YANG, C - Guangxi Citrus Research Institute; POWELL, C - University Of Florida; Duan, Ping; Shatters, Robert - Bob; FANG, J - Fujian Agriculture And Forest University; ZHANG, M - Guangxi Citrus Research Institute

Submitted to: PLOS ONE
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/26/2016
Publication Date: 5/12/2016
Citation: Yang, C., Powell, C.A., Duan, Y., Shatters, R.G., Fang, J., Zhang, M.Q. 2016. Deciphering the bacterial microbiome in huanglongbing-affected citrus treated with thermotherapy and sulfonamide antibiotics. PLoS One. 11(5):e0155472. https://doi.org/10.1371/journal.pone.0155472.
DOI: https://doi.org/10.1371/journal.pone.0155472

Interpretive Summary: Thermal therapy has previously been demonstrated to kill the citrus greening disease causing bacterium in citrus trees. Treatment with various antibiotics has also been shown to reduce this bacterial population in trees. This study was conducted to evaluate the efficacy of combining thermal therapy and sulfonamide antibiotic treatment. Furthermore, this study evaluated how these treatments impacted the microbial community from citrus leaf samples. We demonstrated that the combination of heat and antibiotic induced the greatest reduction of the citrus greening bacterium and showed that this also caused a change in the entire bacterial community associated with the citrus leaves. Our study further develops an integrated strategy for combating huanglongbing (HLB), and also provides new insight into the bacterial community of HLB-affected citrus treated by heat and sulfonamide antibiotics.

Technical Abstract: Huanglongbing (HLB) is a serious citrus disease that threatens the citrus industry. In previous studies, sulfonamide antibiotics and heat treatment suppressed ‘Candidatus Liberibacter asiaticus’ (Las), but did not completely eliminate the Las. Furthermore, there are few reports studying the bacterial microbiome of HLB-affected citrus treated by heat and sulfonamide antibiotics. In this study, combinations of heat (45°C or 40°C) and sulfonamide treatment (sulfathiazole sodium–STZ, or sulfadimethoxine sodium—SDX) were applied to HLB-affected citrus. The bacterial microbiome of HLB-affected citrus following thermotherapy and/or chemotherapy was characterized by PhyloChipTMG3-based metagenomics. Our results showed that the combination of thermotherapy at 45°C and chemotherapy with STZ and SDX was more effective against HLB than thermotherapy alone, chemotherapy alone, or a combination of thermotherapy at 40°C and chemotherapy. The PhyloChipTMG3-based results indicated that 311 empirical Operational Taxonomic Units (eOTUs) were detected in 26 phyla. Cyanobacteria (18.01%) were dominant after thermo-chemotherapy. Thermotherapy at 45°C decreased eOTUs (64.43%) in leaf samples, compared with thermotherapy at 40°C (73.96%) or without thermotherapy (90.68%) and it also reduced bacterial family biodiversity. The eOTU in phylum Proteobacteria was reduced significantly and eOTU_28, representing “Candidatus Liberibacter,” was not detected following thermotherapy at 45°C. Following antibiotic treatment with SDX and STZ, there was enhanced abundance of specific eOTUs belonging to the families Streptomycetaceae, Desulfobacteraceae, Chitinophagaceae, and Xanthomonadaceae, which may be implicated in increased resistance to plant pathogens. Our study further develops an integrated strategy for combating HLB, and also provides new insight into the bacterial microbiome of HLB-affected citrus treated by heat and sulfonamide antibiotics.