Penicillin Trunk Injection Affects Bacterial Community Structure in Citrus Trees

Area of Science:

• Microbiology
• Plant Pathology
• Genomics

Background:

• Huanglongbing (HLB), caused by Candidatus Liberibacter asiaticus (CLas), is a devastating citrus disease globally.
• Previous research indicated penicillin trunk injections reduce CLas titers and HLB symptoms.
• The impact of antibiotics on the entire citrus microbial community, including interactions with CLas, remains largely unexamined.

Purpose of the Study:

• To investigate the effects of penicillin trunk injections on rhizospheric and endophytic bacterial communities in grapefruit trees.
• To understand how different penicillin concentrations influence the citrus microbiome and interspecific microbial associations.

Main Methods:

• Field and greenhouse experiments using grapefruit trees treated with varying penicillin concentrations (0, 1000, 6000 mg L⁻¹).
• Culture-independent high-throughput sequencing of 16S rRNA genes from root and petiole DNA.
• Analysis of bacterial community structure using Principal Coordinates Analysis (PCoA) and pairwise linear discriminant analysis (LDA).
• Network analysis to assess changes in interspecific microbial associations.

Main Results:

• No significant differences in overall bacterial community structure were detected among treatments via PCoA.
• Pairwise LDA identified significant differences in the relative abundance of specific bacterial taxa, including CLas, across treatments.
• Network analysis revealed substantial alterations in root bacterial community structure due to penicillin, primarily by affecting microbial associations.

Conclusions:

• Penicillin trunk injections significantly impact the citrus root microbiome structure and interspecific microbial relationships, beyond just reducing CLas.
• This research provides novel insights into the ecological consequences of antimicrobial treatments within the complex citrus holobiont.
• Understanding these microbial community shifts is crucial for developing sustainable HLB management strategies.