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POSTERS: Bacteriology II

P-014 - A BACILLUS-PRODUCED ANTIBIOTIC, AMICOUMACIN B, IS A POTENTIAL TOOL IN THE FIGHT AGAINST CITRUS HUANGLONGBING DISEASE

Tuesday, August 5, 2025
9:30 AM - 10:15 AM HST
Location: Exhibit Hall 3
Abstract Text:

Huanglongbing (HLB) is a devastating citrus disease caused by the phloem-limited and unculturable bacterium Candidatus Liberibacter asiaticus (CLas), and transmitted by the psyllid, Diaphorina citri. Despite extensive research, effective and sustainable solutions for managing HLB remain elusive. Oxytetracycline is currently used as an emergency measure, but there is an urgent need for alternative compounds to rotate or replace OTC. In this study, we identified amicoumacin B, an antimicrobial compound produced by Bacillus safensis CB729, a bacterium isolated from the citrus microbiome and demonstrated its ability to suppress CLas. Genome mining of Bacillus safensis CB729, combined with LCMS analysis, revealed the presence of amicoumacin A and B, along with derivative compounds, in fractions inhibitory to Liberibacter crescens, a culturable surrogate for CLas. Amicoumacins are a group of secondary metabolites, originally discovered in Bacillus, and display strong antibiotic and bioactive properties against a range of microorganisms with medical, agricultural and environmental interest. We tested commercially available synthetic amicoumacin A and B, along with a mixture of amicoumacins, against L. crescens and CLas and determined the minimal inhibitory concentrations (MICs) of amicoumacin A and B against L. crescens. Moreover, amicoumacin B and the amicoumacin mixture demonstrated a significant reduction of CLas populations in ex vivo assays. This work highlights the potential of amicoumacins as promising natural products for the management of HLB.