Fire blight, caused by Erwinia amylovora, is a destructive bacterial disease affecting pear and apple trees. The bio- control ability of Pseudomonas fluorescens EK007 suppresses E. amylovora through competitive exclusion. In this study, EK007 was isolated from the pear phylloplane and characterized as an effective biological agent through antibacterial compounds. To identify the mechanisms underlying EK007\\\\\\\'s biocontrol activity, physiological tests, transposon insertion mutant libraries, allelic exchange, and whole-genome sequencing were performed. A trans- poson mutation in the massC homolog gene, part of the massetolide A lipopeptide biosynthesis cluster, reduced the biocontrol efficiency. Allelic exchange confirmed cyclic lipopeptide (CLP) as part of the mechanism. Addi- tionally, a gacA mutant isolated by transposon mutagenesis showed deficient inhibition activity. Culture condi- tions and nutritional sources clearly influenced EK007\\\\\\\'s antimicrobial activity against E. amylovora. Growth yield generally correlated with antibiotic production, with amino acids and iron affecting production. Asparagine and aspartate shut down biocontrol activity. This study presents preliminary findings on a novel CLP that may con- tribute to EK007\\\\\\\'s antibacterial activity against E. amylovora. While EK007 shows promise as a biocontrol candi- date compared to related strains, these results are based solely on in vitro studies, highlighting the need for fur- ther investigations to evaluate its efficacy in natural environments.

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