Title: Effect of Iron on Biological Control of Fire Blight by Pseudomonasfluorescens A506. Abstrard:

Competitive exclusion has been the mechanism hypothesized to account for the biological control of fire blight disease of pear and apple by the bacterium Pseudomonas fluorescens A506 (A506). Recent laboratory assays demonstrated, however, that A506 produces an antibiotic that is toxic to the fire blight pathogen, Erwinia amylovora, when cultured on media amended with iron (Fe2 or Fe3). This study investigated this iron-dependent antibiosis by A506 by: 1) examining bioavailability of iron to A506 on blossom surfaces, 2) mutagenizing A506 to disrupt genes involved in antibiotic production, and 3) evaluating suppression of fire blight by A506 when co-treated with an iron chelate (FeEDDHA). Bioavailability of iron on blossoms was investigated with an iron biosensor [iron-regulated promoter (pvd) fused to an ice nucleation reporter gene (inaZ)] in A506. A506 (pvd-inaZ) expressed high ice nucleation activity (INA) on blossoms indicating a low-iron environment unlikely to induce antibiosis by A506. Redacted for Privacy Redacted for Privacy Spraying blossoms with FeEDDHA at concentrations? 0.1 mM significantly suppresse