<i>Erwinia chrysanthemi</i> requires a second iron transport route dependent of the siderophore achromobactin for extracellular growth and plant infection

DOI Web Site Web Site 2 Citations

Abstract

<jats:title>Summary</jats:title><jats:p>Full virulence of the pectinolytic enterobacterium <jats:italic>Erwinia chrysanthemi</jats:italic> strain 3937 depends on the production <jats:italic>in planta</jats:italic> of the catechol‐type siderophore chrysobactin. Under iron‐limited conditions, <jats:italic>E. chrysanthemi</jats:italic> synthesizes a second siderophore called achromobactin belonging to the hydroxy/carboxylate class of siderophore. In this study, we cloned and functionally characterized a 13 kb long operon comprising seven genes required for the biosynthesis (<jats:italic>acs</jats:italic>) and extracellular release (<jats:italic>yhcA</jats:italic>) of achromobactin, as well as the gene encoding the specific outer membrane receptor for its ferric complex (<jats:italic>acr</jats:italic>). The promoter of this operon was negatively regulated by iron. In a <jats:italic>fur</jats:italic> null mutant, transcriptional fusions to the <jats:italic>acsD</jats:italic> and <jats:italic>acsA</jats:italic> genes were constitutively expressed. Band shift assays showed that the purified <jats:italic>E. chrysanthemi</jats:italic> Fur repressor protein specifically binds <jats:italic>in vitro</jats:italic> to the promoter region of the <jats:italic>acsF</jats:italic> gene confirming that the metalloregulation of the achromobactin operon is achieved directly by Fur. The temporal production of achromobactin in iron‐depleted bacterial cultures was determined: achromobactin is produced before chrysobactin and its production decreases as that of chrysobactin increases. Pathogenicity tests performed on African violets showed that achromobactin production contributes to the virulence of <jats:italic>E. chrysanthemi.</jats:italic> Thus, during infection, synthesis of these two different siderophores allows <jats:italic>E. chrysanthemi</jats:italic> cells to cope with the fluctuations of iron availability encountered within plant tissues. Interestingly, iron transport mediated by achromobactin or a closely related siderophore probably exists in other phytopathogenic bacterial species such as <jats:italic>Pseudomonas syringae</jats:italic>.</jats:p>

Journal

Citations (2)*help

See more

Keywords

Report a problem

Back to top