COPPER DEPENDING INHIBITION OF Xanthomonas sp BY THE SIDEROPHORE PYOCHELIN.

ADLER CONRADO; POMARES FERNANDA; CORBALAN NATALIA; DE CRISTOBAL RE; VINCENT PAULA

San Miguel de Tucumán

Congreso; SAIB; 2010

SAIB

In a screening for metabolites produced by soil and rhizospherebacteria capable of inhibiting Xanthomonas citri pv citri weidentified strains from the Pseudomonas genus able to inhibit thispathogen. After purification we were able to identify the activecompound as pyochelin. Since this compound is a siderophorecapable of chelating metal ions, we tested if the inhibitory effectcould be dependent on metal ion chelation. We observed no reduction on MICs when Fe+3, Zn+2, Mg+2 were added but wesignificantly reduced its inhibitory effect by adding copper. Sincepyochelin is active against Xanthomonas species but not activeagainst other gram negatives such as E. coli and Salmonella, wethought that resistant strains might have siderophores that wouldallow them to overcome the presence of pyochelin. Indeed, weobserved that E. coli became sensitive to pyochelin when thebiosynthesis of enterochelin was impaired by a mutation in the entEgene. In addition, we observed Xanthomonas protection againstpyochelin when we added partially purified enterochelin. This E.coli siderophore is reported to be involved in copper reductionmaking it more available for cell growth, so we hypothesized that areducer agent as ascorbate would mimic enterobactin in reducingCu+2 to Cu+1 and therefore would protect sensitive strains topyochelin. We observed such protection in sensitive strains.