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Effect of siderophores, catecholamines, and catechol compounds on Listeria spp. Growth in iron-complexed medium.

Almost all bacteria require iron for growth and virulence expression. However, Listeria spp. do not produce any siderophore for iron acquisition. Representative strains of each of the six species of Listeria were examined for their ability to use various compounds as iron suppliers in iron-restricted medium. Here we show that L. monocytogenes, L. innocua, L. ivanovii, L. welshimeri, L. seeligeri, and L. grayi were able to use exogenous siderophores and various catechol ligands, including catecholamines, to overcome growth inhibition induced by tropolone, an iron chelating agent. In contrast, no growth promoting effect was observed with normetanephrine or 4-hydroxy-3-methoxyphenylglycol-piperazine salt, which indicates that the o-diphenol function of the ligand must be free to allow iron acquisition. Furthermore, we demonstrate that catecholamines do not act through specific bacterial receptors, because no difference in growth stimulation was observed between [+]- and [-]-norepinephrine. These results show that utilization of a variety of catechol compounds to acquire iron is a general phenomenon in the genus Listeria.