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Applied and Environmental Microbiology, November 2005, p. 6947-6953, Vol. 71, No. 11
0099-2240/05/$08.00+0     doi:10.1128/AEM.71.11.6947-6953.2005
Copyright © 2005, American Society for Microbiology. All Rights Reserved.

Iron Uptake Mechanisms in the Fish Pathogen Tenacibaculum maritimum

Ruben Avendaño-Herrera, Alicia E. Toranzo,* Jesús L. Romalde, Manuel L. Lemos, and Beatriz Magariños

Departamento de Microbiología y Parasitología, Facultad de Biología and Instituto de Acuicultura, Universidad de Santiago, 15782 Santiago de Compostela, Spain

Received 10 May 2005/ Accepted 5 July 2005

We present here the first evidence of the presence of iron uptake mechanisms in the bacterial fish pathogen Tenacibaculum maritimum. Representative strains of this species, with different serotypes and origins, were examined. All of them were able to grow in the presence of the chelating agent ethylenediamine-di- (o-hydroxyphenyl acetic acid) (EDDHA) and also produced siderophores. Cross-feeding assays suggest that the siderophores produced are closely related. In addition, all T. maritimum strains utilized transferrin, hemin, hemoglobin, and ferric ammonic citrate as iron sources when added to iron-deficient media. Whole cells of all T. maritimum strains, grown under iron-supplemented or iron-restricted conditions, were able to bind hemin, indicating the existence of constitutive binding components located at the T. maritimum cell surface. This was confirmed by the observation that isolated total and outer membrane proteins from all of the strains, regardless of the iron levels of the media, were able to bind hemin, with the outer membranes showing the strongest binding. proteinase K treatment of whole cells did not affect the hemin binding, indicating that, in addition to proteins, some protease-resistant components could also bind hemin. At least three outer membrane proteins were induced in iron-limiting conditions, and all strains, regardless of their serotype, showed a similar pattern of induced proteins. The results of the present study suggest that T. maritimum possesses at least two different systems of iron acquisition: one involving the synthesis of siderophores and another that allows the utilization of heme groups as iron sources by direct binding.


* Corresponding author. Mailing address: Departamento de Microbiología y Parasitología, Facultad de Biología and Instituto de Acuicultura, Universidad de Santiago, 15782 Santiago de Compostela, Spain. Phone: 34-981-563100, ext. 13255. Fax: 34-981-596904. E-mail: mpaetjlb{at}usc.es.


Applied and Environmental Microbiology, November 2005, p. 6947-6953, Vol. 71, No. 11
0099-2240/05/$08.00+0     doi:10.1128/AEM.71.11.6947-6953.2005
Copyright © 2005, American Society for Microbiology. All Rights Reserved.