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Infection and Immunity, August 2000, p. 4498-4504, Vol. 68, No. 8
0019-9567/00/$04.00+0
Copyright © 2000, American Society for Microbiology. All rights reserved.

Requirement of the Pseudomonas aeruginosa tonB Gene for High-Affinity Iron Acquisition and Infection

Hiroyuki Takase,* Hironobu Nitanai, Kazuki Hoshino, and Tsuyoshi Otani

New Product Research Laboratories I, Daiichi Pharmaceutical Co., Ltd., Tokyo 134-8630, Japan

Received 11 February 2000/Returned for modification 13 April 2000/Accepted 8 May 2000

To investigate the contribution of the TonB protein to high-affinity iron acquisition in Pseudomonas aeruginosa, we constructed tonB-inactivated mutants from strain PAO1 and its derivative deficient in producing the siderophores pyoverdin and pyochelin. The tonB mutants could not grow in a free-iron-restricted medium prepared by apotransferrin addition, even though the medium was supplemented with each purified siderophore or with a heme source (hemoglobin or hemin). The tonB inactivation was shown to make P. aeruginosa unable to acquire iron from the transferrin with either siderophore. Introduction of a plasmid carrying the intact tonB gene restored growth of the tonB mutant of PAO1 in the free-iron-restricted medium without any supplements and restored growth of the tonB mutant of the siderophore-deficient derivative in the medium supplemented with pyoverdin, pyochelin, hemoglobin, or hemin. In addition, animal experiments showed that, in contrast to PAO1, the tonB mutant of PAO1 could not grow in vivo, such as in the muscles and lungs of immunosuppressed mice, and could not kill any of the animals. The in vivo growth ability and lethal virulence were also restored by introduction of the tonB-carrying plasmid in the tonB mutant. These results indicate clearly that the intact tonB gene---and, therefore, the TonB protein encoded by it---is essential for iron acquisition mediated by pyoverdin and pyochelin and via heme uptake in P. aeruginosa and suggest that the TonB-dependent iron acquisition may be essential for P. aeruginosa to infect the animal host.

* Corresponding author. Mailing address: New Product Research Laboratories I, Daiichi Pharmaceutical Co., Ltd., 16-13, Kita-Kasai 1-chome, Edogawa-ku, Tokyo 134-8630, Japan. Phone: 81-3-3680-0151. Fax: 81-3-5696-8344. E-mail: takas4px{at}daiichipharm.co.jp.

Infection and Immunity, August 2000, p. 4498-4504, Vol. 68, No. 8
0019-9567/00/$04.00+0
Copyright © 2000, American Society for Microbiology. All rights reserved.


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