Provided for non-commercial research and educational use only. Not for reproduction, distribution or commercial use. This chapter was originally published in the book ADVANCES IN APPLIED MICROBIOLOGY, Vol. 72, published by Elsevier, and the attached copy is provided by Elsevier for the author's benefit and for the benefit of the author's institution, for non-commercial research and educational use including without limitation use in instruction at your institution, sending it to specific colleagues who know you, and providing a copy to your institution’s administrator. All other uses, reproduction and distribution, including without limitation commercial reprints, selling or licensing copies or access, or posting on open internet sites, your personal or institution’s website or repository, are prohibited. For exceptions, permission may be sought for such use through Elsevier's permissions site at: http://www.elsevier.com/locate/permissionusematerial From: Walter J. Dobrogosz, Trent J. Peacock, and Hosni M. Hassan, Evolution of the Probiotic Concept: From Conception to Validation and Acceptance in Medical Science In Allen I. Laskin, Sima Sariaslani and Geoffrey M. Gadd editor: ADVANCES IN APPLIED MICROBIOLOGY, Vol. 72, Burlington: Academic Press, 2010, pp.1-41. ISBN: 978-0-12-380989-6 © Copyright 2010, Elsevier Inc. Academic Press.