Aidan Budd*, Stephanie Blandin*, Elena A Levashina† and Toby J Gibson* Addresses: *European Molecular Biology Laboratory, 69012 Heidelberg, Germany. †UPR 9022 du CNRS, IBMC, rue René Descartes, F-67087 Strasbourg CEDEX, France. Correspondence: Toby J Gibson. E-mail: reviews Published: 26 May 2004 Genome Biology 2004, 5:R38 The electronic version of this article is the complete one and can be found online at Received: 20 February 2004 Revised: 2 April 2004 Accepted: 8 April 2004 © 2004 Budd et al.; licensee BioMed Central Ltd. This is an Open Access article: verbatim copying and redistribution of this article are permitted in all media for any purpose,. | Research Open Access Bacterial a2-macroglobulins colonization factors acquired by horizontal gene transfer from the metazoan genome Aidan Budd Stephanie Blandin Elena A Levashina and Toby J Gibson Addresses European Molecular Biology Laboratory 69012 Heidelberg Germany. tUPR 9022 du CNRS IBMC rue René Descartes F-67087 Strasbourg CEDEX France. Correspondence Toby J Gibson. E-mail Published 26 May 2004 Genome Biology 2004 5 R38 The electronic version of this article is the complete one and can be found online at http 2004 5 6 R38 Received 20 February 2004 Revised 2 April 2004 Accepted 8 April 2004 2004 Budd et al. licensee BioMed Central Ltd. This is an Open Access article verbatim copying and redistribution of this article are permitted in all media for any purpose provided this notice is preserved along with the article s original URL. Abstract Background Invasive bacteria are known to have captured and adapted eukaryotic host genes. They also readily acquire colonizing genes from other bacteria by horizontal gene transfer. Closely related species such as Helicobacter pylori and Helicobacter hepaticus which exploit different host tissues share almost none of their colonization genes. The protease inhibitor a2-macroglobulin provides a major metazoan defense against invasive bacteria trapping attacking proteases required by parasites for successful invasion. Results Database searches with metazoan a2-macroglobulin sequences revealed homologous sequences in bacterial proteomes. The bacterial a2-macroglobulin phylogenetic distribution is patchy and violates the vertical descent model. Bacterial a2-macroglobulin genes are found in diverse clades including purple bacteria proteobacteria fusobacteria spirochetes bacteroidetes deinococcids cyanobacteria planctomycetes and thermotogae. Most bacterial species with bacterial a2-macroglobulin genes exploit higher eukaryotes multicellular plants and animals as hosts. Both pathogenically .
