11. Voigt A, Schofl G, Saluz HP (2012) The Chlamydia psittaci genome: a comparative analysis of intracellular pathogens. PLoS One 7: e35097. 12. Swanson KA, Taylor LD, Frank SD, Sturdevant GL, Fischer ER, et al. (2009) Chlamydia trachomatis polymorphic membrane protein D is an oligomeric autotransporter with a higher-order structure. Infect Immun 77: 508–516. 13. Aitken ID, Longbottom D (2007) Chlamydial abortion. In: Aitken ID, editors. Diseases of Sheep. Oxford: Blackwell Publishing. pp. 105–111. 14. Grimwood J, Stephens RS (1999) Computational analysis of the polymorphic membrane protein superfamily of Chlamydia trachomatis and Chlamydia pneumoniae. Microb Comp Genomics 4: 187–201. 15. Graham SP, Jones GE, MacLean M, Livingstone M, Entrican G (1995) Recombinant ovine interferon gamma inhibits the multiplication of Chlamydia psittaci in ovine cells. J Comp Pathol 112: 185–195. 16. Vretou E, Loutrari H, Mariani L, Costelidou K, Eliades P, et al. (1996) Diversity among abortion strains of Chlamydia psittaci demonstrated by inclusion morphology, polypeptide profiles and monoclonal antibodies. Vet Microbiol 51: 275–289. 17. Laemmli UK (1970) Cleavage of structural proteins during the assembly of the head of bacteriophage T4. Nature 227: 680–685. 18. Batycka M, Inglis NF, Cook K, Adam A, Fraser-Pitt D, et al. (2006) Ultra-fast tandem mass spectrometry scanning combined with monolithic column liquid chromatography increases throughput in proteomic analysis. Rapid Commun Mass Spectrom 20: 2074–2080. 19. Taylor GK, Goodlett DR (2005) Rules governing protein identification by mass spectrometry. Rapid Commun Mass Spectrom 19: 3420. Processing of C. abortus Pmp18D 20. Edgar RC (2004) MUSCLE: multiple sequence alignment with high accuracy and high throughput. Nucleic Acids Res 32: 1792–1797. 21. Lin K, Simossis VA, Taylor WR, Heringa J (2005) A simple and fast secondary structure prediction method using hidden neural networks. Bioinformatics 21: 152–159. 22. Castresana J (2000) Selection of conserved blocks from multiple alignments for their use in phylogenetic analysis. Mol Biol Evol 17: 540–552. 23. Ronquist F, Huelsenbeck JP (2003) MrBayes 3: Bayesian phylogenetic inference under mixed models. Bioinformatics 19: 1572–1574. 24. Milne I, Lindner D, Bayer M, Husmeier D, McGuire G, et al. (2009) TOPALi v2: a rich graphical interface for evolutionary analyses of multiple alignments on HPC clusters and multi-core desktops. Bioinformatics 25: 126–127. 25. Wheelhouse N, Aitchison K, Spalding L, Livingstone M, Longbottom D (2009) Transcriptional analysis of in vitro expression patterns of Chlamydophila abortus polymorphic outer membrane proteins during the chlamydial developmental cycle. Vet Res 40: 47. 26. Wheelhouse N, Sait M, Wilson K, Aitchison K, McLean K, et al. (2012) Expression patterns of five polymorphic membrane proteins during the Chlamydia abortus developmental cycle. Vet Microbiol. 27. Kiselev AO, Stamm WE, Yates JR, Lampe MF (2007) Expression, processing, and localization of PmpD of Chlamydia trachomatis serovar L2 during the chlamydial developmental cycle. PLoS ONE 2: e568. 28. Wehrl W, Brinkmann V, Jungblut PR, Meyer TF, Szczepek AJ (2004) From the inside out - processing of the Chlamydial autotransporter PmpD and its role in bacterial adhesion and activation of human host cells. Mol Microbiol 51: 319– 334. PLOS ONE | www.plosone.org 7 November 2012 | Volume 7 | Issue 11 | e49190