Comparative genomes of Chlamydia pneumoniae and C-trachomatis

Chlamydia are obligate intracellular eubacteria that are phylogenetically s eparated from other bacterial divisions. C. trachomatis and C. pneumoniae a re both pathogens of humans but differ in their tissue tropism and spectrum of diseases. C. pneumoniae is a newly recognized species of Chlamydia that is a natural pathogen of humans(1), and causes pneumonia and bronchitis. I n the United States, approximately 10% of pneumonia cases and 5% of bronchi tis cases are attributed to C. pneumoniae infection(2). Chronic disease may result following respiratory-acquired infection, such as reactive airway d isease(3), adult-onset asthma(4) and potentially lung cancer(5). In additio n, C, pneumoniae infection has been associated with atherosclerosis(6-11). C trachomatis infection causes trachoma, an ocular infection that leads to blindness, and sexually transmitted diseases such as pelvic inflammatory di sease, chronic pelvic pain, ectopic pregnancy and epididymitis(12), Althoug h relatively little is known about C. trachomatis biology(13), even less is known concerning C. pneomoniae. Comparison of the C. pneumoniae genome wit h the C. trachomatis genome(14) will provide an understanding of the common biological processes required for infection and survival in mammalian cell s. Genomic differences are implicated in the unique properties that differe ntiate the two species in disease spectrum, Analysis of the 1,230,230-nt C. pneumoniae genome revealed 214 protein-coding sequences not found in C. tr achomatis, most without homologues to other known sequences. Prominent comp arative findings include expansion of a novel family of 21 sequence-variant outer-membrane proteins, conservation of a type-ill secretion virulence sy stem, three serine/threonine protein kinases and a pair of parologous phosp holipase-D-like proteins, additional purine and biotin biosynthetic capabil ity, a homologue for aromatic amino acid (tryptophan) hydroxylase and the l oss of tryptophan biosynthesis genes.