Abstract
BackgroundChlamydiae are obligate intracellular bacteria comprising some of the most important bacterial pathogens of animals and humans. Although chlamydial outer membrane proteins play a key role for attachment to and entry into host cells, only few have been described so far. We developed a comprehensive, multiphasic in silico approach, including the calculation of clusters of orthologues, to predict outer membrane proteins using conservative criteria. We tested this approach using Escherichia coli (positive control) and Bacillus subtilis (negative control), and applied it to five chlamydial species; Chlamydia trachomatis, Chlamydia muridarum, Chlamydia (a.k.a. Chlamydophila) pneumoniae, Chlamydia (a.k.a. Chlamydophila) caviae, and Protochlamydia amoebophila.ResultsIn total, 312 chlamydial outer membrane proteins and lipoproteins in 88 orthologous clusters were identified, including 238 proteins not previously recognized to be located in the outer membrane. Analysis of their taxonomic distribution revealed an evolutionary conservation among Chlamydiae, Verrucomicrobia, Lentisphaerae and Planctomycetes as well as lifestyle-dependent conservation of the chlamydial outer membrane protein composition.ConclusionThis analysis suggested a correlation between the outer membrane protein composition and the host range of chlamydiae and revealed a common set of outer membrane proteins shared by these intracellular bacteria. The collection of predicted chlamydial outer membrane proteins is available at the online database pCOMP http://www.microbial-ecology.net/pcomp and might provide future guidance in the quest for anti-chlamydial vaccines.
Highlights
Chlamydiae are obligate intracellular bacteria comprising some of the most important bacterial pathogens of animals and humans
As chlamydiae are a unique group of microorganisms only distantly related to the Proteobacteria, chlamydial outer membrane proteins pose an even greater challenge to prediction programs than proteins from organisms more closely related to the training set
The last step aimed at the identification of integral outer membrane proteins and outer membrane lipoproteins within this subset based on conserved structural features
Summary
Chlamydiae are obligate intracellular bacteria comprising some of the most important bacterial pathogens of animals and humans. Multiphasic in silico approach, including the calculation of clusters of orthologues, to predict outer membrane proteins using conservative criteria. We tested this approach using Escherichia coli (positive control) and Bacillus subtilis (negative control), and applied it to five chlamydial species; Chlamydia trachomatis, Chlamydia muridarum, Chlamydia (a.k.a. Chlamydophila) pneumoniae, Chlamydia (a.k.a. Chlamydophila) caviae, and Protochlamydia amoebophila. The phylum Chlamydiae is a unique group of evolutionary well separated, intracellular bacteria that comprises some of the most important bacterial pathogens of humans and animals. Evidence exists that the recognized diversity and host range represent only the tip of the iceberg and that chlamydiae are ubiquitous [6]
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