Characterization of a hypervariable region in the genome of Chlamydophila pneumoniae

Chlamydophila pneumoniae displays surprisingly little genomic variation, as seen by comparisons of the published genomes from three different isolates and sequencing of four different genes from different isolates. We have in the present study, however, demonstrated genomic variation between 10 C pn eumoniae isolates in the 11 690-bp region between the two outer membrane pr otein genes pmp1 and pmp2. This region of the C pneumoniae CWL-029 isolate contains seven C. pneumoniae-specific open reading frames (hbl-7, encoding hydrophobic beta-sheet-containing proteins). We identified additionally 12 open reading frames in the C. pneumoniae CWL-029 genome encoding hypothetic al proteins with similarity to the seven hypothetical Hb-proteins. Compared to other isolates, genomic variation is seen to cause frame-shifting of th ree of the 19 hh-open reading frames. which are proposed to be three full-l ength genes and eight frame-shifted pseudogenes. The hypothetical proteins encoded by these proposed genes contain an N-terminally located highly hydr ophobic stretch of 50-60 residues. A similar motif is found in all identifi ed Chlamydia inclusion membrane proteins and therefore the Hb-proteins are candidate inclusion proteins. (C) 2001 Federation of European Microbiologic al Societies. Published by Elsevier Science B.V. All rights reserved.