Research article

Intrastrain and interstrain genetic variation within a paralogous gene family in Chlamydia pneumoniae

Wasna Viratyosin^1,3 , Lee Ann Campbell² , Cho-Chou Kuo² and Daniel D Rockey¹

¹Department of Microbiology, Oregon State University, Corvallis, 97331-3804, USA

²Department of Pathobiology, University of Washington, Seattle, 98195, USA

³Present Address: National Center for Genetic Engineering and Biotechnology, 113 Paholyothin Rd., Klong 1, Klong Luang, Pathumthani 12120, Thailand

author email corresponding author email

BMC Microbiology 2002, 2:38doi:10.1186/1471-2180-2-38

Published:	2 December 2002

Abstract

Background

Chlamydia pneumoniae causes human respiratory diseases and has recently been associated with atherosclerosis. Analysis of the three recently published C. pneumoniae genomes has led to the identification of a new gene family (the Cpn 1054 family) that consists of 11 predicted genes and gene fragments. Each member encodes a polypeptide with a hydrophobic domain characteristic of proteins localized to the inclusion membrane.

Results

Comparative analysis of this gene family within the published genome sequences provided evidence that multiple levels of genetic variation are evident within this single collection of paralogous genes. Frameshift mutations are found that result in both truncated gene products and pseudogenes that vary among isolates. Several genes in this family contain polycytosine (polyC) tracts either upstream or within the terminal 5' end of the predicted coding sequence. The length of the polyC stretch varies between paralogous genes and within single genes in the three genomes. Sequence analysis of genomic DNA from a collection of 12 C. pneumoniae clinical isolates was used to determine the extent of the variation in the Cpn 1054 gene family.

Conclusions

These studies demonstrate that sequence variability is present both among strains and within strains at several of the loci. In particular, changes in the length of the polyC tract associated with the different Cpn 1054 gene family members are common within each tested C. pneumoniae isolate. The variability identified within this newly described gene family may modulate either phase or antigenic variation and subsequent physiologic diversity within a C. pneumoniae population.