Related Experiment Videos
Remarkable sequence relatedness in the DNA encoding the major outer membrane protein of Chlamydia psittaci (koala
A A Girjes1, F N Carrick, M F Lavin
1Queensland Cancer Fund Research Unit, Queensland Institute of Medical Research, Brisbane, Australia.
Abstract:
DNA encoding the major outer membrane protein (MOMP) of the koala type-I strain of Chlamydia psittaci (pathogen responsible for blindness and infertility in koalas) was cloned and sequenced. Comparison with momp gene sequences from other chlamydial species revealed a remarkable degree of homology (> 97%) with that of the human pathogen, Chlamydia pneumoniae. In comparison, the sequence only shared 75% DNA sequence homology with other C. psittaci members and 69% homology with C. trachomatis. The open reading frame consisted of 1167 bp encoding a 389-amino acid (aa) pre-MOMP including a leader sequence of 23 aa, similar to the C. pneumoniae gene. These genes were closely related even within the four variable domains (86-100% homology). Specific antibodies were capable of distinguishing between koala type I and C. pneumoniae. This very high degree of relatedness between C. pneumoniae, a human pathogen, and an individual strain of C. psittaci in the momp gene raises further questions on the host specificity, classification and evolutionary relationships of the different chlamydial species.
Insights
The koala Chlamydia psittaci major outer membrane protein (MOMP) gene shows over 97% homology with the human pathogen Chlamydia pneumoniae, challenging chlamydial host specificity and classification. This finding prompts further research into chlamydial evolutionary relationships.
Area of Science:
- Microbiology
- Genetics
- Veterinary Medicine
Background:
- Chlamydia psittaci causes blindness and infertility in koalas.
- The major outer membrane protein (MOMP) is a key surface antigen in Chlamydia species.
- Understanding genetic relatedness is crucial for Chlamydia classification and host specificity.
Purpose of the Study:
- To clone and sequence the MOMP gene from a koala C. psittaci strain.
- To compare the koala C. psittaci MOMP gene sequence with those of other Chlamydia species.
- To investigate the evolutionary relationships and host specificity of Chlamydia species based on MOMP gene homology.
Main Methods:
- DNA cloning and sequencing of the koala C. psittaci MOMP gene.
- Bioinformatic analysis and comparison of MOMP gene sequences from various Chlamydia species.
- Antibody-based assays to differentiate between koala C. psittaci and C. pneumoniae.
Main Results:
- The koala C. psittaci MOMP gene sequence exhibited >97% DNA homology with C. pneumoniae, but only 75% with other C. psittaci strains and 69% with C. trachomatis.
- The deduced amino acid sequence of pre-MOMP was similar to that of C. pneumoniae, including conserved variable domains.
- Specific antibodies could differentiate between the koala strain and C. pneumoniae.
Conclusions:
- A high degree of MOMP gene relatedness exists between a koala C. psittaci strain and the human pathogen C. pneumoniae.
- This finding raises questions regarding the host specificity, classification, and evolutionary history of Chlamydia species.
- Further research is warranted to elucidate the complex relationships within the Chlamydia genus.