Related Experiment Videos
Microvirus of chlamydia psittaci strain guinea pig inclusion conjunctivitis: isolation and molecular characterization
Ru-Ching Hsia1, Li-Min Ting2, Patrik M Bavoil1
1Department of Infectious and Tropical Diseases, London School of Hygiene & Tropical Medicine, London WC1E 7HT, UK1.
Abstract:
The authors report the isolation and molecular characterization of a bacteriophage, φCPG1, which infects CHLAMYDIA: psittaci strain Guinea pig Inclusion Conjunctivitis. Purified virion preparations contained isometric particles of 25 nm diameter, superficially similar to spike-less members of the φX174 family of bacteriophages. The single-stranded circular DNA genome of φCPG1 included five large ORFs, which were similar to ORFs in the genome of a previously described CHLAMYDIA: bacteriophage (Chp1) that infects avian C. psittaci. Three of the ORFs encoded polypeptides that were similar to those in a phage infecting the mollicute Spiroplasma melliferum, a pathogen of honeybees. Lesser sequence similarities were seen between two ORF products and the major capsid protein of the φX174 coliphage family and proteins mediating rolling circle replication initiation in phages, phagemids and plasmids. Phage φCPG1 is the second member of the genus CHLAMYDIAMICROVIRUS:, the first to infect a member of a CHLAMYDIA: species infecting mammals. Similarity searches of the nucleotide sequence further revealed a highly conserved (75% identity) 375 base sequence integrated into the genome of the human pathogen Chlamydia pneumoniae. This genomic segment encodes a truncated 113 residue polypeptide, the sequence of which is 72% identical to the amino-terminal end of the putative replication initiation protein of φCPG1. This finding suggests that C. pneumoniae has been infected by a phage related to φCPG1 and that infection resulted in integration of some of the phage genome into the C. pneumoniae genome.
Insights
Researchers isolated bacteriophage φCPG1, the first of its kind infecting mammalian Chlamydia psittaci. Its genome shows similarities to other phages, and a related sequence is integrated into the human pathogen Chlamydia pneumoniae.
Area of Science:
- Microbiology
- Virology
- Genomics
Background:
- Bacteriophages are viruses that infect bacteria.
- Chlamydia psittaci is a bacterium that can infect mammals and birds.
- Previous research has identified bacteriophages infecting Chlamydia species.
Purpose of the Study:
- To isolate and characterize a novel bacteriophage infecting Chlamydia psittaci.
- To investigate the genomic similarities between bacteriophages infecting Chlamydia species.
- To explore potential phage integration events in pathogenic Chlamydia.
Main Methods:
- Isolation and purification of bacteriophage virions.
- Electron microscopy for particle morphology.
- Genome sequencing and open reading frame (ORF) analysis.
- Sequence similarity searches against public databases.
Main Results:
- Isolation of bacteriophage φCPG1, infecting Chlamydia psittaci strain Guinea pig Inclusion Conjunctivitis.
- φCPG1 possesses isometric particles (25 nm) and a single-stranded circular DNA genome with five ORFs.
- Genomic sequences show similarities to Chlamydia bacteriophage Chp1 and phages infecting Spiroplasma melliferum.
- A conserved 375-base sequence, 75% identical to a φCPG1 gene, was found integrated in the Chlamydia pneumoniae genome.
Conclusions:
- φCPG1 is the first described bacteriophage in the genus Chlamydiamicrovirus to infect a mammalian Chlamydia species.
- Genomic similarities suggest evolutionary relationships among Chlamydia-infecting phages.
- The integrated sequence in Chlamydia pneumoniae indicates a past infection by a φCPG1-related phage.