Gram-negative-type cell wall but no peptidoglycan.
Smaller than most bacteria.
Constitute an important group of pathogens responsible for acute and chronic diseases of humans and are also of veterinary importance. C. trachomatis and C. pneumoniae are the primary species pathogenic for humans.
Obligate intracellular pathogens.
Like Salmonella and Shigella, chlamydiae use the activity of small GTPases of the Rho family to transiently remodel the actin cytoskeleton and invade eukaryotic cells.
All species share a unique developmental cycle during multiplication in a vacuole, called an inclusion, within a host cell. The infectious form of the developmental cycle, called the elementary body (EB), is small (about 0.3μm in diameter) and essentially metabolically inactive. After entering epithelial host cells, EBs differentiate within a few hours into larger (about 1μm), more pleomorphic, reticulate bodies (RBs). RBs are metabolically active, noninfectious, and represent the replicating form.
C. trachomatis strains are the most common cause of bacterial sexually transmitted disease. Sequelae in women include pelvic inflammatory disease, ectopic pregnancy and sterility. A subset of C. trachomatis strains cause trachoma, a leading cause of preventable blindness in the developing world.
C. pneumoniae is estimated to be responsible for about 10% of community-acquired pneumonia and 5% of bronchitis and sinusitis cases in adults. Furthermore, C. pneumoniae is of intense interest because chronic infection with this pathogen might contribute to cardiovascular disease.
Selected genomes: ⇒ comparative pathogenomics ⇐
C. muridarum Nigg, 1072950 bp, NC_002620
C. trachomatis 434/Bu, 1038842 bp, NC_010287
C. trachomatis A/HAR-13, 1044459 bp, NC_007429
C. trachomatis D/UW-3/CX, 1042519 bp, NC_000117
C. trachomatis L2b/UCH-1/proctitis, 1038869 bp, NC_010280
C. abortus S26/3, 1144377 bp, NC_004552
C. caviae GPIC, 1173390 bp, NC_003361
C. felis Fe/C-56, 1166239 bp, NC_007899
C. pneumoniae AR39, 1229853 bp, NC_002179
C. pneumoniae CWL029, 1230230 bp, NC_000922
C. pneumoniae J138, 1226565 bp, NC_002491
C. pneumoniae TW-183, 1225935 bp, NC_005043
Stephens RS, et al., 1998. Genome sequence of an obligate intracellular pathogen of humans: Chlamydia trachomatis. Science 282(5389):754-759.
Kalman S, et al., 1999. Comparative genomes of Chlamydia pneumoniae and C. trachomatis Nat. Genet. 21(4):385-389.
Read TD, et al., 2000. Genome sequences of Chlamydia trachomatis MoPn and Chlamydia pneumoniae AR39. Nucleic Acids Res. 28(6):1397-1406.
Shirai M, et al., 2000. Comparison of whole genome sequences of Chlamydia pneumoniae J138 from Japan and CWL029 from USA. Nucleic Acids Res. 28(12):2311-2314.
Read TD, et al., 2003. Genome sequence of Chlamydophila caviae (Chlamydia psittaci GPIC): examining the role of niche-specific genes in the evolution of the Chlamydiaceae. Nucleic Acids Res. 31(8):2134-2147.
Thomson NR, et al., 2005. The Chlamydophila abortus genome sequence reveals an array of variable proteins that contribute to interspecies variation. Genome Res. 15(5):629-640.
Carlson JH, et al., 2005. Comparative genomic analysis of Chlamydia trachomatis oculotropic and genitotropic strains. Infect. Immun. 73(10):6407-6418.
Azuma Y, et al., 2006. Genome sequence of the cat pathogen, Chlamydophila felis. DNA Res. 13(1):15-23.
Thomson NR, et al., 2008. Chlamydia trachomatis: genome sequence analysis of lymphogranuloma venereum isolates. Genome Res 18(1):161-171.
The life cycle of Chlamydia trachomatis (From: Elwell C, et al., 2016. Chlamydia cell biology and pathogenesis. Nat Rev Microbiol 14:385-400.).
Major virulence factors in Chlamydia:
Genomic location of virulence-related genes in Chlamydia:
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