Chlamydiaceae is a family of bacteria that belongs to the Phylum Chlamydiae

Chlamydiae

Chlamydiae is a bacterial phylum and class whose members are obligate intracellular pathogens. Many Chlamydiae coexist in an asymptomatic state within specific hosts, and it is widely believed that these hosts provide a natural reservoir for these species....

, Order Chlamydiales

Chlamydiales

The bacterial order Chlamydiales includes only obligately intracellular bacteria that have a chlamydia-like developmental cycle of replication and at least 80% 16S rRNA or 23S rRNA gene sequence identity with other members of Chlamydiales. Chlamydiales live in animals, insects, and protozoa...

. All Chlamydiaceae species are Gram-negative and express the family-specific lipopolysaccharide epitope

Epitope

An epitope, also known as antigenic determinant, is the part of an antigen that is recognized by the immune system, specifically by antibodies, B cells, or T cells. The part of an antibody that recognizes the epitope is called a paratope...

 αKdo-(2→8)-αKdo-(2→4)-αKdo (previously called the genus-specific epitope). Chlamydiaceae ribosomal RNA

RNA

Ribonucleic acid , or RNA, is one of the three major macromolecules that are essential for all known forms of life....

 genes all have at least 90% DNA

DNA

Deoxyribonucleic acid is a nucleic acid that contains the genetic instructions used in the development and functioning of all known living organisms . The DNA segments that carry this genetic information are called genes, but other DNA sequences have structural purposes, or are involved in...

 sequence identity. Chlamydiaceae species have varying inclusion morphology, varying extrachromosomal plasmid

Plasmid

In microbiology and genetics, a plasmid is a DNA molecule that is separate from, and can replicate independently of, the chromosomal DNA. They are double-stranded and, in many cases, circular...

 content, and varying sulfadiazine resistance.

Chlamydiaceae currently includes two genera and one candidate genus: Chlamydia

Chlamydia

Chlamydia infection is a common sexually transmitted infection in humans caused by the bacterium Chlamydia trachomatis. The term Chlamydia infection can also refer to infection caused by any species belonging to the bacterial family Chlamydiaceae. C. trachomatis is found only in humans...

, Chlamydophila

Chlamydophila

Chlamydophila is a bacterial genus belonging to the family Chlamydiaceae, order Chlamydiales, class/phylum Chlamydiae.-Taxonomy:Chlamydophila was recognized in 1999, with six species in Chlamydophila and three in the original genus, Chlamydia...

and Candidatus Clavochlamydia.

Chlamydia

Three species belong to Chlamydia: C. trachomatis

Chlamydia trachomatis

Chlamydia trachomatis, an obligate intracellular human pathogen, is one of three bacterial species in the genus Chlamydia. C. trachomatis is a Gram-negative bacteria, therefore its cell wall components retain the counter-stain safranin and appear pink under a light microscope.The inclusion bodies...

, C. muridarum

Chlamydia muridarum

Chlamydia muridarum is an intracellular bacterial species that at one time belonged to Chlamydia trachomatis. However, C. trachomatis naturally only infects humans and C...

, and C. suis

Chlamydia suis

Chlamydia suis is a member of the genus Chlamydia. C. suis has only been isolated from swine, in which it may be endemic. Glycogen has been detected in Chlamydia suis inclusions in infected swine tissues and in cell culture. C...

. C. trachomatis has been found only in humans, C. muridarum in hamsters and mice (family Muridae

Muridae

Muridae is the largest family of mammals. It contains over 600 species found naturally throughout Eurasia, Africa, and Australia. They have been introduced worldwide. The group includes true mice and rats, gerbils, and relatives....

), and C. suis in swine. Chlamydia

Chlamydia (bacterium)

Chlamydia is a genus of bacteria that are obligate intracellular parasites. Chlamydia infections are the most common bacterial sexually transmitted infections in humans and are the leading cause of infectious blindness worldwide....

 spp. produce a small amount of detectable glycogen

Glycogen

Glycogen is a molecule that serves as the secondary long-term energy storage in animal and fungal cells, with the primary energy stores being held in adipose tissue...

 and have two ribosomal operon

Operon

In genetics, an operon is a functioning unit of genomic DNA containing a cluster of genes under the control of a single regulatory signal or promoter. The genes are transcribed together into an mRNA strand and either translated together in the cytoplasm, or undergo trans-splicing to create...

s.

C. trachomatis

Chlamydia trachomatis

Chlamydia trachomatis, an obligate intracellular human pathogen, is one of three bacterial species in the genus Chlamydia. C. trachomatis is a Gram-negative bacteria, therefore its cell wall components retain the counter-stain safranin and appear pink under a light microscope.The inclusion bodies...

 is the cause of a Chlamydia infection commonly transmitted sexually

Sexually transmitted disease

Sexually transmitted disease , also known as a sexually transmitted infection or venereal disease , is an illness that has a significant probability of transmission between humans by means of human sexual behavior, including vaginal intercourse, oral sex, and anal sex...

 (often referred as just "Chlamydia") and also causes trachoma

Trachoma

Trachoma is an infectious disease causing a characteristic roughening of the inner surface of the eyelids. Also called granular conjunctivitis and Egyptian ophthalmia, it is the leading cause of infectious blindness in the world...

, an infectious eye disease, spread by eye, nose, and throat secretions.

Chlamydophila

Six species belong to Chlamydophila: C. pneumoniae

Chlamydophila pneumoniae

Chlamydophila pneumoniae is a species of Chlamydophila, an obligate intracellular bacteria that infects humans and is a major cause of pneumonia....

 (often also called Chlamydia pneumoniae), C. pecorum

Chlamydophila pecorum

Chlamydophila pecorum is a species of Chlamydiaceae that has been isolated only from mammals: cattle, sheep and goats , koalas , and swine. C. pecorum strains are serologically and pathogenically diverse....

, C. psittaci

Chlamydophila psittaci

Chlamydophila psittaci is a lethal intracellular bacterial species that may cause endemic avian chlamydiosis, epizootic outbreaks in mammals, and respiratory psittacosis in humans. Chlamydophila psittaci is transmitted by inhalation, contact or ingestion among birds and to mammals...

, C. abortus

Chlamydophila abortus

Chlamydophila abortus is a species in Chlamydiae that causes abortion and fetal death in mammals, including humans. Chlamydophila abortus was previously classified as Chlamydia psittaci along with all Chlamydiae except Chlamydia trachomatis. This was based on a lack of evident glycogen production...

, C. caviae

Chlamydophila caviae

Chlamydophila caviae is a bacterium that can be recovered from the conjunctiva of Guinea pigs suffering from ocular inflammation and eye discharge. It is also possible to infect the genital tract of Guinea pigs with C. caviae and elicit a disease that is very similar to human Chlamydia trachomatis...

, and C. felis

Chlamydophila felis

Chlamydophila felis is a bacterium endemic among house cats worldwide, primarily causing inflammation of feline conjunctiva, rhinitis and respiratory problems. C. felis can be recovered from the stomach and reproductive tract. Zoonotic infection of humans with C. felis has been reported...

. Chlamydophila

Chlamydophila

Chlamydophila is a bacterial genus belonging to the family Chlamydiaceae, order Chlamydiales, class/phylum Chlamydiae.-Taxonomy:Chlamydophila was recognized in 1999, with six species in Chlamydophila and three in the original genus, Chlamydia...

 spp. do not produce detectable glycogen

Glycogen

Glycogen is a molecule that serves as the secondary long-term energy storage in animal and fungal cells, with the primary energy stores being held in adipose tissue...

 and have one ribosomal operon. These species are naturally found living in a variety of animals.