| Chlamydophila | |
|---|---|
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| Chlamydophila psittaci | |
Scientific classification  | |
| Domain: | Bacteria |
| Phylum: | Chlamydiota |
| Class: | Chlamydiia |
| Order: | Chlamydiales |
| Family: | Chlamydiaceae |
| Genus: | Chlamydophila Everett, Bush & Andersen 1999 |
| Type species | |
| Chlamydophila psittaci (Lillie 1930) Everett, Bush & Andersen 1999 | |
| Species [1] | |
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| Synonyms | |
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Chlamydophila is a controversial bacterial genus belonging to the family Chlamydiaceae. [2]
All Chlamydiota are anaerobic bacteria with a biphasic developmental lifecycle that depends on obligately intracellular growth in eukaryotic host cells.
Chlamydophila was recognized by a number of scientists in 1999, [3] with six species in Chlamydophila and three in the original genus, Chlamydia . This was immediately seen as controversial. [4] In 2015 the Chlamydophila species were reclassified as Chlamydia. [4] The history of the classification and reclassification is as follows.
Earlier criteria for differentiation of chlamydial species did not always work well. For example, at that time genus C. psittaci was distinguished from C. trachomatis by sulfadiazine resistance, although not all strains identified as C. psittaci at the time were resistant, and C. pneumoniae was classified by its appearance under electron microscopy (EM) and its ability to infect humans, although the EM appearance may differ from one research group to the next, and many of these species infected humans.
The systematic taxonomy established for Chlamydiota (formerly Chlamydiae) in 1999 used DNA-DNA reassociation, 16S and 23S ribosomal RNA gene similarity, sequence similarity clustering of protein coding genes, and genome size as criteria for classification. Supporting criteria such as antigen detection, [5] glycogen staining, host association, and EM morphology were also employed, depending on applicability and availability.
Comparative genomic analyses in 2006 identified a number of signature proteins that were uniquely present in species from the genera Chlamydia and Chlamydophila, which supported the distinctness of Chlamydophila. [6] This view was challenged three years later by newer whole genome analysis techniques leading to a proposal to "reunite the Chlamydiaceae into a single genus, Chlamydia". [7] By the 2010s this reclassification "was not wholly accepted or adopted" [8] among microbiologists, which "resulted in a reversion to the single, original genus Chlamydia, which now encompasses all 9 species including Chlamydia psittaci." [8] As of 2013, Chlamydophila was still mentioned in some databases, but controversial. [9] The merger of the genus Chlamydophila back into the genus Chlamydia is now generally accepted. [10] [11] [12] [13]
According to the authors of the 1999 study, the mean DNA–DNA reassociation difference distinguishing Chlamydophila from Chlamydia is 10.1%, an accepted value for genus separation. Although the 16S ribosomal RNA gene sequences of the two are close to 95% identical, unlike the other previously established genera, the authors considered a less than 95% similarity only a guideline for establishing new genera in chlamydial families. In the study, the authors used the similarity of the locations of coding for protein and ribosomal RNA genes in the genome (gene clusters) to help distinguish Chlamydophila from Chlamydia. Also, the full-length 23S ribosomal RNA genes of the species of the two genera were less than 95% identical.
| Genus | Approximate Genome Size (million DNA base pairs) | Detectable Glycogen | Number of Ribosomal Operons |
|---|---|---|---|
| Chlamydophila | 1.2 | No | 1 |
| Chlamydia | 1.0 | Yes | 2 |
| 16S rRNA based LTP_08_2023 [14] [15] [16] | 120 marker proteins based GTDB 08-RS214 [17] [18] [19] | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
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The Korarchaeota is a proposed phylum within the Archaea. The name is derived from the Greek noun koros or kore, meaning young man or young woman, and the Greek adjective archaios which means ancient. They are also known as Xenarchaeota. The name is equivalent to Candidatus Korarchaeota, and they go by the name Xenarchaeota or Xenarchaea as well.
Chlamydia trachomatis is a Gram-negative, anaerobic bacterium responsible for chlamydia and trachoma. C. trachomatis exists in two forms, an extracellular infectious elementary body (EB) and an intracellular non-infectious reticulate body (RB). The EB attaches to host cells and enter the cell using effector proteins, where it transforms into the metabolically active RB. Inside the cell, RB's rapidly replicate before transitioning back to EB's, which are then released to infect new host cells.
The Chlamydiota are a bacterial phylum and class whose members are remarkably diverse, including pathogens of humans and animals, symbionts of ubiquitous protozoa, and marine sediment forms not yet well understood. All of the Chlamydiota that humans have known about for many decades are obligate intracellular bacteria; in 2020 many additional Chlamydiota were discovered in ocean-floor environments, and it is not yet known whether they all have hosts. Historically it was believed that all Chlamydiota had a peptidoglycan-free cell wall, but studies in the 2010s demonstrated a detectable presence of peptidoglycan, as well as other important proteins.
Chlamydia psittaci is a lethal intracellular bacterial species that may cause endemic avian chlamydiosis, epizootic outbreaks in other mammals, and respiratory psittacosis in humans. Potential hosts include feral birds and domesticated poultry, as well as cattle, pigs, sheep, and horses. C. psittaci is transmitted by inhalation, contact, or ingestion among birds and to mammals. Psittacosis in birds and in humans often starts with flu-like symptoms and becomes a life-threatening pneumonia. Many strains remain quiescent in birds until activated by stress. Birds are excellent, highly mobile vectors for the distribution of chlamydia infection, because they feed on, and have access to, the detritus of infected animals of all sorts.
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.
Chlorobium is a genus of green sulfur bacteria. They are photolithotrophic oxidizers of sulfur and most notably utilise a noncyclic electron transport chain to reduce NAD+. Photosynthesis is achieved using a Type 1 Reaction Centre using bacteriochlorophyll (BChl) a. Two photosynthetic antenna complexes aid in light absorption: the Fenna-Matthews-Olson complex, and the chlorosomes which employ mostly BChl c, d, or e. Hydrogen sulfide is used as an electron source and carbon dioxide its carbon source.
The Chlamydiaceae are a family of gram-negative bacteria that belongs to the phylum Chlamydiota, order Chlamydiales. Chlamydiaceae species express the family-specific lipopolysaccharide epitope αKdo-(2→8)-αKdo-(2→4)-αKdo. Chlamydiaceae ribosomal RNA genes all have at least 90% DNA sequence identity. Chlamydiaceae species have varying inclusion morphology, varying extrachromosomal plasmid content, and varying sulfadiazine resistance.
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. suis is associated with conjunctivitis, enteritis and pneumonia in swine.
Parachlamydiaceae is a family of bacteria in the order Chlamydiales. Species in this family have a Chlamydia–like cycle of replication and their ribosomal RNA genes are 80–90% identical to ribosomal genes in the Chlamydiaceae. The Parachlamydiaceae naturally infect amoebae and can be grown in cultured Vero cells. The Parachlamydiaceae are not recognized by monoclonal antibodies that detect Chlamydiaceae lipopolysaccharide.
Simkaniaceae is a family of bacteria in the order Chlamydiales, class Chlamydiia, phylum Chlamydiota, domain Bacteria. Species in this family have a chlamydia-like cycle of replication and their ribosomal RNA genes are 80–90% identical to ribosomal genes in the Chlamydiaceae. The Simkaniaceae are not recognized by monoclonal antibodies that are specific for Chlamydiaceae lipopolysaccharide. The family Simkaniaceae currently includes two genera: Simkania and Fritschea. The type species is Simkania negevensis, and its natural host is not known. It is readily grown in monolayers of eukaryotic Vero cells. Serological evidence and PCR indicate that S. negevensis is widespread among humans.
Chlamydia abortus is a species in Chlamydiota that causes abortion and fetal death in mammals, including humans. Chlamydia abortus was renamed in 1999 as Chlamydophila psittaci along with all Chlamydiota except Chlamydia trachomatis. This was based on a lack of evident glycogen production and on resistance to the antibiotic sulfadiazine. In 1999 C. psittaci and C. abortus were recognized as distinct species based on differences of pathogenicity and DNA–DNA hybridization. In 2015, this new name was reverted to Chlamydia.
Chlamydia felis is a Gram-negative, obligate intracellular bacterial pathogen that infects cats. It is endemic among domestic 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. Strains FP Pring and FP Cello have an extrachromosomal plasmid, whereas the FP Baker strain does not. FP Cello produces lethal disease in mice, whereas the FP Baker does not. An attenuated FP Baker strain, and an attenuated 905 strain, are used as live vaccines for cats.
Chlamydia 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 infection. C. caviae infects primarily the mucosal epithelium and is not invasive.
Chlamydia pecorum, also known as Chlamydophila pecorum is a species of Chlamydiaceae that originated from ruminants, such as cattle, sheep and goats. It has also infected koalas and swine. C. pecorum strains are serologically and pathogenically diverse.
Chlamydia is a genus of pathogenic Gram-negative bacteria that are obligate intracellular parasites. Chlamydia infections are the most common bacterial sexually transmitted diseases in humans and are the leading cause of infectious blindness worldwide.
16S ribosomal RNA is the RNA component of the 30S subunit of a prokaryotic ribosome. It binds to the Shine-Dalgarno sequence and provides most of the SSU structure.
Parachlamydia acanthamoebae are bacterium that fall into the category of host-associated microorganisms. This bacterium lives within free-living amoebae that are an intricate part of their reproduction. Originally named Candidatus Parachlamydia acanthamoebae, its current scientific name was introduced shortly after. This species has shown to have over eighty percent 16S rRNA gene sequencing identity with the class Chlamydiia. Parachlamydia acanthamoebae has the same family as the genus Neochlamydia with which it shares many similarities.
Caldibacillus is a facultative anaerobe genus of bacteria that stains Gram-positive from the family of Bacillaceae. The type species of this genus is Caldibacillus debilis.
Natrialbales is an order of halophilic, chemoorganotrophic archaea within the class Haloarchaea. The type genus of this order is Natrialba.
Haloferacales is an order of halophilic, chemoorganotrophic or heterotrophic archaea within the class Haloarchaea. The type genus of this order is Haloferax.
Given the contentious nature of the issue, the NCBI Taxonomy Database retains both genus names for use by submitters.
| Authority control databases: National |
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