Instruct: Given a question, retrieve relevant passages that can help answer the question.
Query: What is a phylum?
In biology, a phylum (/ˈfaɪləm/; plural: phyla) is a level of classification or taxonomic rank below Kingdom and above Class. Traditionally, in botany the term division has been used instead of phylum, although the International Code of Nomenclature for algae, fungi, and plants accepts the terms as equivalent.[1][2][3] Depending on definitions, the animal kingdom Animalia or Metazoa contains approximately 35 phyla, the plant kingdom Plantae contains about 14, and the fungus kingdom Fungi contains about 8 phyla. Current research in phylogenetics is uncovering the relationships between phyla, which are contained in larger clades, like Ecdysozoa and Embryophyta.
Currently, the phylum contains only one family, Salterellidae; a second family, Volborthellidae, was originally included but later became a synonym of the former. No orders, classes or superfamilies are used within the phylum, despite the order "Volborthellida" being previously proposed for "Volborthella" before the phylum's own proposal. The reasoning for this was that taxa of these ranks were not seen as necessary in a phylum with very few genera.
Neocallimastigomycota is a phylum containing anaerobic fungi, which are symbionts found in the digestive tracts of larger herbivores. Anaerobic fungi were originally placed within phylum Chytridiomycota, within Order Neocallimastigales but later raised to phylum level, a decision upheld by later phylogenetic reconstructions. It encompasses only one family.
The FCB group (now called Sphingobacteria) includes Bacteroidetes, the unplaced genus "Caldithrix", Chlorobi, candidate phylum Cloacimonetes, Fibrobacteres, Gemmatimonadates, candidate phylum Ignavibacteriae, candidate phylum Latescibacteria, candidate phylum Marinimicrobia, and candidate phylum Zixibacteria.
Historically, all fungi producing a zygospore were considered to be related and placed into Zygomycota. The use of molecular phylogenetics has increasingly revealed this grouping to be paraphyletic. However, the rank (i.e., phylum or subphylum) these clades is in dispute. What follows is a phylogeny of fungi with the zygomycete subphyla derived from Spatafora et al. (2016) with both possible phylum names.
New species have been cultured since 1987, when Woese's review paper was published, that are sufficiently different that they warrant a new phylum. Most of these are thermophiles and often also chemolithoautotrophs, such as Aquificae, which oxidises hydrogen gas. Other non-thermophiles, such as Acidobacteria, a ubiquitous phylum with divergent physiologies, have been found, some of which are chemolithotrophs, such as "Nitrospira" (nitrile-oxidising) or "Leptospirillum" (Fe-oxidising)., some proposed phyla however do not appear in LPSN as they were insufficiently described or are awaiting approval or it is debated if they may belong to a pre-existing phylum. An example of this is the genus "Caldithrix", consisting of "C. palaeochoryensis" and "C. abyssi", which is considered Deferribacteres, however, it shares only 81% similarity with the other Deferribacteres ("Deferribacter" species and relatives) and is considered a separate phylum by Rappé and Giovannoni. Additionally the placement of the genus "Geovibrio" in the phylum Deferribacteres is debated.
Verrucomicrobia is a phylum of bacteria. This phylum contains only a few described species ("Verrucomicrobium spinosum", is an example, the phylum is named after this). The species identified have been isolated from fresh water and soil environments and human faeces. A number of as-yet uncultivated species have been identified in association with eukaryotic hosts including extrusive explosive ectosymbionts of protists and endosymbionts of nematodes residing in their gametes. While verrucae is another name for the warts often found on hands and feet, this phylum is so called not because it is a causative agent thereof, but because of its wart-like morphology.
Comparative genomic analysis has led to the identification of 2 conserved signature indels which are uniquely found in members of the phylum "Chlorobi" and are thus characteristic of the phylum. The first indel is a 28-amino-acid insertion in DNA polymerase III and the second is a 12 to 14 amino acid insertion in alanyl-tRNA synthetase. These indels are not found in any other bacteria and thus serve as molecular markers for the phylum. In addition to the conserved signature indels, 51 proteins which are uniquely found in members of the phylum "Chlorobi". 65 other proteins have been identified which are unique to the "Chlorobi" phylum, however these proteins are missing in several "Chlorobi" species and are not distributed throughout the phylum with any clear pattern. This means that significant gene loss may have occurred, or the presence of these proteins may be a result of horizontal gene transfer. Of these 65 proteins, 8 are found only in "Chlorobium luteolum" and "Chlorobium phaeovibrioides". These two species form a strongly supported clade in phylogenetic trees and a close relationship between these species is further supported by the unique sharing of these 8 proteins.
There is no doubt that the phylum Nemertea is monophyletic (meaning that the phylum includes all and only descendants of one ancestor that was also a member of the phylum). The synapomorphies (trait shared by an ancestor and all its descendants, but not by other groups) include the eversible proboscis located in the rhynchocoel.
This section lists the orders of Bacteria within the phylum Bacteroidetes.
This section lists the orders of Bacteria within the phylum Chlamydiae.This section lists the orders of Bacteria within the phylum Chlorobi.
This section lists the orders of Bacteria within the phylum Chloroflexi.
This section lists the orders of Bacteria within the phylum Chrysiogenetes.This section lists the orders of Bacteria within the phylum Cyanobacteria.
This section lists the orders of Bacteria within the phylum Deferribacteres.This section lists the orders of Bacteria within the phylum Deinococcus-Thermus.This section lists the orders of Bacteria within the phylum Dictyoglomi.This section lists the orders of Bacteria within the phylum Elusimicrobia.
Since then a candidate phylum called Poribacteria was discovered, living in symbiosis with sponges and extensively studied. (Note: the divergence of the major bacterial lineages predates sponges) Another candidate phylum, called Tectomicrobia, was also found living in symbiosis with sponges. And "Nitrospina gracilis", which had long eluded phylogenetic placement, was proposed to belong to a new phylum, Nitrospinae.
Recent phylogenetic analysis of the Chloroflexi has found very weak support for the grouping together of the different classes currently part of the phylum. The six classes that make up the phylum did not consistently form a well-supported clade in phylogenetic trees based on concatenated sequences for large datasets of proteins and no conserved signature indels were identified that were uniquely shared by the entire phylum. However, the classes "Chloroflexi" and Thermomicrobia were found to group together consistently by both the usual phylogenetic means and the identification of shared conserved signature indels in the 50S ribosomal protein L19 and the enzyme UDP-glucose 4-epimerase. It has been suggested that the phylum Chloroflexi ""sensu stricto"" should comprise only the classes Chloroflexi and Thermomicrobia, and the other four classes ("Dehalococcoidetes," Anaerolineae, Caldilineae and Ktedonobacteria) may represent one or more independent phyla branching in the neighborhood of the Chloroflexi.
The approach is useful because it makes it easy to classify extinct organisms as "stem groups" to the phyla with which they bear the most resemblance, based only on the taxonomically important similarities.[8] However, proving that a fossil belongs to the crown group of a phylum is difficult, as it must display a character unique to a sub-set of the crown group.[8] Furthermore, organisms in the stem group of a phylum can possess the "body plan" of the phylum without all the characteristics necessary to fall within it. This weakens the idea that each of the phyla represents a distinct body plan.[11]
Several candidate phyla (Microgenomates, Omnitrophica, Parcubacteria, and Saccharibacteria) and several accepted phyla (Elusimicrobia, Caldiserica, and Armatimonadetes) have been suggested to actually be superphyla that were incorrectly described as phyla because rules for defining a bacterial phylum are lacking. For example, it is suggested that candidate phylum Microgenomates is actually a superphylum that encompasses 28 subordinate phyla and that phylum Elusimocrobia is actually a superphylum that encompasses 7 subordinate phyla.
The phylotypic stage is the most conserved stage of embryogenesis between species within a phylum. It is the point in which developing embryos of species in the same phylum display maximal similarity. Recently, molecular tools have been used to identify the phylotypic period based on the developmental stage that displays maximal conservation of gene expression or minimal gene sequence divergence between species within a phylum.
division or phylum ("divisio", "phylum")
Coprothermobacter is a genus of rod-shaped microorganisms, belonging to the new bacterial family "Coprothermobacteraceae" of the new phylum "Coprothermobacterota". This taxonomic genus has been reclassified in 2018, after different phylogenetic studies showed that these bacteria represented a deeply branched taxon of the domain "Bacteria" ; consequently, the clade including this genus has been classified in a separate phylum from "Firmicutes", the phylum where it was included before reclassification.
The group, as a part of the phylum Porifera, has been named "Silicispongia" Schmidt, 1862 and "Silicea" Bowerbank, 1864. "Silicarea" is a proposed new phylum based on molecular studies of the phylum Porifera. It consists of the Poriferan classes Demospongiae and Hexactinellida. Some scientists believe that Porifera is polyphyletic/paraphyletic, and that some sponges, the Calcarea, are a separate phylum which was the first to diverge from the main line of kingdom Animalia. Silicarea is considered the next phylum to diverge from the primary animal lineage. 
This section lists the orders of Bacteria within the phylum Spirochaetes.This section lists the orders of Bacteria within the phylum Synergistetes.This section lists the orders of Bacteria within the phylum Thermodesulfobacteria.This section lists the orders of Bacteria within the phylum Thermotogae.This section lists the orders of Bacteria within the phylum Verrucomicrobia.
An early edition of "Bergey’s Manual of Systematic Bacteriology" placed class Mollicutes within phylum Firmicutes, whereas in the announced 2nd edition, they are moved to a separate phylum Tenericutes. The change is motivated by "their unique phenotypic properties, in particular the lack of rigid cell walls, and the general low support by alternative markers". In the "Taxonomic Outline of Bacteria and Archaea" (TOBA Release 7.7), March 2007, the Mollicutes are a class in the phylum Firmicutes.
Armatimonadetes was originally described solely on the basis of environmental 16S rRNA gene clone sequences, and was temporarily titled candidate phylum OP10. However, in 2011 a bacterial strain belonging to the phylum was isolated from an aquatic plant in Japan. The species was named "Armatimonas rosea" and was the first member of its phylum, genus, and species.
If the Ecdysozoa hypothesis is correct, then segmentation of arthropods and annelids either has evolved convergently or has been inherited from a much older ancestor and subsequently lost in several other lineages, such as the non-arthropod members of the Ecdysozoa.
Arthropods belong to phylum Euarthropoda. The phylum is sometimes called Arthropoda, but strictly this term denotes a (putative - see Tactopoda) clade that also encompasses the phylum Onychophora.
A definition of a phylum based on body plan has been proposed by paleontologists Graham Budd and Sören Jensen (as Haeckel had done a century earlier). The definition was posited because extinct organisms are hardest to classify: they can be offshoots that diverged from a phylum's line before the characters that define the modern phylum were all acquired. By Budd and Jensen's definition, a phylum is defined by a set of characters shared by all its living representatives.
Crenarchaeota, second most common archaeal phylum Euryarchaeota, most common archaeal phylum Korarchaeota Nanoarchaeota, ultra-small symbiotes, single known species Thaumarchaeota
This article lists the genera of the bacteria.This phylum used to be known as green non-sulfur bacteriaThermomicrobia phylum is a phenotype of the green non-sulfur bacteria. It is, as its name suggests, thermophilic. Some scientists suggest that the thermomicrobia phylum is not a true bacteriological phylum, but a sub-division of the green non-sulfur division along with the current chloroflexi phylum.