"'' Candidatus'' Melainobacteriota" is a

monotypic In biology, a monotypic taxon is a taxonomic group (taxon) that contains only one immediately subordinate taxon. A monotypic species is one that does not include subspecies or smaller, infraspecific taxa. In the case of genera, the term "unisp ...

phylum In biology, a phylum (; : phyla) is a level of classification, or taxonomic rank, that is below Kingdom (biology), kingdom and above Class (biology), class. Traditionally, in botany the term division (taxonomy), division has been used instead ...

bacteria Bacteria (; : bacterium) are ubiquitous, mostly free-living organisms often consisting of one Cell (biology), biological cell. They constitute a large domain (biology), domain of Prokaryote, prokaryotic microorganisms. Typically a few micr ...

that is the

sister A sister is a woman or a girl who shares parents or a parent with another individual; a female sibling. The male counterpart is a brother. Although the term typically refers to a familial relationship, it is sometimes used endearingly to ref ...

phylum of the phylum

Cyanobacteria Cyanobacteria ( ) are a group of autotrophic gram-negative bacteria that can obtain biological energy via oxygenic photosynthesis. The name "cyanobacteria" () refers to their bluish green (cyan) color, which forms the basis of cyanobacteri ...

(named under the '' Botanical Code''). It has one

class Class, Classes, or The Class may refer to: Common uses not otherwise categorized * Class (biology), a taxonomic rank * Class (knowledge representation), a collection of individuals or objects * Class (philosophy), an analytical concept used d ...

Vampirovibrionophyceae. '' Vampirovibrio chlorellavorus'' is the only species of the phylum that has been grown in

cell culture Cell culture or tissue culture is the process by which cell (biology), cells are grown under controlled conditions, generally outside of their natural environment. After cells of interest have been Cell isolation, isolated from living tissue, ...

. '' Candidatus''

species A species () is often defined as the largest group of organisms in which any two individuals of the appropriate sexes or mating types can produce fertile offspring, typically by sexual reproduction. It is the basic unit of Taxonomy (biology), ...

of melainabacteria have been discovered through

DNA Deoxyribonucleic acid (; DNA) is a polymer composed of two polynucleotide chains that coil around each other to form a double helix. The polymer carries genetic instructions for the development, functioning, growth and reproduction of al ...

and

RNA Ribonucleic acid (RNA) is a polymeric molecule that is essential for most biological functions, either by performing the function itself (non-coding RNA) or by forming a template for the production of proteins (messenger RNA). RNA and deoxyrib ...

sequence analysis In bioinformatics, sequence analysis is the process of subjecting a DNA, RNA or peptide sequence to any of a wide range of analytical methods to understand its features, function, structure, or evolution. It can be performed on the entire genome ...

of samples from soil, the human gut, and various aquatic habitats such as groundwater. By analyzing genomes of melainabacteria, predictions are possible about their cell structure and metabolic abilities. The deduced structure of the bacterial cell is similar to cyanobacteria in being surrounded by two membranes. It differs from cyanobacteria in its predicted ability to move by

flagella A flagellum (; : flagella) (Latin for 'whip' or 'scourge') is a hair-like appendage that protrudes from certain plant and animal sperm cells, from fungal spores ( zoospores), and from a wide range of microorganisms to provide motility. Many pr ...

(like gram-negative flagella), though some members (e.g. Gastranaerophilales) appear to lack flagella. It is predicted that melainabacteria are not able to perform

photosynthesis Photosynthesis ( ) is a system of biological processes by which photosynthetic organisms, such as most plants, algae, and cyanobacteria, convert light energy, typically from sunlight, into the chemical energy necessary to fuel their metabo ...

, but obtain energy by

fermentation Fermentation is a type of anaerobic metabolism which harnesses the redox potential of the reactants to make adenosine triphosphate (ATP) and organic end products. Organic molecules, such as glucose or other sugars, are catabolized and reduce ...

Treatments

Melainabacteria has been treated as: * The phylum "Melainabacteria" (more properly "''Candidatus'' Melainabacteria") when its DNA was discovered in 2013. * The class "Melainabacteria" under Cyanobacteria in Soo et al. (2014). * The phylum "''Candidatus'' Melainobacteriota", the 2013 name corrected to match new bacteriological rules. * The class "Vampirovibriophyceae" under Cyanobacteria in Strunecký and Mareš 2023, with the corrected spelling Vampirovibrionophyceae. * The class Vampirovibrionia under Cyanobacterota in 2023, which was validated under bacteriological rules in 2024. It was not realized until 2015 that this group actually includes one cultured bacterium. Names proposed prior to this point are written under the assumption that they describe an uncultured group and are ''Candidatus''. Names proposed without ''Candidatus'' after this point use the cultured species in the description. Removal of the ''Candidatus'' prefix does not happen automatically; instead, an author must make a separate valid publication. Treating this group as a phylum would place it at the same

taxonomic rank In biology, taxonomic rank (which some authors prefer to call nomenclatural rank because ranking is part of nomenclature rather than taxonomy proper, according to some definitions of these terms) is the relative or absolute level of a group of or ...

as Cyanobacteria, or in the new bacteriological rule, Cyanobacteriota.

Phylogeny

Classification

* Phylum "''Ca''. Melainobacteriota" corrig. Di Rienzi et al. 2013 ** Class Vampirovibrionophyceae Strunecký and Mareš 2023 (ACD20) *** Order "Caenarcanales" corrig. Soo et al. 2014 Soo et al. 2014">Caenarcaniphilales" Soo et al. 2014**** Family "Caenarcanaceae" Chuvochina et al. 2023 ***** Genus "''Ca.'' Caenarcanum" Soo et al. 2014 ****** "''Ca.'' C. bioreactoricola" Soo et al. 2014 *** Order Vampirovibrionales Chuvochina et al. 2024 **** Family Vampirovibrionaceae Chuvochina et al. 2024 ***** Genus '' Vampirovibrio'' Gromov & Mamkayeva 1972 ex Gromov & Mamkaeva 1980 ****** '' V. chlorellavorus'' Gromov & Mamkayeva 1972 ex Gromov & Mamkaeva 1980 *** Order "''Ca.'' Gastranaerophilales" Soo et al. 2014 **** Family "Adamsellaceae" Pallen, Rodriguez-R & Alikhan 2022 AJFVJ01***** Genus "''Ca.'' Adamsella" Glendinning et al. 2020 ****** "''Ca.'' A. avium" Glendinning et al. 2020 **** Family "RUG14156" ***** Genus "''Ca.'' Galligastranaerophilus" Gilroy et al. 2021 ****** "''Ca.'' G. faecipullorum" Gilroy et al. 2021 ****** "''Ca.'' G. gallistercoris" Gilroy et al. 2021 ****** "''Ca.'' G. intestinavium" Gilroy et al. 2021 ****** "''Ca.'' G. intestinigallinarum" Gilroy et al. 2021 **** Family "Gastranaerophilaceae" Gilroy et al. 2021 ***** Genus "''Ca.'' Avigastranaerophilus" Gilroy et al. 2021 ****** "''Ca.'' A. faecigallinarum" Gilroy et al. 2021 ***** Genus "''Ca.'' Gastranaerophilus" Soo et al. 2014 ****** "''Ca.'' G. phascolarctosicola" Soo et al. 2014 ****** "''Ca.'' G. termiticola" Utami et al. 2018 ***** Genus "''Ca.'' Limenecus" Gilroy et al. 2021 ****** "''Ca.'' L. avicola" Gilroy et al. 2021 ***** Genus "''Ca.'' Scatenecus" Gilroy et al. 2021 ****** "''Ca.'' S. faecavius" Gilroy et al. 2021 ***** Genus "''Ca.'' Scatousia" Gilroy et al. 2021 ****** "''Ca.'' S. excrementigallinarum" Gilroy et al. 2021 ****** "''Ca.'' S. excrementipullorum" Gilroy et al. 2021 ***** Genus "''Ca.'' Spyradomonas" Gilroy et al. 2021 ****** "''Ca.'' S. excrementavium" Gilroy et al. 2021 ***** Genus "''Ca.'' Stercorousia" Gilroy et al. 2021 ****** "''Ca.'' S. faecigallinarum" Gilroy et al. 2021

Ecological niche

Melainabacteria

nucleic acids Nucleic acids are large biomolecules that are crucial in all cells and viruses. They are composed of nucleotides, which are the monomer components: a 5-carbon sugar, a phosphate group and a nitrogenous base. The two main classes of nucleic a ...

can be found in a range of environments, including soil, water, and animal habitats. They can be often be found in the gut of humans and in the respiratory tract, oral environments, and skin surface, though rarely. Melainabacteria nucleic acids are often found in natural environments such as groundwater aquifers and lake sediment, soil, bioreactor, and the

aphotic zone The aphotic zone (aphotic from Greek prefix + "without light") is the portion of a lake or ocean where there is little or no sunlight. It is formally defined as the depths beyond which less than 1 percent of sunlight penetrates. Above the apho ...

of aquatic environments such as lake sediment and aquifers. Cyanobacteria bloom in freshwater systems as a result of excess nutrients and high temperatures, resulting in a scum on the water surface that resembles spilled paint. Because melainabacteria is a type of Cyanobacteria, it has raised concern because melainabacteria thrive in groundwater systems. The genomes of melainabacteria were found to be bigger when found in aquifer systems and algal cultivation ponds than when in the mammalian gut environment.

Origin

The

Great Oxygenation Event The Great Oxidation Event (GOE) or Great Oxygenation Event, also called the Oxygen Catastrophe, Oxygen Revolution, Oxygen Crisis or Oxygen Holocaust, was a time interval during the Earth's Paleoproterozoic era when the Earth's atmosphere and ...

(GOE) increased the abundance of oxygen in the atmosphere. Bacteria that existed before the GEO did not rely on oxygen, such as the billion-year-old cyanobacteria. Melainabacteria do not photosynthesize. Cyanobacteria produced atmospheric oxygen and supported the development of early plant cells.

Genome

The genomes of melainabacteria organisms isolated from ground water indicate that the organism has the capacity to fix nitrogen. Melainabacteria are predicted to lack linked electron transport chains, but have multiple methods to generate a membrane potential which can then produce ATP via

ATP synthase ATP synthase is an enzyme that catalyzes the formation of the energy storage molecule adenosine triphosphate (ATP) using adenosine diphosphate (ADP) and inorganic phosphate (Pi). ATP synthase is a molecular machine. The overall reaction catalyzed ...

. They are thought to be able to use Fe

hydrogenase A hydrogenase is an enzyme that Catalysis, catalyses the reversible Redox, oxidation of molecular hydrogen (H2), as shown below: Hydrogen oxidation () is coupled to the reduction of electron acceptors such as oxygen, nitrate, Ferric, ferric i ...

s for production that can be consumed by other microorganisms. Melainabacteria from the human gut also are thought to synthesize several B and K vitamins, which suggests that these bacteria are beneficial to their host because they are consumed along with plant fibers.

Animal habitats

Melainabacteria may play a role in digesting fiber in the human gut, and their nucleic acids are more commonly found in herbivorous mammals and those with plant-rich diets. Because plant diets require more fiber break-down, melainabacteria may aid in this digestive function. However, scientists do not know ''why'' these microbes are in the gut and how they got there. Ongoing studies such as, "The human gut and groundwater harbor non-photosynthetic bacteria belonging to a new candidate phylum sibling to Cyanobacteria," are funded by various organizations such as the

National Institutes of Health The National Institutes of Health (NIH) is the primary agency of the United States government responsible for biomedical and public health research. It was founded in 1887 and is part of the United States Department of Health and Human Service ...

, the

David and Lucile Packard Foundation The David and Lucile Packard Foundation is a private foundation that provides grants to not-for-profit organizations. It was created in 1964 by David Packard (co-founder of HP) and his wife Lucile Salter Packard. Following David Packard's dea ...

, The Hartwell Foundation, the Arnold and Mabel Beckman Foundation, the

U.S. Department of Energy The United States Department of Energy (DOE) is an executive department of the U.S. federal government that oversees U.S. national energy policy and energy production, the research and development of nuclear power, the military's nuclear we ...

, the

European Molecular Biology Organization The European Molecular Biology Organization (EMBO) is a professional, non-profit organization of more than 2,100 life scientists. Its goal is to promote research in life science and enable international exchange between scientists. It co-funds cour ...

and the

Wellcome Trust The Wellcome Trust is a charitable foundation focused on health research based in London, United Kingdom. It was established in 1936 with legacies from the pharmaceutical magnate Henry Wellcome (founder of Burroughs Wellcome, one of the predec ...

References

External links

What Are Cyanobacteria And What Are Its Types?

Webserver for Cyanobacteria Research

CyanoBase
{{Taxonbar, from=Q20721206, from2=Q124340683 Environmental chemistry Bacteria phyla Taxa described in 2013 Candidatus taxa