Melainabacteria is a phylum related to

Cyanobacteria Cyanobacteria (), also known as Cyanophyta, are a phylum of gram-negative bacteria that obtain energy via photosynthesis. The name ''cyanobacteria'' refers to their color (), which similarly forms the basis of cyanobacteria's common name, bl ...

. Organisms belonging to this phylum have been found in the human gut and various aquatic habitats such as groundwater. By analyzing genomes of Melainabacteria, predictions are possible about the cell structure and metabolic abilities. The bacterial cell is similar to cyanobacteria in being surrounded by two membranes. It differs from cyanobacteria in its ability to move by

flagella A flagellum (; ) is a hairlike appendage that protrudes from certain plant and animal sperm cells, and from a wide range of microorganisms to provide motility. Many protists with flagella are termed as flagellates. A microorganism may have fro ...

(like gram-negative flagella), though some members (e.g. Gastranaerophilales) lack flagella. Melainabacteria are not able to perform

photosynthesis Photosynthesis is a process used by plants and other organisms to convert light energy into chemical energy that, through cellular respiration, can later be released to fuel the organism's activities. Some of this chemical energy is stored in ...

, but obtain energy by

fermentation Fermentation is a metabolic process that produces chemical changes in organic substrates through the action of enzymes. In biochemistry, it is narrowly defined as the extraction of energy from carbohydrates in the absence of oxygen. In food p ...

Phylogeny

Classification

* Class "Melainabacteria" Soo et al. 2014 Vampirovibrionia"(ACD20) ** Order " Caenarcanales" corrig. Soo et al. 2014 Caenarcaniphilales"_Soo_et_al._2014.html" ;"title="Caenarcaniphilales.html" ;"title="Caenarcaniphilales">Caenarcaniphilales" Soo et al. 2014">Caenarcaniphilales.html" ;"title="Caenarcaniphilales">Caenarcaniphilales" Soo et al. 2014*** Family "Caenarcanaceae" **** Genus "''Ca.'' Caenarcanum" Soo et al. 2014 ***** "''Ca.'' Caenarcanum bioreactoricola, C. bioreactoricola" Soo et al. 2014 ** Order " Obscuribacterales" Soo et al. 2014 *** Family " Obscuribacteraceae" **** Genus "''Ca.'' Obscuribacter" Soo et al. 2014 ***** "''Ca.'' O. phosphatis" Soo et al. 2014 ** Order " Vampirovibrionales" Soo et al. 2015 *** Family " Vampirovibrionaceae" Soo 2015 **** Genus '' Vampirovibrio'' Gromov & Mamkayeva 1972 ex Gromov & Mamkaeva 1980 ***** '' V. chlorellavorus'' Gromov & Mamkayeva 1972 ex Gromov & Mamkaeva 1980 ** Order " Gastranaerophilales" Soo et al. 2014 *** Family CAJFVJ01 **** 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" **** 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.'' 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 **** Genus "''Ca.'' Scatousia" Gilroy et al. 2021 ***** "''Ca.'' S. excrementigallinarum" Gilroy et al. 2021 ***** "''Ca.'' S. excrementipullorum" Gilroy et al. 2021

Ecological Niche

Melainabacteria 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 is often found in natural environments such as groundwater aquifers and lake sediment, as well as soil and bioreactors. Melainabacteria are also found in the aphotic zone 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 and Cyanobacteria are related, 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), also called the Great Oxygenation Event, the Oxygen Catastrophe, the Oxygen Revolution, the Oxygen Crisis, or the Oxygen Holocaust, was a time interval during the Paleoproterozoic era when the Earth's atmospher ...

(GOE) that occurred 2.4 billion years ago altered the course of life on Earth forever by increasing the abundance of oxygen in the atmosphere. Bacteria that existed before the GEO did not rely on the presence of oxygen as a source for metabolism, such as the billion-year-old Cyanobacteria. Melainabacteria is a close relative to Cyanobacteria, though Melainabacteria diverged and 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 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 a protein that catalyzes the formation of the energy storage molecule adenosine triphosphate (ATP) using adenosine diphosphate (ADP) and inorganic phosphate (Pi). It is classified under ligases as it changes ADP by the formation ...

. They are able to use Fe hydrogenases for production that can be consumed by other microorganisms. Melainabacteria from the human gut also 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 have been found to potentially play a role in digesting fiber in the human gut, and are more commonly 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 are unsure of ''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," funded by various organizations such as the

National Institutes of Health The National Institutes of Health, commonly referred to as NIH (with each letter pronounced individually), is the primary agency of the United States government responsible for biomedical and public health research. It was founded in the lat ...

, 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 death ...

, The Hartwell Foundation, the

Arnold and Mabel Beckman Foundation Arnold Orville Beckman (April 10, 1900 – May 18, 2004) was an American chemist, inventor, investor, and philanthropist. While a professor at California Institute of Technology, he founded Beckman Instruments based on his 1934 invention of th ...

, the U.S. Department of Energy, the

European Molecular Biology Organization The European Molecular Biology Organization (EMBO) is a professional, non-profit organization of more than 1,800 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, in the United Kingdom. It was established in 1936 with legacies from the pharmaceutical magnate Henry Wellcome (founder of one of the predecessors of Glaxo ...

References

External links

What Are Cyanobacteria And What Are Its Types?

Webserver for Cyanobacteria Research

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