Which is the smallest cell in the world – quora sgas belfast

Mycoplasma gallisepticum (MG) is a bacterium belonging to the class Mollicutes and the family Mycoplasmataceae. It is the causative agent of chronic respiratory disease (CRD) in chickens and infectious sinusitis in turkeys, chickens, game birds, pigeons, and passerine birds of all ages.

Mycoplasmosis is the infection of Mycoplasma bacteria. Mycoplasmas have many defining characteristics. Mycoplasma lack cell walls, have highly variable surface proteins and a distinctive plasma membrane, and are the smallest self-replicating prokaryotes. Mycoplasma can cause disease in humans, animals, insects, and plants. Mycoplasma attach to host epithelial cells, such as in the respiratory tract, which causes cell damage and inflammatory response. There are currently over 100 species of Mycoplasma known. The following have been isolated from wild birds: Mycoplasma buteonis, Mycoplasma corogypsi, Mycoplasma falconis, Mycoplasma gypis, Mycoplasma sturni, and Mycoplasma gallisepticum. M. gallisepticum has the most significant effect on wild birds

Mycoplasma genitalium — It was regarded as a cellular unit with the smallest genome size (size 0.58 Mbp, with 475 genes) until 2003 when a new species of Archaea, namely Nanoarchaeum equitans, was sequenced (0.49 Mbp, with 540 genes). Mycoplasma genitalium

The genome of P. ubique strain HTCC1062 was completely sequenced in 2005 showing that P. ubique has the smallest genome (1,308,759 bp) of any free living organism encoding only 1,354 open reading frames (1,389 genes total). The only species with smaller genomes are intracellular symbionts and parasites, such as Mycoplasma genitalium or Nanoarchaeum equitans.

2. An autonomous self-replicating unit that may exist as functional independent unit of life (as in the case of unicellular organism), or as sub-unit in a multicellular organism (such as in plants and animals) that is specialized into carrying out particular functions towards the cause of the organism as a whole.

There are two distinct types of cells: prokaryotic cells (e.g. bacterial cells) and eukaryotic cells (e.g. plant or animal cell). The main difference between the two is a well-defined nucleus surrounded by a membranous nuclear envelope present only in eukaryotic cells. Despite this difference they share a number of common features: the genetic information is stored in genes, proteins serve as their main structural material, ribosomes are used to synthesize proteins, adenosine triphosphate is the main source of metabolic energy to sustain various cellular processes, and a cell membrane that controls the flow of substances into and out of the cell.

Mycoplasma is a genus of bacteria that lack a cell wall around their cell membrane. Mycoplasma sp. are the smallest self-replicating organisms (~500-1000 genes). For this reason they are suitable models for systems biology and are thought to fit the minimal genome paradigm. They are parasites depending on their hosts, and their metabolism is scarce, reflecting the strong genomic simplification they have suffered from a bacillus-like ancestor. Nevertheless, they can be maintained in vitro. They can be parasitic or saprotrophic .

Mycoplasma genitalium, a parasitic bacterium which lives in the primate bladder, waste disposal organs, genital, and respiratory tracts, is thought to be the smallest known organism capable of independent growth and reproduction. With a size of approximately 200 to 300 nm, M. genitalium is an ultramicrobacterium smaller than other small bacteria, including rickettsia and chlamydia. Smallest organisms

Sphingomonas wittichii RW1 was isolated nearly 20 years ago from the River Elbe , Germany for its ability to completely mineralize the organic backbone of toxic dioxin pollutants (the dibenzo- p -dioxin structure), and to co-oxidize a large number of chlorinated congeners of both dibenzo- p -dioxin and dibenzofuran.

Nanoarchaeum equitans is a species of tiny microbe 400 nm in diameter. It was discovered in 2002 in a hydrothermal vent off the coast of Iceland by Karl Stetter. A thermophile that grows in near-boiling temperatures, Nanoarchaeum appears to be an obligatory symbiont on the archaeon Ignicoccus; it must be in contact with the host organism to survive.

Nanoarchaeum equitans (the riding dwarf), grows exclusively on the surface of Ignicoccus hospitalis (the friendly fire sphere). It thrives in his biotope at temperatures up to 100 °C and could be cultivated for the first time in lab. It is the smallest microorganism known to date, tiny spheres with a diameter of only 400 nm (= 0.0004 mm). By this they exhibit a cell volume of less than 1 % of an E. coli cell which is already in the range of large viruses, like the pox virus. Microbiology, Dr. H. Huber

Image source: Nanoarchaeum equitans and Ignicoccus hospitalis: New Insights into a Unique, Intimate Association of Two Archaea Transmission electron micrographs of ultrathin sections of I . hospitalis and N . equitans following cryoprocessing as described in Materials and Methods. [ I.ho., I. hospitalis cell; CM, cytoplasmic membrane; OM, outer membrane; Pp, periplasm; PV, periplasmic vesicles; N.eq., N. equitans cell. White arrows point to the contact site where the I . hospitalis outer membrane is in close contact with the cytoplasmic membrane. Black arrows, fibrous material in the gap between the two cells. Bars, 1 μm.]

It is rod or crescent shaped and one of the smallest self-replicating cells known, with a length of 0.37-0.89 µm and a diameter of only 0.12-0.20 µm. 30% of the cell’s volume is taken up by its genome. It is gram negative. It recycles dissolved organic carbon. It undergoes regular seasonal cycles in abundance – in summer reaching ~50% of the cells in the temperate ocean surface waters. Thus it plays a major role in the Earth’s carbon cycle. P. ubique and its relatives may be the most abundant organisms in the ocean, and quite possibly the most abundant bacteria in the entire world. It can make up about 25% of all microbial plankton cells, and in the summer they may account for approximately half the cells present in temperate ocean surface water. http://sciencepole.com/pelagibac…