The glaucophytes, also known as glaucocystophytes or glaucocystids, are a small group of freshwater microscopic algae Algae are a large and diverse group of simple, typically autotrophic organisms, ranging from unicellular to multicellular forms, such as the giant kelps that grow to 65 meters in length. The US Algal Collection is represented by almost 300,000 accessioned and inventoried herbarium specimens. The largest and most complex marine forms are called.[1] Together with the red algae The Red algae (or Rhodophyta, pronounced /roʊˈdɒfɨtə, ˌroʊdəˈfaɪtə/, from Greek: ῥόδον = rose + φυτόν (phyton) = plant, thus red plant) are one of the oldest groups of eukaryotic algae, and also one of the largest, with about 5,000–6,000 species of mostly multicellular, marine algae, including many notable seaweeds. Other (Rhodophyta) and green algae plus land plants (Viridiplantae Viridiplantae are a clade comprising the green algae and land plants or Chloroplastida), they form the Archaeplastida The Archaeplastida are a major group of eukaryotes, comprising the red and green algae and the land plants, together with a small group called the glaucophytes. The plastids of all of these organisms are surrounded by two membranes, suggesting they developed directly from endosymbiotic cyanobacteria. In all other groups, plastids are surrounded by. However, the relationships between the red algae, green algae and glaucophytes are unclear,[2] in large part due to limited study of the glaucophytes.
The glaucophytes are of interest to biologists studying the development of chloroplasts, because some studies suggest that they may be similar to the original alga type that led to green plants and red algae.[1][3]
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Characteristics
The chloroplasts Chloroplasts are organelles found in plant cells and other eukaryotic organisms that conduct photosynthesis. Chloroplasts capture light energy to conserve free energy in the form of ATP and reduce NADP to NADPH through a complex set of processes called photosynthesis of glaucophytes are known as cyanelles. Unlike plastids in other organisms they have a peptidoglycan Peptidoglycan, also known as murein, is a polymer consisting of sugars and amino acids that forms a mesh-like layer outside the plasma membrane of bacteria , forming the cell wall. The sugar component consists of alternating residues of β-(1,4) linked N-acetylglucosamine and N-acetylmuramic acid. Attached to the N-acetylmuramic acid is a peptide layer that is believed to be a relic of the endosymbiotic The endosymbiotic theory concerns the origins of mitochondria and plastids , which are organelles of eukaryotic cells. According to this theory, these organelles originated as separate prokaryotic organisms that were taken inside the cell as endosymbionts. Mitochondria developed from proteobacteria (in particular, Rickettsiales or close relatives) origin of plastids from cyanobacteria Cyanobacteria is a phylum of bacteria that obtain their energy through photosynthesis. The name "cyanobacteria" comes from the color of the bacteria (Greek: κυανός (kyanós) = blue).[1] Glaucophytes contain the photosynthetic pigment chlorophyll a Chlorophyll a is a form of chlorophyll. Chlorophyll a is mainly used in light reactions used in photosynthesis. It loses excited electrons allowing them to move to the electron acceptor which in turn moves it through the electron transport chain. It absorbs energy from the violet-blue and orange-red wavelengths. It has relatively high Kreft's.[1] Along with red algae[1] and cyanobacteria they harvest light via phycobilisomes Phycobilisomes are light harvesting antennae of photosystem II in cyanobacteria, red algae and glaucophytes, structures consisting largely of phycobiliproteins Phycobiliproteins are water-soluble proteins present in cyanobacteria and certain algae that capture light energy, which is then passed on to chlorophylls during photosynthesis. Phycobiliproteins are formed of a complex between proteins and covalently bound phycobilins that act as chromophores (the light-capturing part). They are most important. The green algae and land plants have lost that pigment.[not in citation given]
Glaucophytes have mitochondria In cell biology, a mitochondrion is a membrane-enclosed organelle found in most eukaryotic cells. These organelles range from 0.5 to 10 micrometers (μm) in diameter. Mitochondria are sometimes described as "cellular power plants" because they generate most of the cell's supply of adenosine triphosphate (ATP), used as a source of with flat cristae, and undergo open mitosis Mitosis is the process by which a eukaryotic cell separates the chromosomes in its cell nucleus into two identical sets in two nuclei. It is generally followed immediately by cytokinesis, which divides the nuclei, cytoplasm, organelles and cell membrane into two cells containing roughly equal shares of these cellular components. Mitosis and without centrioles A centriole is a barrel-shaped cell structure found in most animal eukaryotic cells, though absent in higher plants and most fungi. The walls of each centriole are usually composed of nine triplets of microtubules . Deviations from this structure include Drosophila melanogaster embryos, with nine doublets, and Caenorhabditis elegans sperm cells. Motile forms have two unequal flagella A flagellum is a tail-like projection that protrudes from the cell body of certain prokaryotic and eukaryotic cells, and functions in locomotion. There are some notable differences between prokaryotic and eukaryotic flagella, such as protein composition, structure, and mechanism of propulsion. An example of a flagellated bacterium is the ulcer-, which may have fine hairs and are anchored by a multilayered system of microtubules Microtubules are one of the components of the cytoskeleton. They have a diameter of 25 nm and length varying from 200 nanometers to 25 micrometers. Microtubules serve as structural components within cells and are involved in many cellular processes including mitosis, cytokinesis, and vesicular transport, both of which are similar to forms found in some green algae.
Genera
There are only 13 species of glaucophytes known, none of which is particularly common in nature.[1] The three included genera In biology, a genus is a low-level taxonomic rank (a taxon) used in the classification of living and fossil organisms, which is an example of definition by genus and differentia. The term comes from Latin genus "descent, family, type, gender", cognate with Greek: γένος – genos, "race, stock, kin" are:
- Glaucocystis is non-motile, though it retains very short vestigial Vestigiality describes homologous characters of organisms that have seemingly lost all or most of their original function in a species through evolution. These may take various forms such as anatomical structures, behaviors and biochemical pathways. Some of these disappear early in embryonic development, but others are retained in adulthood flagella, and has a cellulose Cellulose is an organic compound with the formula n, a polysaccharide consisting of a linear chain of several hundred to over ten thousand β(1→4) linked D-glucose units wall.
- Cyanophora is motile and lacks a cell wall.
- Gloeochaete has both motile and non-motile stages, and has a cell wall that does not appear to be composed of cellulose.
References
- ^ a b c d e f Patrick J. Keeling (2004). "Diversity and evolutionary history of plastids and their hosts". American Journal of Botany 91: 1481–1493. doi A digital object identifier is a character string used to uniquely identify an electronic document or other object. Metadata about the object is stored in association with the DOI name and this metadata may include a location, such as a URL, where the object can be found. The DOI for a document is permanent, whereas its location and other metadata:10.3732/ajb.91.10.1481. http://www.amjbot.org/cgi/content/full/91/10/1481.
- ^ Jeffrey D. Palmer, Douglas E. Soltis & Mark W. Chase (2004). "The plant tree of life: an overview and some points of view". American Journal of Botany 91: 1437–1445. doi A digital object identifier is a character string used to uniquely identify an electronic document or other object. Metadata about the object is stored in association with the DOI name and this metadata may include a location, such as a URL, where the object can be found. The DOI for a document is permanent, whereas its location and other metadata:10.3732/ajb.91.10.1437. http://www.amjbot.org/cgi/content/full/91/10/1437.
- ^ Eunsoo Kim & Linda E. Graham (2008). "EEF2 analysis challenges the monophyly of Archaeplastida and Chromalveolata" (Free full text). PLoS ONE PLoS ONE is an open access, "online only", scientific journal from the Public Library of Science. It covers primary research from any discipline within science and medicine. All submissions go through a rigorous, internal and external pre-publication peer review but are not excluded on the basis of lack of perceived importance or 3 (7): e2621. doi A digital object identifier is a character string used to uniquely identify an electronic document or other object. Metadata about the object is stored in association with the DOI name and this metadata may include a location, such as a URL, where the object can be found. The DOI for a document is permanent, whereas its location and other metadata:10.1371/journal.pone.0002621. PMID A PMID is a unique number assigned to each PubMed citation of life sciences and biomedical scientific journal articles. The related Pubmed Central archive may additionally assign a separate number, a PMCID (PubMed Central Identifier), normally written with a PMC prefix 18612431. PMC PubMed Central is a free digital database of full-text scientific literature in biomedical and life sciences. It grew from the online Entrez PubMed biomedical literature search system. PubMed Central was developed by the U.S. National Library of Medicine as an online archive of biomedical journal articles 2440802. http://www.plosone.org/article/info:doi/10.1371/journal.pone.0002621.
