Prasinococcus

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Prasinococcus
Scientific classification OOjs UI icon edit-ltr.svg
(unranked): Viridiplantae
Phylum: Prasinodermophyta
Class: Palmophyllophyceae
Order: Prasinococcales
Family: Prasinococcaceae
Genus: Prasinococcus
Miyashita & Chihara 1993 [1]
Species:
P. capsulatus
Binomial name
Prasinococcus capsulatus
Miyashita & Chihara 1993 [1]

Prasinococcus is a monotypic genus of green algae, containing the only species Prasinococcus capsulatus, in the monotypic family Prasinococcaceae. [2] This unicellular algal species was discovered in 1990 in the West Pacific Ocean and has characteristic reproduction methods as well as an interesting and potentially exploitable morphology. This is the only species in the genus, though various strains exist, for example URI 266G is the Atlantic clone. [3]

Contents

Discovery

Prasinococcus capsulatus, the only currently known member of this genus, was discovered in the West Pacific Ocean during a cruise by the research vessel Sohgen-maru in November–December 1990. The name "'capsulatus'" coming from the alga's large capsule which surrounds the cell. [1]

Morphology

Prasinococcus have a firm cell wall lacking scales and also lack flagella. The mitochondrial lobe and chloroplast outer membrane both protrude into the pyrenoid matrix which is considered characteristic of the genus. The cell wall has a protruding circular collar which is surrounded by holes which penetrate the cell wall. Its method of asexual reproduction is also considered characteristic - after cell division one daughter cell remains within the original cell wall while the other is extruded. [1]

The most notable feature of P. capsulatus morphology is its large capsule composed of an exo-polysaccharide which has been dubbed "capsulan". Capsulan is thought to be synthesised in the Golgi and then secreted through the decapore (a specialised circle of 10 pores through the cell wall). After exiting the decapore capsulan becomes visible and it is thought that it cross links with divalent ions in the seawater. Research is currently underway to find potential applications for capsulan and how to maximise its production. [3]

The capsule's function is not clearly defined but various explanations have been suggested. One is that it offers protection to newly divided cells which lack a thick cell wall, another is that it provides a template for daughter cells to synthesise their new cell wall. The capsule may also interfere with filter feeding, thus reducing predation. In similar species, capsules have been noted for their antibacterial properties [4] and a conspicuous lack of bacteria as well as viral particles in impure samples of P. capsulatus has been observed. [3]

The pigments of Prasinococcus include chlorophylls a and b, prasinoxanthin, Mg 2, 4-diviriylphaeoporphyrin a5 monomethyl ester (Mg 2, 4-D) and 5, 6-epoxy-3, 3′-dihydroxy-5, 6, 7′, 8′-tetrahydro-β-ε-caroten-11′ and 19-olide (uriolide). [1]

Reproduction

Sexual reproduction has not been observed in P. capsulatus but its mode of asexual reproduction is quite distinctive. The cell splits into two daughter cells while remaining inside the original cell wall, one daughter cell then begins to enlarge, while the other is pushed out of a small hole in the parental cell wall. The larger cell remains in the original cell wall while the other migrates to the edge of the capsule which surrounds them both. Before leaving the parental capsule this daughter has synthesised its own firm cell wall after which it leaves the parental capsule and begins to produce its own capsule. [1]

Others claim that this mode of reproduction immature cells with thinner walls older cells with thicker walls must first discard the paternal cell wall before undergoing binary fission and then each daughter cell produces its own new cell wall. This is evidenced by abandoned cell walls residing in mature cells' capsules. [3]

Distribution

P. capsulatus is an important contributor to oceanic biomass especially in late winter to early spring. Its range covers much of the West Pacific and West Atlantic Oceans. [3]

Bio-remediation

P. capsulatus is currently being studied for use in Carbon Dioxide capture, especially important as it recycles this carbon into capsulan which may be a useful compound. [5]

Related Research Articles

<span class="mw-page-title-main">Chlorophyceae</span> Class of green algae

The Chlorophyceae are one of the classes of green algae, distinguished mainly on the basis of ultrastructural morphology. They are usually green due to the dominance of pigments chlorophyll a and chlorophyll b. The chloroplast may be discoid, plate-like, reticulate, cup-shaped, spiral- or ribbon-shaped in different species. Most of the members have one or more storage bodies called pyrenoids located in the chloroplast. Pyrenoids contain protein besides starch. Some green algae may store food in the form of oil droplets. They usually have a cell wall made up of an inner layer of cellulose and outer layer of pectose.

<i>Chlamydomonas</i> Genus of algae

Chlamydomonas is a genus of green algae consisting of about 150 species of unicellular flagellates, found in stagnant water and on damp soil, in freshwater, seawater, and even in snow as "snow algae". Chlamydomonas is used as a model organism for molecular biology, especially studies of flagellar motility and chloroplast dynamics, biogenesis, and genetics. One of the many striking features of Chlamydomonas is that it contains ion channels (channelrhodopsins) that are directly activated by light. Some regulatory systems of Chlamydomonas are more complex than their homologs in Gymnosperms, with evolutionarily related regulatory proteins being larger and containing additional domains.

<i>Halimeda</i> Genus of algae

Halimeda is a genus of green macroalgae. The algal body (thallus) is composed of calcified green segments. Calcium carbonate is deposited in its tissues, making it inedible to most herbivores. However one species, Halimeda tuna, was described as pleasant to eat with oil, vinegar, and salt.

<i>Trachelomonas</i> Genus of euglenoids

Trachelomonas is a genus of swimming, free-living euglenoids characterized by the presence of a shell-like covering called a lorica. Details of lorica structure determine the classification of distinct species in the genus. The lorica can exist in spherical, elliptical, cylindrical, and pyriform (pear-shaped) forms. The lorica surface can be smooth, punctuate or striate and range from hyaline, to yellow, or brown. These colors are due to the accumulation of ferric hydroxide and manganic oxide deposited with the mucilage and minerals that comprise the lorica. In Trachelomonas, the presence of a lorica obscures cytoplasmic details of the underlying cell. In each Trachelomonas cell, there is a gap at the apex of the lorica from which the flagellum protrudes. Thickening around this gap results in a rim-like or collar-like appearance. During asexual reproduction, the nucleus divides yielding two daughter cells one of which exits through the opening in the lorica. This new cell then synthesizes its own new lorica.

<i>Coelastrum</i> Genus of algae

Coelastrum is a genus of green algae in the Scenedesmaceae family. It is a common component of the phytoplankton in freshwater habitats such as ponds, lakes, waterfalls, and temporary pools of water, particularly eutrophic ones. The genus has a more or less cosmopolitan distribution, although some species appear to have more restricted geographical distributions.

Pycnococcaceae is a family of green algae in the order Pseudoscourfieldiales. The defining features of this family include the single invagination of the pyrenoid where the mitochondrial membrane fits into it and the "decapore" - a ring of 10 pores through the thick cell wall.

Coelastropsis is a genus of green algae in the family Scenedesmaceae, containing the single species Coelastropsis costata. It is found in freshwater lakes and bogs, usually associated with mosses and filamentous algae. It has been recorded in Europe, Cuba and possibly New Zealand.

<i>Pediastrum</i> Genus of algae

Pediastrum is a genus of green algae, in the family Hydrodictyaceae. It is a photoautotrophic, nonmotile coenobial green alga that inhabits freshwater environments.

<i>Platydorina</i> Genus of algae

Platydorina is a genus of microscopic green algae in the family Volvocaceae. It contains only one species, Platydorina caudata. It was described by Charles Atwood Kofoid in 1899.

<i>Prasinoderma</i> Genus of algae

Prasinoderma is a genus of green algae in the phylum Prasinodermophyta. Both species in the genus are unicellular, but P. coloniale forms loose sticky colonies.

<i>Sorastrum</i> Genus of algae

Sorastrum is a genus of green algae in the family Hydrodictyaceae. It is a component of the phytoplankton of freshwater ponds, lakes, and ditches. Sorastrum is common in tropical to temperate regions of the world, but due to its small size it is often overlooked.

<i>Stephanosphaera</i> Genus of algae

Stephanosphaera is a genus of green algae in the family Haematococcaceae, containing the single species Stephanosphaera pluvialis. It forms colonies of flagellated cells. Although it was once placed in the family Volvocaceae, it is not closely related to them; its sister is the unicellular genus Balticola.

<i>Tetraedron</i> Genus of algae

Tetraedron is a genus of green algae in the family Hydrodictyaceae. It may also be spelled as Tetraëdron.

Gilbertsmithia is a genus of green algae in the family Scenedesmaceae, containing the single species Gilbertsmithia grandis. It was named after the American botanist Gilbert Morgan Smith. This remarkable alga has only been recorded once from a muddy rainwater pool in Madras, India.

Deuterocharacium is a genus of green algae in the family Characiaceae. It is found in freshwater habitats, attached to algae or detritus. It is rare and has only been recorded from Europe.

<i>Pyrocystis fusiformis</i> Species of single-celled organism

Pyrocystis fusiformis is a non-motile, tropical, epipelagic, marine dinoflagellate, reaching lengths of up to 1 millimetre (0.039 in). P. fusiformis display bioluminescence when disturbed or agitated. In coastal marine waters, this dinoflagellate causes glowing effects after dark. P. fusiformis was first described in the Proceedings of the Royal Society of London in 1876.

Pinguiochrysidaceae is a family of marine Heterokontophyta. It is the only family in the order Pinguiochrysidales, which is the only order in the class Pinguiophyceae. It includes five species of unicellular organisms with high concentration of polyunsaturated fatty acids in the cytoplasm. The other common features are the lack of cell wall and the tendency for flagella loss even on the stage of zoospore, which is unusual for heterokonts. One species inhabits benthic substates and is able to produce lorica with one or more tubular necks. The other species live in the plankton.

<i>Acaryochloris marina</i> Species of bacterium

Acaryochloris marina is a symbiotic species of the phylum Cyanobacteria that produces chlorophyll d, allowing it to use far-red light, at 770 nm wavelength.

Capsulan is the exopolysaccharide which makes up the thick capsule surrounding the unicellular alga Prasinococcus capsulatus.

Bracteamorpha is a genus of green algae in the order Sphaeropleales, and is the only genus in the family Bracteamorphaceae. It contains a single species, Bracteamorpha trainorii.

References

  1. 1 2 3 4 5 6 Miyashita, Hideaki; Ikemoto, Hisato; Kurano, Norihide; Miyachi, Sigetoh; Chihara, Mitsuo (1993). "Prasinococcus capsulatus gen. Et sp. Nov., a new marine coccoid prasinophyte". The Journal of General and Applied Microbiology. 39 (6): 571–582. doi: 10.2323/jgam.39.571 .
  2. ↑ Guiry, M.D.; Guiry, G.M. "Prasinococcaceae". AlgaeBase . World-wide electronic publication, National University of Ireland, Galway.
  3. 1 2 3 4 5 Sieburth, John McN.; Keller, Maureen D.; Johnson, Paul W.; Myklestad, Sverre M. (October 1999). "WIDESPREAD OCCURRENCE OF THE OCEANIC ULTRAPLANKTER, PRASINOCOCCUS CAPSULATUS (PRASINOPHYCEAE), THE DIAGNOSTIC "GOLGI-DECAPORE COMPLEX" AND THE NEWLY DESCRIBED POLYSACCHARIDE "CAPSULAN"". Journal of Phycology. 35 (5): 1032–1043. doi:10.1046/j.1529-8817.1999.3551032.x. S2CID   86059264.
  4. ↑ Davidson AT, Marchant HJ (1987). "Binding of manganese by Antarctic Phaeocystis pouchetii and the role of bacteria in its release". Marine Biology. 95 (3): 481–487. doi:10.1007/BF00409577. S2CID   84709702.
  5. ↑ Kurano N, Ikemoto H, Miyashita H, Hasegawa T, Hata H, Miyachi S (1995). "Fixation and utilization of carbon dioxide by microalgal photosynthesis". Energy Conversion and Management. 36 (6–9): 689–692. doi:10.1016/0196-8904(95)00099-Y.
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