Diatom
Diatoms are tiny eukaryotic algae. They are a common type of phytoplankton. Most are single cells, but some form chains or simple colonies.
Diatoms | |
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Marine diatoms | |
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Class: | Bacillariophyceae
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Diatom cells have a unique cell wall made of silica (SiO2). These walls (called "frustules") take many forms, some quite beautiful and ornate. They usually have two asymmetrical sides with a split between them (hence "diatom").
They are one of two great groups of single-celled organisms in the sea. The other is the coccoliths. Since diatoms are made of silica, and coccoliths are made of calcium carbonate, they do not grow in the same places in the sea. This was first discovered by T.H. Huxley in his voyage on HMS Rattlesnake, 1846–1850. Diatoms are also found in some soils and in some waterways on land.
Living diatoms make about 20 to 50 percent of the oxygen produced on the planet each year.[1][2] They take in over 6.7 billion metric tons of silicon each year from the waters in which they live.[3]
Diatom chloroplasts were probably derived from those of red algae. The fossil record of diatoms starts in strata of the Lower Jurassic, ~185 million years ago. Molecular clock evidence suggests an earlier date for their origin.[4] The entire genomes of two species of diatom have been analysed. The analysis reveals that hundreds of genes in both species came from bacteria.[5]
Diatoms have some practical uses. Diatom communities are a popular tool for monitoring environmental conditions, past and present. They are commonly used in studies of water quality. They are also of interest to nanotechnology.
Diatom Media
Dwindling diatoms and the mixed layer Earth's oceans teem with microscopic plants called phytoplankton. But according to a 2015 NASA study, populations of diatoms, the largest type of phytoplankton algae, have declined more than 1 percent per year from 1998 to 2012.3D-animation of the diatom Corethron sp.Displays overlays from four fluorescent channels (a) Green: [DiOC6(3) fluorescence] - stains cellular membranes indicating the core cell bodies(b) Cyan: [PLL-A546 fluorescence] - generic counterstain for visualising eukaryotic cell surfaces(c) Blue: [Hoechst fluorescence] - stains DNA, identifies nuclei(d) Red: [chlorophyll autofluorescence] - resolves chloroplastsThe animation starts by overlaying all available fluorescent channels, and then clarifies the visualisation by switching channels on and off Representation of a diatom - Nucleus; holds the genetic material
- Nucleolus; location of the chromosomes
- Golgi apparatus; modifies proteins and sends them out of the cell
- Cell wall; outer membrane of the cell
- Pyrenoid; center of carbon fixation
- Chromatophore; pigment carrying membrane structure
- Vacuoles; vesicle of a cell that contains fluid bound by a membrane
- Cytoplasmic strands; hold the nucleus
- Mitochondria; create ATP (energy) for the cell
- Valves/Striae; allow nutrients in, and waste out, of the cell
Intricate structures of the diatom - Areolae (hexagonal or polygonal boxlike perforation with a sieve present on the surface of diatom)
- Striae (pores, punctae, spots or dots in a line on the surface)
- Raphe (slit in the valves)
- Central nodule (thickening of wall at the midpoint of raphe)
- Stigmata (holes through valve surface which looks rounded externally but with a slit like internal)
- Punctae (spots or small perforations on the surface)
- Polar nodules (thickening of wall at the distal ends of the raphe)
Selections from Ernst Haeckel's 1904 Kunstformen der Natur (Art Forms of Nature), showing pennate (left) and centric (right) frustules.
Pennate diatom from an Arctic meltpond, infected with two chytrid-like [zoo-]sporangium fungal pathogens (in false-colour red). Scale bar = 10 μm.
References
- ↑ "The air you're breathing? A diatom made that". Live Science. 11 June 2014. Archived from the original on 30 April 2018. Retrieved 30 April 2018.
- ↑ "What are diatoms?". Diatoms of North America. Archived from the original on 25 January 2020. Retrieved 28 January 2020.
- ↑ Treguer, P.; Nelson, D.M.; Van Bennekom, A.J.; Demaster, D.J.; Leynaert, A.; Queguiner, B. (1995). "The silica balance in the world ocean: a reestimate". Science. 268 (5209): 375–9. Bibcode:1995Sci...268..375T. doi:10.1126/science.268.5209.375. PMID 17746543. S2CID 5672525.
- ↑ Kooistra W.H.C.F. and Medlin L.K. 1996. Evolution of the diatoms (Bacillariophyta): IV. A reconstruction of their age from small subunit rRNA coding regions and the fossil record. Mol. Phylogenet. Evol. 6, 391-407.
- ↑ Bowler C. et al. 2008. The Phaeodactylum genome reveals the evolutionary history of diatom genomes. Nature 456: 239–244.