Editing Cyanobacteria (section)

== Movement ==
[[File:Cyanobacteriaunicellularandcolonial020 Synechococcus.jpg|thumb|upright=1| ''[[Synechococcus]]'' uses a gliding technique to move at 25 μm/s. Scale bar is about 10 μm.]]
{{further|Cyanobacterial movement|Bacterial motility}}

It has long been known that [[filamentous cyanobacteria]] perform surface motions, and that these movements result from [[type IV pili]].<ref>{{cite journal | vauthors = Duggan PS, Gottardello P, Adams DG | title = Molecular analysis of genes in Nostoc punctiforme involved in pilus biogenesis and plant infection | journal = Journal of Bacteriology | volume = 189 | issue = 12 | pages = 4547–4551 | date = June 2007 | pmid = 17416648 | pmc = 1913353 | doi = 10.1128/JB.01927-06 }}</ref><ref name="Khayatan2015"/><ref>{{cite journal | vauthors = Wilde A, Mullineaux CW | title = Motility in cyanobacteria: polysaccharide tracks and Type IV pilus motors | journal = Molecular Microbiology | volume = 98 | issue = 6 | pages = 998–1001 | date = December 2015 | pmid = 26447922 | doi = 10.1111/mmi.13242 | doi-access = free }}</ref> Additionally, ''[[Synechococcus]]'', a marine cyanobacteria, is known to swim at a speed of 25 μm/s by a mechanism different to that of bacterial flagella.<ref>{{cite journal | vauthors = Waterbury JB, Willey JM, Franks DG, Valois FW, Watson SW | title = A cyanobacterium capable of swimming motility | journal = Science | volume = 230 | issue = 4721 | pages = 74–76 | date = October 1985 | pmid = 17817167 | doi = 10.1126/science.230.4721.74 | bibcode = 1985Sci...230...74W }}</ref> Formation of waves on the cyanobacteria surface is thought to push surrounding water backwards.<ref>{{cite journal | vauthors = Ehlers K, Oster G | title = On the mysterious propulsion of Synechococcus | journal = PLOS ONE | volume = 7 | issue = 5 | pages = e36081 | year = 2012 | pmid = 22567124 | pmc = 3342319 | doi = 10.1371/journal.pone.0036081 | doi-access = free | bibcode = 2012PLoSO...736081E }}</ref><ref name=Miyata2020>{{cite journal | vauthors = Miyata M, Robinson RC, Uyeda TQ, Fukumori Y, Fukushima SI, Haruta S, Homma M, Inaba K, Ito M, Kaito C, Kato K, Kenri T, Kinosita Y, Kojima S, Minamino T, Mori H, Nakamura S, Nakane D, Nakayama K, Nishiyama M, Shibata S, Shimabukuro K, Tamakoshi M, Taoka A, Tashiro Y, Tulum I, Wada H, Wakabayashi KI | display-authors = 6 | title = Tree of motility - A proposed history of motility systems in the tree of life | journal = Genes to Cells | volume = 25 | issue = 1 | pages = 6–21 | date = January 2020 | pmid = 31957229 | pmc = 7004002 | doi = 10.1111/gtc.12737 }} {{Creative Commons text attribution notice|cc=by4|from this source=yes}}</ref> Cells are known to be [[motile]] by a gliding method<ref>{{cite book | vauthors = Castenholz RW |year=1982 |chapter=Motility and taxes | veditors = Carr NG, Whitton BA |title=The biology of cyanobacteria |publisher=University of California Press, Berkeley and Los Angeles |pages=413–439 |isbn=978-0-520-04717-4}}</ref> and a novel uncharacterized, non-phototactic swimming method<ref>{{cite journal | vauthors = Waterbury JB, Willey JM, Franks DG, Valois FW, Watson SW | title = A cyanobacterium capable of swimming motility | journal = Science | volume = 230 | issue = 4721 | pages = 74–76 | date = October 1985 | pmid = 17817167 | doi = 10.1126/science.230.4721.74 | name-list-style = amp | bibcode = 1985Sci...230...74W }}</ref> that does not involve flagellar motion.

Many species of cyanobacteria are capable of gliding. [[Gliding motility|Gliding]] is a form of cell movement that differs from crawling or swimming in that it does not rely on any obvious external organ or change in cell shape and it occurs only in the presence of a [[substrate (biology)|substrate]].<ref>{{cite journal | vauthors = McBride MJ | title = Bacterial gliding motility: multiple mechanisms for cell movement over surfaces | journal = Annual Review of Microbiology | volume = 55 | pages = 49–75 | year = 2001 | issue = 1 | pmid = 11544349 | doi = 10.1146/annurev.micro.55.1.49 }}</ref><ref>{{cite journal | vauthors = Reichenbach H | title = Taxonomy of the gliding bacteria | journal = Annual Review of Microbiology | volume = 35 | pages = 339–364 | year = 1981 | issue = 1 | pmid = 6794424 | doi = 10.1146/annurev.mi.35.100181.002011 }}</ref> Gliding in filamentous cyanobacteria appears to be powered by a "slime jet" mechanism, in which the cells extrude a gel that expands quickly as it hydrates providing a propulsion force,<ref>{{cite journal | vauthors = Hoiczyk E, Baumeister W | title = The junctional pore complex, a prokaryotic secretion organelle, is the molecular motor underlying gliding motility in cyanobacteria | journal = Current Biology | volume = 8 | issue = 21 | pages = 1161–1168 | date = October 1998 | pmid = 9799733 | doi = 10.1016/S0960-9822(07)00487-3 | doi-access = free | bibcode = 1998CBio....8.1161H }}</ref><ref>{{cite journal | vauthors = Hoiczyk E | title = Gliding motility in cyanobacterial: observations and possible explanations | journal = Archives of Microbiology | volume = 174 | issue = 1–2 | pages = 11–17 | year = 2000 | pmid = 10985737 | doi = 10.1007/s002030000187 | bibcode = 2000ArMic.174...11H }}</ref> although some [[unicellular]] cyanobacteria use [[type IV pili]] for gliding.<ref>{{cite journal | vauthors = Bhaya D, Watanabe N, Ogawa T, Grossman AR | title = The role of an alternative sigma factor in motility and pilus formation in the cyanobacterium Synechocystis sp. strain PCC6803 | journal = Proceedings of the National Academy of Sciences of the United States of America | volume = 96 | issue = 6 | pages = 3188–3193 | date = March 1999 | pmid = 10077659 | pmc = 15917 | doi = 10.1073/pnas.96.6.3188 | doi-access = free | bibcode = 1999PNAS...96.3188B }}</ref><ref name="Tamulonis2011" />

Cyanobacteria have strict light requirements. Too little light can result in insufficient energy production, and in some species may cause the cells to resort to heterotrophic respiration.<ref name="Stal2000book" /> Too much light can inhibit the cells, decrease photosynthesis efficiency and cause damage by bleaching. UV radiation is especially deadly for cyanobacteria, with normal solar levels being significantly detrimental for these microorganisms in some cases.<ref name=Donkor1991>{{cite journal | vauthors = Tamulonis C, Postma M, Kaandorp J | title = Modeling filamentous cyanobacteria reveals the advantages of long and fast trichomes for optimizing light exposure | journal = PLOS ONE | volume = 6 | issue = 7 | pages = e22084 | year = 2011 | pmid = 21789215 | pmc = 3138769 | doi = 10.1371/journal.pone.0022084 | doi-access = free | bibcode = 2011PLoSO...622084T }}</ref><ref name=Donkor1993>{{cite journal |doi=10.1111/j.1574-6941.1993.tb00026.x |title=Effects of tropical solar radiation on the motility of filamentous cyanobacteria |year=1993 | vauthors = Donkor VA, Amewowor DH, Häder DP |journal=FEMS Microbiology Ecology |volume=12 |issue=2 |pages=143–147 |bibcode=1993FEMME..12..143D |doi-access=free}}</ref><ref name=Tamulonis2011 />

Filamentous cyanobacteria that live in microbial mats often migrate vertically and horizontally within the mat in order to find an optimal niche that balances their light requirements for photosynthesis against their sensitivity to photodamage. For example, the filamentous cyanobacteria ''[[Oscillatoria]]'' sp. and ''[[Spirulina (genus)|Spirulina subsalsa]]'' found in the hypersaline benthic mats of [[Guerrero Negro]], Mexico migrate downwards into the lower layers during the day in order to escape the intense sunlight and then rise to the surface at dusk.<ref>{{cite journal | vauthors = Garcia-Pichel F, Mechling M, Castenholz RW | title = Diel Migrations of Microorganisms within a Benthic, Hypersaline Mat Community | journal = Applied and Environmental Microbiology | volume = 60 | issue = 5 | pages = 1500–1511 | date = May 1994 | pmid = 16349251 | pmc = 201509 | doi = 10.1128/aem.60.5.1500-1511.1994 | bibcode = 1994ApEnM..60.1500G }}</ref> In contrast, the population of ''Microcoleus chthonoplastes'' found in hypersaline mats in [[Camargue]], France migrate to the upper layer of the mat during the day and are spread homogeneously through the mat at night.<ref>{{cite journal | vauthors = Fourçans A, Solé A, Diestra E, Ranchou-Peyruse A, Esteve I, Caumette P, Duran R | title = Vertical migration of phototrophic bacterial populations in a hypersaline microbial mat from Salins-de-Giraud (Camargue, France) | journal = FEMS Microbiology Ecology | volume = 57 | issue = 3 | pages = 367–377 | date = September 2006 | pmid = 16907751 | doi = 10.1111/j.1574-6941.2006.00124.x | bibcode = 2006FEMME..57..367F | doi-access = free }}</ref> An in vitro experiment using ''[[Phormidium|Phormidium uncinatum]]'' also demonstrated this species' tendency to migrate in order to avoid damaging radiation.<ref name=Donkor1991 /><ref name=Donkor1993 /> These migrations are usually the result of some sort of photomovement, although other forms of taxis can also play a role.<ref>{{cite journal | vauthors = Richardson LL, Castenholz RW | title = Diel Vertical Movements of the Cyanobacterium Oscillatoria terebriformis in a Sulfide-Rich Hot Spring Microbial Mat | journal = Applied and Environmental Microbiology | volume = 53 | issue = 9 | pages = 2142–2150 | date = September 1987 | pmid = 16347435 | pmc = 204072 | doi = 10.1128/aem.53.9.2142-2150.1987 | bibcode = 1987ApEnM..53.2142R }}</ref><ref name=Tamulonis2011 />

Photomovement – the modulation of cell movement as a function of the incident light – is employed by the cyanobacteria as a means to find optimal light conditions in their environment. There are three types of photomovement: photokinesis, phototaxis and photophobic responses.<ref name="Häder1987">{{cite journal |doi=10.1111/j.1751-1097.1987.tb04745.x |title=EFFECTS OF UV-B IRRADIATION ON PHOTOMOVEMENT IN THE DESMID, Cosmarium cucumis |year=1987 | vauthors = Häder DP |journal=Photochemistry and Photobiology |volume=46 |issue=1 |pages=121–126 }}</ref><ref>{{cite journal | vauthors = Nultsch W, Häder DP | title = Photomovement in motile microorganisms--II | journal = Photochemistry and Photobiology | volume = 47 | issue = 6 | pages = 837–869 | date = June 1988 | pmid = 3064112 | doi = 10.1111/j.1751-1097.1988.tb01668.x | doi-access = free }}</ref><ref>{{cite book |doi=10.1201/9780203495902-126 |chapter=Photomovements of Microorganisms: An Introduction |title=CRC Handbook of Organic Photochemistry and Photobiology |date=2003 |pages=2393–2402 |publisher=CRC Press |isbn=978-0-429-20964-2 |editor1-first=William M. |editor1-last=Horspool |editor2-first=Francesco |editor2-last=Lenci }}</ref><ref name=Tamulonis2011 />

Photokinetic microorganisms modulate their gliding speed according to the incident light intensity. For example, the speed with which ''Phormidium autumnale'' glides increases linearly with the incident light intensity.<ref>{{cite journal |last1=Nultsch |first1=Wilhelm |title=DER EINFLUSS DES LICHTES AUF DIE BEWEGUNG DER CYANOPHYCEEN: III. Mitteilung: PHOTOPHOBOTAXIS VON PHORMIDIUM UNCINATUM |journal=Planta |date=1962 |volume=58 |issue=6 |pages=647–663 |doi=10.1007/BF01914754 |jstor=23364646 |bibcode=1962Plant..58..647N }}</ref><ref name=Tamulonis2011 />

Phototactic microorganisms move according to the direction of the light within the environment, such that positively phototactic species will tend to move roughly parallel to the light and towards the light source. Species such as ''Phormidium uncinatum'' cannot steer directly towards the light, but rely on random collisions to orient themselves in the right direction, after which they tend to move more towards the light source. Others, such as ''[[Anabaena variabilis]]'', can steer by bending the [[trichome]].<ref>{{cite journal |doi=10.1007/BF00408050 |title=Investigations on the phototactic orientation of Anabaena variabilis |year=1979 | vauthors = Nultsch W, Schuchart H, Höhl M |journal=Archives of Microbiology |volume=122 |issue=1 |pages=85–91 |bibcode=1979ArMic.122...85N }}</ref><ref name=Tamulonis2011 />

Finally, photophobic microorganisms respond to spatial and temporal light gradients. A step-up photophobic reaction occurs when an organism enters a brighter area field from a darker one and then reverses direction, thus avoiding the bright light. The opposite reaction, called a step-down reaction, occurs when an organism enters a dark area from a bright area and then reverses direction, thus remaining in the light.<ref name=Tamulonis2011 />

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