Scytonema crispum

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A Microbial Biorealm page on the genus Scytonema crispum

Classification

Bacteria; Cyanobacteria; Hormogoneae; Nostocales; Scytonemataceae; Scytonema; Scytonema crispum

Description and significance

Scytonema crispum is part of the genus Scytonema which belongs to the phyla Cyanobacteria. S. crispum is a filamentous aquatic bacterium and can be found in fresh water environments. S. crispum is important ecologically because it has the ability to fix nitrogen from the environment. Because of this, scytonema can also form symbiotic relationships with other organisms such as fungi. The genus scytonema is especially important because these bacterium have been found to produce special chemicals such as toxins. In 2003 an anti-HIV protein, scytovirin, was isolated from a bacterial species of Scytonema.

Genome structure

The genome length of scytonema is about 11,953 kb, the largest of all cyanobacteria.

Cell structure, metabolism & life cycle

Scytonema reproduce by hormogonia, which develop at the ends of branches and bud from sheaths. Hormogonia germinate at both ends and form isopolar filaments. Scytonema crispum fixes nitrogen, thus providing nitrogen to the leaves of plants on which it is growing o.n This allows for some symbiotic relationships to be established with other organisms. Within scytonema's filamentous cells are heterocysts which are structures without oxygen that allow the enzyme nitrogenase to fix atmospheric nitrogen into ammonium.

Ecology (including pathogenesis)

Scytonema species, including s.crispum are mostly aquatic organisms that are free-floating, grow attached to a submerged substrate, or grow in filaments that form dark mats. Scytonema also grow on rocks, wood, soil, and plants. S. crispum is found to be growing in mostly fresh-water environments.

Interesting feature

One interesting feature of s. crispum is that it has most recently been discovered to be the first species of Scytonema to produce saxitoxins, which are fast-acting neurotoxins that inhibit nerve conduction by blocking sodium channels. The specific s. crispum that was isolated in this experiment was found in freshwater off the coast of New Zealand.

References

[http://web.ebscohost.com/ehost/detail?vid=4&hid=112&sid=12837370-1f98-48a1-a864-e7f977a7d5dd%40sessionmgr111&bdata=JnNpdGU9ZWhvc3QtbGl2ZQ%3d%3d#db=a9h&AN=9345104. Bokesch, Heidi R. O'Keefe, B., McKee, T., Pannell, L., Patterson, G., Gardella, R., Sowder, R., Turpin, J., Watson, K., Buckheit, R., Boyd, M. A Potent Novel Anti-HIV Protein from the Cultured Cyanobacterium Scytonema varium. Biochemistry. 2003. Volume 42. p. 2578.]

First report of saxitoxin production by a species of the freshwater benthic cyanobacterium, Scytonema. Smitha F., Wood, S., Ginkel, R., Broady, R., Gawa, S. Toxicon. 2010. Volume 57. P. 566-573

Genome Size and SSU rDNA Copy Number: Estimation of Microbial Relative Abundance from a Mixed Population. Fogel, G.B, Collins, C.R., Li, J., Brunk, C.F. Microbial Ecology Volume 38. p. 93-113