Candidatus gloeomargarita lithophora

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A Microbial Biorealm page on the genus Candidatus gloeomargarita lithophora

Classification

Higher order taxa

Domain (Bacteria); Phylum (Cyanobacteria); Class (Gloeobacteria); Order (Gloeobacterales); Genus (Candidatus Gloeomargarita)¹

Species

Species (lithophora)

Candidatus Gloeomargarita lithophora

Description and significance

Candidatus Gloeomargarita lithophora, a cyanobacterium, was found growing in colonies at the bottom of a lake in Mexico in 2012. This microbe can actively transport elements such as strontium, barium, magnesium, and calcium into the cell from the environment and incorporate them into granules, which increases the density of the cell and helps to keep the bacterium anchored at the bottom of the lake. C.G. lithophora is the first bacterium shown to produce internal biomineralizations, as opposed to other cyanobacteria which can produce external structures as a byproduct of photosynthesis. The mechanism for this biomineralization is still unknown.² It is hypothesized that internal mineralization by this ancient order of cyanobacteria could help explain the lack of fossils from the early origins of cyanobacteria about 2.7 billion years ago, as evidenced by atmospheric oxygen levels, to the earliest fossil evidence of cyanobacteria about 1.2 billion years ago. ³

Genome structure

A genetic analysis of similar bacteria in the Gloeobacter genus found several genes involved in photosynthesis were missing. The bacteria in this genus do not contain a thylakoid membrane, and therefore do not have more advanced structures involved in photosynthesis that are found in other photosynthetic bacteria. This indicates that Gloeobacter is one of the oldest photosynthetic bacteria. The genome for Candidatus Gloeomargarita lithophorahas not yet been studied, but a related microbe, Gloeobacter violaceus, has a single circular chromosome with no plasmid.⁴

Cell and colony structure

Candidatus Gloeomargarita lithophora is a rod-shaped, unicellular microbe measuring about 4 μm long and 1 μ wide.² Theses cells contain around 20 spherical granules within the cytoplasm, each measuring about 270 nm in diameter; these granules comprise roughly 6% of the cell's volume and increase the density of the cell by 12%.This species is also capable of forming biofilms²

Metabolism

Candidatus Gloeomargarita lithophora uses light as an energy source like other cyanobacteria, but unlike other cyanobacteria does not contain thylakoids. A proton gradient forms along the plasma membrane, where phycobilisomes are attached to the cytoplasmic side. C.G. lithophora uses water as an electron donor and produces oxygen as a byproduct. ⁴

Ecology

To date, this microbe has only been found living in shallow water of a freshwater lake, and was later isolated in a lab. As a cyanobacteria, Candidatus Gloeomargarita lithophora is important in oxygen production and carbon fixation. The use of strontium by the cell may lead to the use of the bacterium in remediation of nuclear contamination. ²

References

[1] ["Taxonomy Browser." NCBI. U.S. National Library of Medicine, n.d. Web. 9 Mar. 2013. <http://www.ncbi.nlm.nih.gov/Taxonomy/Browser/wwwtax.cgi?mode=Info>.]

[2] [E. Couradeau , K. Benzerara, E. Gérard, D. Moreira, S. Bernard, G.E. Brown Jr., and P. López-García. “An Early-Branching Microbialite Cyanobacterium Forms Intracellular Carbonates,” Science 336 (2012), 459. DOI: 10.1126/science.1216171]

[3] [R. Riding. "A Hard Life for Cyanobacteria." Science 336 (2012): 427.]

[4] [Y. Nakamura, T. Kaneko, S. Sato, et al. "Complete genome structure of Gloeobacter violaceus PCC 7421, a cyanobacterium that lacks thylakoids". DNA Res. 10 (4): 137–45 (2003)doi: 10.1093/dnares/10.4.137.]

Edited by Andy Nichols, student of Dr. Lisa R. Moore, University of Southern Maine, Department of Biological Sciences, http://www.usm.maine.edu/bio