Salinarchaeum laminariae

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Classification

Archaea, Euryarchaeota, Halobacteria, Halobacteriales, Halobacteriaceae


Species

Salinarchaeum laminariae

Description and Significance

Salinarchaeum laminariae is a gram-negative halophilic archaea in the shape of pleomorphic rods. It is mesophilic, growing between 20 and 50°C with an optimum growth temperature of 37°C. S. laminariae will lyse in distilled water. A minimum sodium chloride concentration of 8 to 12 % is required to maintain cellular integrity. It will grow in a pH range of 5.5 to 9.5. Optimal growth is achieved with a pH range of 7 to 7.5. This is the model organism for the genus Salinarchaeum.

S. Laminariae was isolated from the brine of the commercially cultivated seaweed, Laminaria japonica. This seaweed is preserved by salting and storage at temperatures below freezing. When returned to room temperatures, the seaweed turns red and begins to rot. Halophiles from the family Halobacteriaceae are noted for forming red pigments. Viable cells from this family have been isolated from salt crystals and successfully cultured. It is suspected that S. Laminariae, along with other members of halobacteriaceae, is causing the spoilage of commercially packaged seaweed after introduction through the salt crystals used in the brining process.

Genome Structure

Two strains of Salinarchaeum laminariae, R26T and R22, were reported. Their 16S rRNA sequences were 99.9% similar and their DNA-DNA hybridization value was 89%. Justification for the establishment of the genus Salinarchaeum was provided by analyzing the rpoβ’ gene, which codes for the β subunit of RNA polymerase. Both strains had a rpoβ’ gene length of 1830 base pairs and were 99.5% similar. The G+C content of the strains were 65.8 and 66.4 %mol, respectively.

The genome of S. laminariae is most similar to Natronoarchaeum mannanilyticum, a halophilic archaea isolated from commercial salt crystals made from Japanese seawater. A comparison of their 16S rRNA sequences reveals a 90.2 – 90.6% similarity. Phylogenetic analysis showed that these two organisms form a distinct clade.

Cell Structure, Metabolism and Life Cycle

The cell membrane of S. laminariae contains phosphatidylglycerol (PG) and phosphatidylglycerol phosphate methyl ester (PG-Me), which are common among members of the family Halobacteriaceae (Kamekara 1999). It also contains phosphatidylglycerol sulfate. The membrane has not been found to contain glycolipids. Lipid profiles are one of the key factors used to distinguish genera within halobacteriaceae.

S. laminariae is a heterotrophic obligate aerobe that obtains energy and carbon through the oxidation of sugars. It can also obtain energy, carbon, and carbon from the amino acid L-glutamate.

The red color associated with members of halobacteriaceae is a result of membrane bound pigments such a bacteriorhodopsin and carotenoids that are able to capture high energy photons that would otherwise be capable of causing photooxidative damage.

Ecology and Pathogenesis

Habitat; symbiosis; biogeochemical significance; contributions to environment.
If relevant, how does this organism cause disease? Human, animal, plant hosts? Virulence factors, as well as patient symptoms.

References

[Sample reference] Takai, K., Sugai, A., Itoh, T., and Horikoshi, K. "Palaeococcus ferrophilus gen. nov., sp. nov., a barophilic, hyperthermophilic archaeon from a deep-sea hydrothermal vent chimney". International Journal of Systematic and Evolutionary Microbiology. 2000. Volume 50. p. 489-500.

Author

Page authored by _____, student of Prof. Jay Lennon at Michigan State University.

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