Salinibacter ruber
A Microbial Biorealm page on the genus Salinibacter ruber
Classification
Higher order taxa
cellular organisms; Bacteria; Bacteroidetes/Chlorobi group; Bacteroidetes; Sphingobacteria; Sphingobacteriales; Sphingobacteriales genera incertae sedis; Salinibacter
Species
Salinibacter ruber
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NCBI: Taxonomy |
Description and Significance
Salinibacter ruber is an extremely halophilic red bacteria and was found in saltern crystallizer ponds in Alicante and Mallorca, Spain in 2002 by Anton et al.. This environment has very high salt concentrations, and Salinibacter ruber itself cannot grow below 15% salt concentration, with an ideal concentration between 20-30% (2). Salinibacter ruber survives in this harsh environment because of its adaptations in order to cope with the high salt concentrations. These adaptations are: modifying the sequences of its proteins, recruiting proteins from different sources with different functions, as well as lateral gene transfer from other halophilic organisms (3).
This bacteria is very interesting because of it extremophile tendencies as a bacteria, when this is common mostly in the domain Archaea. Bacteria do not, in general, play a large role in microbial communities of hypersaline brines at or approaching NaCl saturation. However, with the discovery of S. ruber, this belief was weakened. It was found that S. ruber made up from 5% to 25% of the total prokaryotic community of the Spanish saltern ponds! (2)
Salinibacter ruber is most closely related to the genus Rhodothermus which is a thermophilic, slightly halophilic bacteria. Though genetically it is considered to be closest to the Rhodothermus genus, it is most comparable to the family Halobacteriaceae, because of similarity in protein structure.
Genome structure
S. ruber is comprised of a 3,551,823-bp chromosome of high G+C content (66.29%) and a 35,505-bp plasmid (57.9% G+C content). The chromosome contains 2,934 ORFs and the plasmid contains 33. Similar to the Archaea, S. ruber also has regions of low G+C content.
The first of these so-called islands is located 250 kb from the origin of replication. It contains 15 transposases and 5 prophage components, including 3 glycosyl-transferases. The second island is over 55 kb, with 12 transposases and multiple prophage-related ORFs. Additionally, there are some ORFs involved in capsular polysaccharide synthesis. The final G+C island is 39 kb and contains the sole restriction-modification system.
The plasmid codes for 19 hypothetical and conserved hypothetical genes and contains several ORFs involved in DNA metabolism, replication, recombination, as well as a gene involved in UV protection. It also encodes an IS5 family transposon element that is not found in the chromosome. (4)
Within the genome of S. ruber, there is a hypersalinity island, which is extremely crucial for survival in a halophilic environment. This cluster of 19 genes includes a K+ uptake/efflux systems and cationic amino acid transporters. This island is mosaic in nature and is formed by various bacterial and archaeal sources. Many of the genes are similar to those of haloarchaea. Especially important genes in this island are the trkH gene and trkA gene. The Trk system is responsible for the uptake of K+. TrkH is a membrane bound translocating subunit and TrkA is a cytoplasmic membrane surface protein that binds NAD+. There are multiple trkA genes, thus suggesting the complex regulation of this trk system. The overlapping between Salinibacter ruber and members of Archaea suggest lateral gene transfer.
Also within the genome, S. ruber contains 4 rhodopsin genes. 2 are sensory rhodopsin genes, 83 kb apart on the genome. These 2 genes interact in order to produce a color-sensitive photoactive behavior. Also, a sensory rhodopsin is linked to signal transduction genes, which further solidifies the belief that Salinibacter ruber has photosensory function. The final rhodopsin gene identified not only the proton pumping activity of S. ruber, but also a new light-harvesting complex that allows the rhodopsin to have great absorbency.
Cell structure and metabolism
Describe any interesting features and/or cell structures; how it gains energy; what important molecules it produces.
Ecology
S. ruber is found in high salt concentration ponds in Spain. This bacteria has an extremely high salt requirement, which makes it unique among bacteria. Optimum levels of growth are achieved between 2.5 and 3.9 M NaCl, with a minimum of 1.7 M NaCl for any growth at all. This organism is a major component of the microbial community, and as stated before, can be up to 25% of the microbial population. S. ruber requires chloride for growth. This was tested by substituting only 20% of NaCl with gluconate, which ceased growth (6).
Pathology
How does this organism cause disease? Human, animal, plant hosts? Virulence factors, as well as patient symptoms.
Application to Biotechnology
Does this organism produce any useful compounds or enzymes? What are they and how are they used?
Current Research
Enter summaries of the most recent research here--at least three required
References
Edited by student of Rachel Larsen
