The complete genome sequence of Rhodobaca barguzinensis alga05 (DSM 19920) documents its adaptation for life in soda lakes
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Soda lakes, with their high salinity and high pH, pose a very challenging environment for life. Microorganisms living in these harsh conditions have had to adapt their physiology and gene inventory. Therefore, we analyzed the complete genome of the haloalkaliphilic photoheterotrophic bacterium Rhodobaca barguzinensis strain alga05. It consists of a 3,899,419 bp circular chromosome with 3624 predicted coding sequences. In contrast to most of Rhodobacterales, this strain lacks any extrachromosomal elements. To identify the genes responsible for adaptation to high pH, we compared the gene inventory in the alga05 genome with genomes of 17 reference strains belonging to order Rhodobacterales. We found that all haloalkaliphilic strains contain the mrpB gene coding for the B subunit of the MRP Na+/H+ antiporter, while this gene is absent in all non-alkaliphilic strains, which indicates its importance for adaptation to high pH. Further analysis showed that alga05 requires organic carbon sources for growth, but it also contains genes encoding the ethylmalonyl-CoA pathway for CO2 fixation. Remarkable is the genetic potential to utilize organophosphorus compounds as a source of phosphorus. In summary, its genetic inventory indicates a large flexibility of the alga05 metabolism, which is advantageous in rapidly changing environmental conditions in soda lakes.
KeywordsElement cycles Genome annotation Haloalkaliphiles Rhodobacterales Soda lake
The authors are beholden to Dr. Katya Boldareva-Nuyanzina for providing her strain Rca. barguzinensis strain alga05. We also thank Jason Dean B.Sc. for the language revision. We thank Simone Severitt and Nicole Heyer for excellent technical assistance. This research has been supported by the GAČR project P501/12/G055, the DAAD project 57155424, and the MŠMT project Algatech Plus (LO1416). J.T. was supported by the Deutsche Forschungsgemeinschaft (DFG) within the Transregio 51 “Roseobacter”.
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