We have examined the organic osmotic solutes content within the stratified microbial communities in an evaporitic gypsum crust found in an evaporation pond (~194 g/l total dissolved salts) of the salterns of the Israel Salt Company, Eilat. We extracted intracellular solutes from the upper three pigmented layers of the crust: a yellow-orange layer dominated by unicellular cyanobacteria, a green layer with filamentous cyanobacteria, and a layer colored red-purple by purple sulfur bacteria; dense communities of heterotrophic bacteria were present in all layers. The solutes were analyzed by Raman spectroscopy, 1H and 13C nuclear magnetic resonance, and HPLC. All layers contained glycine betaine as the only detectable osmotic solute; ectoine and other solutes known to be produced by many halophilic and halotolerant prokaryotes were not found. In this first attempt to assess the osmotic solute content within complex natural communities of halophilic microorganisms, the predominant role of glycine betaine as an osmolyte was established. Most heterotrophic bacteria cannot produce glycine betaine but preferentially use it when it is supplied. Presence of glycine betaine produced by the photoautotrophic members of the community, therefore, may relieve the heterotrophs from the need to synthesize other compounds at a high-energy cost.
Bibliographical noteFunding Information:
(to AO and ZA) and by Grant No. P210/10/0467 from the Grant Agency of the Czech Republic and institutional support MSM0021620855 from the Ministry of Education of the Czech Republic (to JJ).
Acknowledgments We thank Lily Mana for her assistance during the experiments, the Israel Salt Company in Eilat, Israel for allowing access to the salterns, and the staff of the Interuniversity Institute for Marine Sciences of Eilat for logistic support. This study was supported by Grant No. 1103/10 from the Israel Science Foundation
- Compatible solutes
- Raman spectroscopy