The extremely halophilic bacterium Salinibacter ruber inhabits saltern crystallizer ponds worldwide, together with the square archaeon Haloquadratum walsbyi. Cultures of Salinibacter have been shown to convert up to 20% of the glycerol added to a not previously characterized overflow product. We here identify this product of incomplete glycerol oxidation by Salinibacter as dihydroxyacetone. Genomic information suggests that H. walsbyi possesses an efficient uptake system for dihydroxyacetone, and we show here that dihydroxyacetone is indeed metabolized by Haloquadratum cultures, as well as by the heterotrophic prokaryotic community of the saltern crystallizer ponds in Eilat, Israel, dominated by Haloquadratum-like cells. In the absence of glycerol, Salinibacter also takes up dihydroxyacetone. Degradation of glycerol, produced in hypersaline lakes as an osmotic solute by the green alga Dunaliella salina may thus involve dihydroxyacetone as an intermediate, which can then be taken up by different types of heterotrophs present in the environment.
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Acknowledgments We thank Mike Dyall-Smith and David Burns (Melbourne) for their gift of the Haloquadratum culture, and Lily Mana and Polina Khristo for their assistance in part of the experiments. We are further grateful to the Israel Salt Company in Eilat, Israel for allowing access to the salterns, and to the staff of the Interuniversity Institute for Marine Sciences of Eilat for logistic support. This study was supported by the Israel Science Foundation (grant no. 617/07).
- Incomplete oxidation