Halomonas elongata DSM 2581

Halophilic bacteria and archaea have developed two basically different osmoregulatory mechanisms to cope with ionic strength and the considerable water stress, namely the "salt-in-cytoplasm" mechanism and the organic osmolyte mechanism. Organisms following the salt-in-cytoplasm mechanism adapt the interior protein chemistry of the cell to high salt concentration. The osmotic adjustment of the cell can be achieved by raising the salt concentration (KCl) in the cytoplasm according to the environmental osmolarity. In contrast, microorganisms applying the organic osmolyte mechanism keep their cytoplasm, to a large extent, free of KCl and the design of the cell's interior remains basically unchanged. Instead, organisms of this group accumulate highly water-soluble organic compounds, in order to maintain an osmotic equilibrium with the surrounding medium. These molecules do not disturb the cell's metabolism, even at high cytoplasmic concentrations, and are thus aptly named "compatible solutes". Compatible solutes are beneficial for bacterial cells not only as osmoregulatory solutes, but also as protectants of proteins by mitigating detrimental effects of freezing, drying and high temperatures. The predominant compatible solutes in halophilic bacteria are the amino acid derivatives glycine-betaine and ectoine (1,4,5,6,tetra-2-methyl-4-pyrimidonecarboxylic acid).Halomonas elongata (strain ATCC 33173 / DSM 2581 / NBRC 15536 / NCIMB 2198 / 1H9) is an halophilic Gram-negative bacterium isolated from a solar salt facility. It is halotolerant up to a concentration of 35% and uses ectoine as its major compatible solute. H.elongata can both, synthesize and degrade ectoine. The degradation of ectoine proceeds via hydrolysis of ectoine to -acetyl-L-2,4-diaminobutyric acid, followed by deacetylation to diaminobutyric acid. In H. elongata, diaminobutyric acid can either flow off to aspartate or re-enter the ectoine synthesis pathway, forming a cycle of ectoine synthesis and degradation. Ectoine levels are highly regulated according to external salt levels but the overall picture of its metabolism and control is not well understood. Apart from its critical role in cell adaptation to halophilic environments, ectoine can be used as a stabilizer for enzymes and as a cell protectant in skin and health care applications. Ectoine is produced annually on a scale of tons in an industrial process using H. elongata as producer. (Adapted from PMID: 20849449). (HAMAP: HALED)