Moderately Halophilic Bacterium Halomonas sp. AAD12: A Promising Candidate as a Hydroxyectoine Producer

Abstract

Properties of osmolytes that help protect biological molecules from stress and preserve their functions impose significant importance to finding new organisms with different osmolyte accumulation strategies. To this end, the moderately halophilic Halomonas sp. AAD12 has been characterized for its adaptation to stress conditions with particular emphasis on its osmolyte accumulation strategy. The effect of temperature, salinity, aeration and organic components on the accumulation of osmoprotectants and synthesis of fatty acids were examined in M63 minimal medium. Ectoine, proline and hydroxyectoine were the major osmolytes and palmitic acid (16:0), palmitoleic acid (16:1), and oleic acid (18:1) were the major fatty acids. Overall, ectoine yield was the highest among the three osmolytes at all salt concentrations and temperatures investigated. However, high salinity reduced ectoine yield with a concomitant increase in hydroxyectoine yield. The yield of hydroxyectoine as high as 525 mol/g dry cell mass at 37°C suggested that this microorganism could be a promising candidate as a hydroxyectoine producer.

Microbial Diversity in Extreme Marine Habitats and Their Biomolecules

“…Some extremely halophilic bacteria accumulate inorganic ions (K + , Na + , and Cl − ) in the cytoplasm, which is a type of “salt-in” strategy to balance the osmotic pressure of the environment. Moreover, they have also developed specific proteins that are stable and active in the presence of salts [175,176,177,178]. The stability of the enzymes depends on the negative charge on the surface of the protein due to acidic amino acids, the hydrophobic groups in the presence of high salt concentrations and the hydratation of the protein surface due to the carboxylic groups that are present in aspartic and glutamic acids [179].…”