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

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.