Isolation and Characteristics of a Halomonas sp. Accumulating Ectoine from Qinghai Lake

Thirty-five strains of halophiles were isolated from 20 water samples of the Qinghai Lake by a RM medium with high salinity.The moderate halophile QHL25 was selected and studied phenotypically,physiologically and phylogenetically.On the basis of its morphological and physiological characteristics,the isolate was round or oval-shaped,white and opaque as a single cell or in clusters.It was a Gram-negative rod that was able to grow at the salt concentration ranging from 0 to 2.9 mol/L(an optimum of 1.45 mol/L).The optimum pH and temperature for growth were 8.5 and 37 ℃ respectively.Based on the 16S rDNA gene sequence analysis,the halophile QHL25 had a 98% similarity with Halomonas sp.K1B-11.According to its morphological,physiological and biochemical characteristics combined with the sequence analysis of the 16S rDNA,strain QHL25 was preliminarily identified as a member of the genus Holomonas,which belonged to Oceanospirillales order of Gammaproteobacteria class.The intracellular compatible solute of ectoine accumulated in QHL25 could be detected by thinlayer chromatography and the content of ectoine was determined as 36.70 mg/g(cell dry weight) by high-performance liquid chromatography in the presence of 1.7 mol/L NaCl.