Accumulation and role of compatible solutes in fast-growing Salinivibrio costicola subsp. yaniae.

The moderately halophilic bacterium Salinivibrio costicola subsp. yaniae showed an extremely fast growth rate. Optimal growth was observed in artificial seawater containing 1.4 mol/L NaCl and in MM63 media containing 0.6 mol/L NaCl. We analyzed a variety of compatible solutes that had accumulated in this strain grown in the media. The supplementation effect of the compatible solutes glycine betaine, glutamate, and ectoine to the growth of S. costicola subsp. yaniae was examined. Glycine betaine and glutamate had no supplementation effect on the fast growth rate. Growth of salt-sensitive mutants MU1 and MU2, both of which were defective in the ability to synthesize ectoine, was not observed in MM63 medium in the presence of more than 1.0 mol/L NaCl. From these data, we conclude that ectoine was the predominant compatible solute synthesized in this bacterium that effected an extremely fast growth rate.