A PROMINENT ROLE FOR GLUCOSYLGLYCEROL IN THE ADAPTATION OF PSEUDOMONAS-MENDOCINA-SKB70 TO OSMOTIC-STRESS

The mechanism of osmoadaptation in a salt-tolerant (1.2 M NaCl) bacter ial isolate identified as Pseudomonas mendocina (N. J. Palleroni, M. D oudoroff, R. Y. Stanier, R. E. Solanes, and R. Mandel, J. Gen. Microbi ol. 60:215-231, 1970) was investigated. In response to osmotic stress, this species accumulated a number of compatible solutes, the intracel lular levels of,which depended on both the osmolarity and the ionic co mposition of the growth medium. Glucosylglycerol [alpha-D-glucopyranos yl-alpha-(1-->2)-glycerol], N-acetylglutaminylglutamine amide, and L-a lpha-glutamate were the major compatible solutes accumulated via de no vo biosynthesis. Trehalose was also accumulated, but only in cells gro wn in the presence of high concentrations of sulfate or phosphate ions . Glycine betaine was accumulated only when supplied exogenously to ce lls grown at high osmolarity, and its accumulation caused a significan t depletion of the intracellular pools of glucosylglycerol and glutama te. Glucosylglycerol was also found to accumulate in the type strains of P. mendocina and P. psendoalcaligenes. This is the first report dem onstrating the pivotal role of glucosylglycerol in osmoadaptation in a nonphotosynthetic microorganism.