Adaptation of Pseudomonas fluorescens to Low Levels of Water Activity Produced by Different Solutes1

A culture of Pseudomonas fluorescens which grew at a minimal a w of 0.97 in a glucose-salts broth adjusted to that level with NaCl, KCl, or glucose, and at a w 0.9725 with Na 2 SO 4 , was adapted to grow at lower a w levels produced by these solutes. Adaptation to growth at a low a w produced by means of one solute did not necessarily result in growth at that a w when another solute was employed to lower the a w . The culture adapted to grow at a w 0.9650 produced by addition of glucose could grow equally well in broth adjusted to that a w with NaCl or KCl, but not Na 2 SO 4 . NaCl and KCl permitted growth at the lowest a w level (0.9625), and the culture adapted in KCl did equally well in NaCl.