The effect of abrupt changes in sodium chloride concentration upon the viability of gram-negative bacteria at 2 and 40 degrees C

“Osmotic” shock between 0.14 m and 4.5 m NaCl is highly temperature dependent for postlog populations of E. coli, A. aerogenes, and P. aeruginosa, suggesting that killing is not due solely to simple physical osmotic action. Thermal shock in postlog E. coli and A. aerogenes does not occur, although in P. aeruginosa populations when temperature fluctuations are repetitious appreciable loss of viability does occur. Thermal shock concomitant with osmotic shock, on the other hand, is lethal to postlog populations of all 3 species. Thus, during freezing-thawing concentrated solute is a prime candidate for causing death in postlog E. coli, A. aerogenes, and P. aeruginosa populations.