The response of Lactobacillus acidophilus CRL 639 to cold-shock (freezing) depends on the initial growth temperature. Cells cultured at 25 degrees C (long filaments with a mu value of 0.02 h(-1)) show a higher beta-galactosidase activity and develop cryotolerance, compared with cells grown at 37 degrees C. One-dimensional proteins gel electrophoresis shows the overexpression of six proteins (22.5-105.0 kDa) and the repression of eight proteins (4.3-48.0 kDa) at 25 degrees C.