The effect of suboptimal growth temperature and growth phase on resistance of Lactobacillus acidophilus to environmental stress

This paper describes the effect: of growth temperature and the physiological age of Lactobacillus acidophilus CRL 639 on the development of cross resistance to different kinds of environmental stress. Exponential-phase cells growing at 25 degrees C and stationary-phase cells (8- and Il-h-old cultures at the optimal temperature of 37 degrees C) showed the highest survival and metabolic activity after challenge by freezing, heating. osmotic stress, and exposure to ethanol, peroxide, or acid. One-dimensional SDS-PAGE gels showed overexpression of three proteins (22.5, 39.6, and 49.2 kDa) at 25 degrees C, of two proteins (40.9 and 48.3 kDa) in 8-h-old cultures, and of one protein (30.3 kDa) after glucose depletion in Il-h-old cultures. These results strongly suggest the involvement of different sets of protein in the cellular processes of adaptation to environmental changes. (C) 1999 Academic Press.