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J Bacteriol. 1973 November; 116(2): 901-907
Copyright © 1973 American Society for Microbiology. All Rights Reserved.

Physiological Studies on the Recovery of Salt Tolerance by Staphylococcus aureus After Sublethal Heating

¹ Food Research Laboratories, Health Protection Branch, Health and Welfare Canada, Ottawa, K1A OL2, Ontario, Canada

ABSTRACT

Cultures of S. aureus in 100 mM potassium phosphate buffer heated at 52 C for 15 min lost their tolerance to 7.5% NaCl. After incubation in a complex growth medium or in a diluted dialyzed medium in which unheated cells were unable to grow, salt tolerance was regained. Heat injury caused 30% loss of lipid. During recovery, the concentration of C₁₅ and C₁₇ fatty acids returned to normal, and there appeared to be an oversynthesis of C₁₆ and C₁₈ unsaturated acids. Penicillin abolished the latter reaction without affecting recovery; chloramphenicol did not affect fatty acid oversynthesis but reduced recovery. The K/Na ratio was 12.6 in control cells and 3.4 in injured cells, where it remained during the recovery of salt tolerance. Aspartate uptake was about 10% of the control level after injury and about 35% at recovery. Control cells grew without a lag on subculture, but injured cells which had regained their salt tolerance needed about 2 more h of incubation. Cells recovering with penicillin needed 6 more h, and cells recovering with chloramphenicol did not grow without a prolonged lag. Cells of S. aureus, therefore, may recover their salt tolerance while various membrane functions are still damaged.