Damage to Streptococcus lactis resulting from growth at low pH.

Harvey, R. J. (The Dairy Research Institute, Palmerston North, New Zealand). Damage to Streptococcus lactis resulting from growth at low pH. J. Bacteriol. 90:1330-1336. 1965.-Growth of Streptococcus lactis below pH 5.0 results in damage to the cells. A period of growth below pH 5.0 is required before this damage is expressed, and a period of growth above pH 5.0 is required to correct the damage. Part of the damage consists of a reduction in the specific activities of a number of enzymes. At the same time, the differential rate of total protein synthesis is unchanged. During recovery from growth at low pH, the enzymes subject to damage are formed at a differential rate which is higher than normal until the normal specific activities are restored. The growth rate characteristic of the new pH is then resumed. The results are consistent with either of two mechanisms of damage. Growth at low pH could result either in direct inactivation of a number of enzymes, or in loss of control of the differential rates of synthesis of individual enzymes.