Date of Award
Master of Science
J. Orvin Mundt
John Woodward, David Bemis
The ability of Clostridium sprogenes to adapt to growth at low pH was studied in tomato serum prepared by enzymatic hydrolysis of canned tomatoes and tomato juice. The lowest pH at whicn C. sporogenes could grow before adaptation in tomato serum, Trypticase Peptone Glucose Yeast Extract (TPGY) and fluid thioglycollate broths was pH 5.4.
Tomato serum and TPGY or fluid thioglycollate broth adjusted to varying pH levels were inoculated with C. sporogenes from tubes with growth at the lower pH values. Subsequent transfers of C. sporogenes grown in tomato serum were made to tomato serum of equal and lower pH values. Strains emerged which were capable of initiating growth in tomato serum having a pH as low as 4.85. The adaptation to growth at low pH could be maintained only by continuous subculture at pH 5.0. The ability to grow in tomato serum having pH 5.0 was lost after one passage through neutral media at pH 6.9-7.0.
After storage at 4.4°C, cultures grown in tomato serum at pH 5.0 grew in tomato serum at pH 5.0 if subcultured within 7 days, but not after 21 days.
The addition of mineral salts (FeSO4, CuSO4,ZnSO4, MnSO4, and MgC12) and components of TPGY medium (sodium thioglycollate, trypticase, peptone, glucose and yeast extract) to tomato serum did not result in growth at pH values below that obtained in tomato serum alone.
Crosthwait, Claudia Dee, "Adaptation to Growth at Low pH by Clostridium sporogenes. " Master's Thesis, University of Tennessee, 1979.