Growth and Fermentation of Bacteria Near Their Minimum Temperature

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Abstract
An attempt was made to consider the minimum temp. of growth separately from that of the energy source, i.e., fermentation. By inoculating sterile milk at 0[degree]C with large numbers of cells of various streptococci, all spp. showed fermentation. The total acid produced was always lowest at 0[degree], larger at 5[degree], still larger at 10 and 15[degree]. No satisfactory explanation for this influence of temp. has been found. With Strep. lactis incapable of growing at 0[degree], the enzyme content of the cells is decreased distinctly by 1 week''s holding at 0[degree], and after 4-8 weeks the cells must grow through several generations before their fermenting capacity becomes normal. With Strep. jecalis, which multiplies at 0[degree], no such injury was observed. The largest bacterial crops were found between the optimum temp. and 10[degree] below this point. The amt. of sugar consumed during the doubling of 1 cell was found constant at low and medium temps.; it increases toward the optimal temp., indicating a more wasteful metabolism. Therefore, lack of available energy does not seem to be the cause of the minimum temp. of growth. Other possible causes are discussed.

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