Calcium Uptake during Growth of Streptococcus lactis

Abstract

WHEN the protein antibiotic nisin is extracted from cells with acids which also precipitate Ca⁺⁺—for example, sulphuric and oxalic acids—there is a loss of 75–80 per cent of biological activity (preceding communication). The same loss is not observed when the isolated material is dissolved in the same solvents, which suggests that the protein is bound to the cell as a calcium complex which is irreversibly altered when the antibiotic is extracted. Although a number of reference books make the general statement that cells require Ca⁺⁺ or that Ca⁺⁺ is required for phage adsorption, there seems to be no published work on the Ca⁺⁺ content of Streptococci. Nurumikko and Karka^1,2 observed that Ca⁺⁺ is essential for growth in Streptococcus thermophilus and we now describe the concentration of Ca⁺⁺ during the growth cycle of S. lactis. We found that high cellular concentrations of Ca⁺⁺ occur during the lag phase which correspond with apparent low nisin content. During stationary phase Ca⁺⁺ content is low and the cellular nisin content is high.