FURTHER MINERAL REQUIREMENTS OF STREPTOCOCCUS FAECALIS

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Abstract
By applying a biological purification procedure to a complex medium to remove contaminating traces of inorganic ions, MacLeod and Snell, in a previous study were able to demonstrate certain of the mineral requirements of the lactic acid bacteria. In the present study an attempt was made to demonstrate further mineral requirements of the same organisms by applying the same purification procedure to a more highly purified medium, one containing crystalline amino acids in place of the enzymatic casein hydrolysate. For only one of the organisms studied, S. faecalis R, ATCC 8043, could further mineral requirements be demonstrated. When this organism was permitted to grow in a medium containing no added Mg++ and the cells were centrifuged out, no further growth of the organism would take place in the medium on reinoculation unless Mg++ was added back. Similarly a medium containing an excess of Mg++ but no added Mn++ when treated in the same way supported adequate growth only upon the addition of Mn++. A number of related ions tested were found to be unable to replace Mn and Mg++ in the nutrition of the organism. Mn++ could be shown to exert a sparing action of the requirements for Mg++. Citrate interfered with the response of S. faecalis to Mg++ only at levels of Mg++ in-sufficient for maximum growth in the absence of citrate. Cultures of S. faecalis grown in the presence of suboptimal concns. of Mg++ and Mn++ autolysed at the greatly increased rate. This increase in the rate of autolysis could be prevented completely by the addition of small amts. of Mn++ and partially by the addition of relatively large amts. of Mg++ to the medium. Lack of Mn++ and Mg++ in the medium had no effect upon the Gram staining characteristics of the organism.