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Investigations of the calcium and magnesium metabolism of marine deaminating bacteria have revealed that these organisms are capable of binding alkaline-earth elements on or in the cell wall-cell membrane complex. In actively metabolizing cells, both calcium and magnesium are taken up as a complex with amino acids and peptone. Accumulation of these elements during this phase, however, is low as compared with senescent cells. In the latter case, the accumulation of calcium is such that a given volume of cells will concentrate up to 100 × the concentration in an equivalent volume of sea water. Magnesium concentration is considerably less and the element appears to be preferentially exchanged for calcium at this stage.
The nature of the binding force is under investigation but appears to be a type of weak adsorption or ion exchange. The bound calcium may be eluted from cells by washing with any isotonic fluid at pH's varying between 5 and 9.
Unwashed cells may be considered as small concentrated sources of calcium. When carbonate concentration becomes sufficiently high (from respired C02) and pH is at a minimum of 7.8 (from excretion of NH3), calcium carbonate precipitation occurs as aragonite crystals with bacteria occupying the center of the crystal. It is surmised that bacteria may act as nuclei for precipitation in nature since the environment produced in static culture in the laboratory is similar to that produced in interstitial spaces of the upper sediments-only on a smaller scale. Examination of fine sediment particles from Florida Bay have revealed them to be largely calcified bacteria.
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