SUMMARY: The influence of Mg-limitation on the growth of a typical Gram-positive organism——was investigated and the data compared with that obtained with grown under similar conditions. The magnesium contents of both organisms varied with growth rate but were very similar at corresponding growth rates. With Mg-limited chemostat cultures of each organism, uptake of Mg was almost complete at specific growth rates less than 0.7 × maximum. Cellular Mg was tightly bound, none being removed by suspension of the organisms at 20° in 0.85% (w/v) NaCl. When Mg-limited organisms were suspended in environments containing Mg, this ion was rapidly adsorbed; the amount adsorbed varied with both the initial extracellular Mg concentration and the composition of the diluent. had a greater capacity for Mg adsorption than but its affinity for this ion was less. The latter difference correlated with the ability of to outgrow rapidly in Mg-limited chemostat cultures containing both organisms. The significance of these results is discussed in relation to the reports from other laboratories concerning differences between Gram-positive and Gram-negative bacteria in Mg content, uptake of Mg and ability to grow in media of low Mg content.


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