The Utilization of Magnesium by Certain Gram-Positive and Gram-negative Bacteria

Abstract

Several gram-positive bacilli and gram-negative bacteria were found to differ markedly in their ability to concentrate Mg2+ from simple chemically defined media. In cultures of the gram-negative bacteria the uptake of Mg2+ was quantitative over the range where growth was limited by the concentration of Mg2+. The gram-positive bacilli, however, were unable to utilize Mg2+ when the external concentration was low, and at higher concentrations sufficient to support about half maximal growth, assimilated less than 50% of the available Mg2+. Both gram-negative and gram-positive organisms initially liberated Mg2+ when suspended in Mg2+ free media, the Mg2+ being re-utilized rapidly by the gram-negative organisms. In suspensions of Aerobacter aerogenes the liberation of Mg2+ was independent of temperature and the re-utilization of Mg2+ was dependent on temperature.