The Influence of Certain Trace Metals on Bacterial Growth and Magnesium Utilization

Abstract

The uptake of Mg2+ in Mg2+-limited cultures of the gram-negative Escherichia coli is rapid and is complete some time before the onset of the stationary phase. In similar cultures of the gram-positive Bacillus megaterium and B. subtilis F3 growth and Mg2+ assimilation cease at the same time and when only part of the available Mg2+ was utilized; thereafter efflux of the cation may occur. In these cultures as in dilute suspensions of the bacilli in a Mg2+-deficient medium, viability is maintained in a high percentage of the organisms; and growth occurs on the addition of Mg2+ even if this is delayed for 20 hr. The minimum growth-requirement for Mg2+ varies for different gram-positive bacilli and is particularly low for B. subtilis var. niger. The response of this organism to Mg2+ is unaffected by Mn2+2 The Mg2+ requirements of B. megaterium and B. subtilis F3, are reduced by 25 [mu]m Mn2+. Although this con-centration of Mn2+ is unable to support growth in the complete absence of Mg2+, it appears to stimulate the uptake of the latter cation from dilute solutions. The Mn2+ also assimilated during growth by both gram-positive and gram-negative bacteria (although less efficiently than Mg2+) and is incorporated into the ribosomes.