The Influence of Growth-limiting Substrate and Medium NaCl Concentration on the Synthesis of Magnesium-binding Sites in the Walls of Bacillus subtilis var. niger
SUMMARY: A comparative study has been made of the influence of growth environment on the properties of the walls of Bacillus subtilis var. niger organisms, particularly with respect to ability to bind magnesium ions. The medium NaCl concentration and the nature of the growth-limiting substrate, in chemostat cultures, both affected markedly the subsequent affinity and capacity of the bacterial walls for Mg2+ adsorption. These changes correlated with differences in the phosphate content of the walls, which in turn related largely to changes in wall teichoic acid content. Thus it seemed that whenever a constraint to the adsorption of Mg2+ was applied (either by growing the organisms in a Mg2+-limited environment, or in one containing high concentrations of a competing ion), walls were synthesized that had an increased teichoic acid content and an increased affinity for magnesium ions. These results support the thesis that anionic polymers in the walls of Bacillus organisms (i.e. teichoic acids and teichuronic acids) are involved in cation assimilation.