Variation in content and distribution of magnesium, and its influence on survival, in Aerobacter aerogenes grown in a chemostat

SUMMARY: The magnesium and RNA contents of Aerobacter aerogenes, growth-limited by Mg2+, K+, NH4+ or carbon source, in defined media at 35° increased with growth rate. The results support the view that the amounts of these constituents are functions of the growth rate and are inter-dependent. Up to 26% of the total Mg2+ of bacteria freshly harvested from cultures containing excess magnesium was loosely bound to the bacterial surface; this adsorbed Mg2+ was removed by washing with 0·85% (w/v) NaCl but was unaffected by distilled water. Mg2+-limited bacteria had no surface-adsorbed magnesium. Surface-adsorbed Mg2+ stimulated polysaccharide synthesis, and affected the response of bacteria in saline buffer to stresses including starvation, heat-accelerated and substrate-accelerated death, and cold shock.