Evidence for a magnesium pump in Bacillus cereus T

Area of Science:

• Microbiology
• Molecular Biology
• Biochemistry

Background:

• Magnesium (Mg2+) is essential for bacterial growth and cellular processes.
• Different bacterial species exhibit varying mechanisms for Mg2+ uptake and regulation.
• Understanding Mg2+ homeostasis is crucial for comprehending bacterial physiology.

Purpose of the Study:

• To investigate the Mg2+ accumulation and homeostasis in Bacillus cereus T.
• To compare the Mg2+ regulation mechanisms between Bacillus cereus T and Escherichia coli.
• To explore the relationship between external Mg2+ concentration and intracellular Mg2+ levels in B. cereus T.

Main Methods:

• Culturing Bacillus cereus T and Escherichia coli under varying Mg2+ concentrations.
• Measuring intracellular Mg2+ concentrations in the cell sap.
• Assessing ribosome-bound Mg2+ and spermidine levels.
• Evaluating the effect of Mg2+ on streptomycin-induced growth inhibition.

Main Results:

• Bacillus cereus T maintains a constant intracellular Mg2+ concentration (approx. 6 x 10(-3)m) despite external fluctuations.
• Ribosome-bound Mg2+ and spermidine concentrations remain stable in B. cereus T across different Mg2+ levels.
• Increased Mg2+ reversed streptomycin inhibition in E. coli but not in B. cereus T.

Conclusions:

• Bacillus cereus T actively accumulates Mg2+ against a concentration gradient, establishing a stable intracellular environment.
• This Mg2+ homeostasis mechanism in B. cereus T differs significantly from that of E. coli.
• The findings suggest a unique Mg2+ regulatory system in B. cereus T, contributing to its physiological characteristics.