The effects of manganese (II) but not nickel (II) ions on Enterococcus hirae cell growth, redox potential decrease,...

Area of Science:

• Microbiology
• Environmental Science
• Biochemistry

Background:

• Enterococcus hirae ferments glucose anaerobically, decreasing oxidation-reduction potential (Eh).
• Heavy metals like copper and iron influence E. hirae growth, Eh, and ion fluxes across the cell membrane.
• Understanding metal ion effects on bacterial physiology is crucial for microbial ecology and biotechnology.

Purpose of the Study:

• To investigate the impact of manganese (II) ions on E. hirae growth and Eh.
• To compare the effects of manganese (II) with nickel (II) ions.
• To elucidate the influence of these metal ions on proton-potassium (H(+)-K(+)) ion fluxes through the cell membrane.

Main Methods:

• Culturing E. hirae ATCC9790 in the presence of varying concentrations of manganese (II) and nickel (II) ions (0.01-1 mM).
• Monitoring bacterial growth parameters (lag phase duration, specific growth rate) and Eh.
• Assessing proton-potassium ion fluxes with and without the FoF1 ATPase inhibitor N,N'-dicyclohexylcarbodiimide (DCCD).

Main Results:

• Manganese (II) ions significantly decreased the lag phase duration and increased the specific growth rate of E. hirae.
• The decrease in Eh during E. hirae growth was shifted in the presence of manganese (II) ions.
• Nickel (II) ions did not induce visible changes in bacterial growth or Eh.
• Manganese (II) ions exhibited a stronger effect on H(+)-K(+) exchange in the presence of DCCD, suggesting interaction with membrane transport proteins.

Conclusions:

• Manganese (II) ions positively modulate E. hirae growth kinetics and Eh dynamics under anaerobic conditions.
• The observed effects of manganese (II) are likely mediated through alterations in proton-potassium ion transport across the cell membrane.
• Nickel (II) ions appear to have a negligible impact on E. hirae growth and Eh under the tested conditions.