Oxygen Generation via Water Splitting by a Novel Biogenic Metal Ion-Binding Compound

Area of Science:

• Biochemistry
• Microbiology
• Environmental Science

Background:

• Methanobactins (MBs) are copper-binding peptides essential for metal acquisition in methanotrophs.
• MBs can bind various metal ions, with some undergoing reduction, but the electron source remains unclear.

Purpose of the Study:

• To investigate the source of electrons for metal ion reduction by MBs.
• To determine if MBs can generate oxygen through water oxidation coupled to metal reduction.
• To assess if this oxygen can support methane oxidation under anoxic conditions.

Main Methods:

• Incubation of MBs with different metal ions (Au3+, Cu2+, Ag+, Fe3+, Hg2+, Ni2+, Co2+, K+, Mo2+) using H2 18O.
• Detection of 18,18O2 and protons released during metal ion reduction.
• Monitoring 13CH4 oxidation by Methylosinus trichosporium OB3b under anoxic conditions with MB-generated oxygen.

Main Results:

• MBs from Methylocystis sp. strain SB2 (MB-SB2) and Methylosinus trichosporium OB3b (MB-OB3) released 18,18O2 and protons when incubated with Au3+, Cu2+, or Ag+ in H2 18O.
• MB-SB2 reduced Fe3+, Hg2+, Ni2+, and Co2+ coupled to water oxidation and O2 generation.
• Oxygen generated by MB-OB3b supported methane oxidation by Methylosinus trichosporium OB3b under anoxic conditions.

Conclusions:

• MBs can oxidize water to generate O2 during metal ion reduction.
• This O2 self-generation mechanism allows methanotrophs to maintain activity in hypoxic/anoxic environments.
• MBs may play a crucial role in methane removal by enabling methanotrophs to colonize and function at oxic-anoxic interfaces.