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Manganese oxidation by an intracellular protein of a Pseudomonas species
Abstract:
Cultures of a Pseudomonas sp. strain MnB 1 produce an intracellular, manganese oxidizing protein (abbrev. as Mn ox. protein) during the stationary phase of growth. This protein is heat labile, can be inactivated by protease and has a pH-optimum for manganese oxidation at pH 7.0. Mn2+ is oxidized only at concentrations below 3-10(-5) M. The occurrence of the protein is not dependent on the presence of Mn2+, but is clearly related to the cessation of growth after the end of the exponential growth phase. Oxygen, coenzymes, and low molecular weight components of the cell extract seem not to be involved in the reaction as electron acceptors for the oxidation of Mn2+. Continued manganese oxidation by Mn ox. protein results in a progressive decrease in activity which corresponds to the amount of formed manganese oxide.
Insights
A Pseudomonas sp. strain produces an intracellular manganese oxidizing protein during stationary growth. This heat-labile protein facilitates manganese oxidation at pH 7.0, with activity decreasing as manganese oxide forms.
Area of Science:
- Microbiology
- Biochemistry
- Environmental Science
Background:
- Pseudomonas species are known for diverse metabolic capabilities.
- Manganese oxidation plays a role in biogeochemical cycles.
- Understanding microbial enzymes involved in metal transformation is crucial.
Purpose of the Study:
- To characterize a novel intracellular manganese oxidizing protein from Pseudomonas sp. strain MnB 1.
- To investigate the properties and optimal conditions for manganese oxidation by this enzyme.
- To explore the relationship between protein activity and manganese oxide formation.
Main Methods:
- Culturing of Pseudomonas sp. strain MnB 1.
- Isolation and partial purification of the intracellular manganese oxidizing protein.
- Enzymatic assays to determine optimal pH, substrate concentration, and heat/protease sensitivity.
- Monitoring of manganese oxidation and manganese oxide formation.
Main Results:
- An intracellular manganese oxidizing protein (Mn ox. protein) was identified in Pseudomonas sp. strain MnB 1 during stationary phase.
- The Mn ox. protein is heat labile and inactivated by protease, with optimal activity at pH 7.0.
- Manganese (Mn2+) oxidation occurred at low concentrations (< 3 x 10(-5) M) and was independent of Mn2+ presence during protein production.
- Enzyme activity decreased with increasing manganese oxide formation, suggesting product inhibition or enzyme denaturation.
Conclusions:
- Pseudomonas sp. strain MnB 1 possesses an intracellular enzyme responsible for manganese oxidation.
- The enzyme's characteristics suggest a specific role in manganese transformation during the stationary growth phase.
- The study provides insights into microbial mechanisms of manganese cycling and potential applications in bioremediation or biomining.