Isolation, identification, and characterization of an Mn(Ⅱ) oxidizing bacterium Pseudomonas aeruginosa L3

Abstract:

[Background] Mn(Ⅱ)-oxidizing bacteria can precipitate and oxidize Mn(Ⅱ) to form solid manganese oxides, which have attracted much attention in the field of biogeochemistry and environmental remediation. However, most of the studied Mn(Ⅱ)-oxidizing model strains originated from the ocean, and fewer Mn(Ⅱ) oxidizing bacteria from soil sources were involved. [Objective]To enrich the available source of soil-derived Mn(Ⅱ) oxidizing bacteria, and also provide a new strain for the potential application of bixbyite-type Mn₂O₃.[Methods] In this study, Pseudomonas aeruginosa L3, was isolated from a ceased smelting industrial park at Zhuzhou, Hunan Province, and a systemic assay was conducted on its isolation and purification, identification, growth curves, pH alteration, Mn(Ⅱ) oxidation, and structure of manganese oxide. [Results] The cell suspension, the supernatant after centrifugation, and the pyocyanin extracted from the cell suspension all exhibited the ability to oxidize Mn(Ⅱ). In particular, the supernatant showed a stronger ability for Mn(Ⅱ) oxidation than the cell suspension. The X-ray diffraction (XRD) spectrum was further used to record the crystalline phase of manganese oxide produced by P. aeruginosa L3. The result showed that the manganese oxide had two characteristic peaks at 2θ=32.951° and 55.189°, indicating that its crystalline structure was the poorly-crystalline bixbyite-type Mn₂O₃.[Conclusion] P. aeruginosa L3 has a high Mn(Ⅱ) tolerance and oxidation ability, and the supernatant has a higher Mn(Ⅱ) oxidation ability than the cell suspension. Its Mn(Ⅱ) oxidation process may be associated with pyocyanin, and the Mn oxides are similar to poorly-crystalline bixbyite-type Mn₂O₃.