Analysis of manganese oxidase and its encoding gene in Lysinibacillus strain MK-1

Manganese (Mn) is one of the most abundant transitional metals in the crust of the Earth and Mn contamination is occurring in groundwater worldwidely. The removal of manganese is mainly achieved by catalytic oxidation of manganese-oxidizing bacteria. As a result, biological Mn-removal technology has attracted increased attention due to its high efficiency and convenience. Several species of bacteria, including Bacillus and Pseudomonas, have the ability to oxidize Mn. A bacterial strain MK-1 from Lysinibacillus, capable of oxidizing 98% of Mn under optimal conditions (1mmol/L of Mn(II), pH 7.0, 3days), was obtained from a mine located in Hunan province, and a gene, mokA, putatively encoding a manganese oxidase, was identified. The MokA enzyme produced by mokA is a CotA-like multicopper oxidase (MCO) that exhibited significantly different expression profiles in medium with and without Mn(II). Sequence analysis of MokA revealed that it is structurally similar to previously reported manganese oxidases. The results of this study broaden the taxonomic range manganese-oxidizing bacteria. Based on these results, our findings suggested that MK-1 might be applied for the treatment of Mn(II)-contaminated water.