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Pseudomonas putida coordinates the expression of two manganese oxidases and optimizes manganese oxide precipitation in response to aqueous Mn(II)

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Feb 04, 2026 version files 978.09 MB

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Abstract

Manganese (Mn) oxides are commonly precipitated by bacteria and fungi. Recent studies have shown that Mn-oxidizing bacteria can harbor multiple Mn oxidases, but the environmental controls on the regulation of these enzymes are unknown. Here, we examine the dynamic activation of the genes encoding for MnxG and McoA, two Mn oxidases in Pseudomonas putida GB-1 in response to varying Mn(II) concentrations. Using reporter gene fusion strains, we found that mnxG and mcoA are activated in an increasingly larger proportion of the population with increasing initial Mn(II) concentrations. The two genes showed specificity to the Mn(II) concentration range, with an increasing fraction of the population activating mnxG from 0 to 10 µM Mn(II) and from 10 to 500 µM for mcoA. Kinetic modeling showed that co-expression of mnxG and mcoA alleviates substrate saturation and inhibition of MnxG at high Mn(II) concentrations, while allowing for an eight-fold increase in the initial rate of Mn oxidation in the wild-type compared to strains lacking mnxG or mcoA. The population-level control of gene activation and, ultimately, Mn oxide precipitation in response to the initial Mn(II) concentration shows that P. putida fine-tunes the regulation of its Mn oxidases to operate under varying environmental conditions.