Nitrogen-source dependent regulation of manganese oxidation in Pseudomonas sp. AN-1: Mechanistic insights from multi-omics analyses

Manganese-oxidizing bacteria (MnOB) mediate the oxidation of Mn(II) in both natural and engineered environments. Although numerous MnOB have been isolated, the regulatory mechanisms governing their Mn(II)-oxidizing activity in response to nitrogen sources remain poorly understood. This study investigates how nitrogen sources affect the Mn(II)-oxidizing capability of Pseudomonas sp. AN-1. Mn(II) oxidation was completely inhibited in NH 4 + -supplemented cultures, with no detectable BioMnOx production throughout a 10-day incubation period. In contrast, complete oxidation of 100 μM Mn(II) occurred within 27 h when either NO 3 − or NO 2 − as the nitrogen source. Intriguingly, Mn(II) oxidation exhibited a histidine concentration-dependent pattern: no oxidation was observed at 0.5–1.0 mM histidine, whereas complete oxidation occurred at 2.5 mM. Transcriptomics and proteomics revealed NO 3 − -fed cultures exhibited significantly higher expression of manganese oxidation genes, including mnxG and mcoA , compared to histidine-supplemented cultures. Further analysis identified the MnxS/MnxR as essential for initiating the transcription of mnxG and mcoA . Bioinformatic analysis revealed this regulatory system is widely distributed in the genus Pseudomonas and frequently co-occurs with mnxG and mcoA . This study provides insight into nitrogen-source dependent regulation of bacterial Mn(II) oxidation, uncovering concentration-dependent effects and identifying the MnxS/MnxR system as a key regulatory node that integrates nitrogen sensing with Mn(II) oxidation.