Decoupling of Growth and Functional Activity in Manganese-Oxidizing Bacteria under High Temperature: A Constraint on Microbial Remediation of Soil Arsenic Contamination.

Manganese-oxidizing bacteria (MnOB) provide a biological approach for arsenic immobilization, but their performance under elevated temperatures remains unclear. This study isolated Pseudomonas sp. B10, closely related to P. putida GB-1, is capable of rapid arsenic immobilization through amorphous iron-manganese oxide (AIMO) formation. However, a decoupling between bacterial growth and Mn(II) oxidation was observed at 35 °C, with Mn(II) oxidation activity dropping over 90% despite unchanged biomass. Arsenic exposure did not affect bacterial Mn(II) oxidation, confirming temperature as the primary stressor. Transcriptomic analysis revealed up-regulation of Mn(II)-oxidation genes (mnxG, mcoA, mntP, mopA), suggesting post-transcriptional inhibition. Crude enzyme assays supported this, showing only 23.2% residual activity at 35 °C. Up-regulation of ethanol fermentation genes (e.g., adhE) may divert carbon from the TCA cycle, reducing NADH supply and exacerbating Mn(II)-oxidation loss. This study provides mechanistic insights into the temperature sensitivity of MnOB-mediated arsenic remediation and offers references for functional enhancement under high-temperature conditions.