Environmental stress sensitivity determines bacterial Mn(II) oxidation

Bacterial Mn(II) oxidation is a widespread and ecologically significant process, with Mn oxides playing essential roles in biogeochemical cycling and environmental remediation. However, the environmental cues that initiate this microbial activity remain enigmatic. In this study, a spontaneous mutant was isolated from the previously characterized Arthrobacter strain that exhibited autonomous Mn(II)-oxidizing capacity, in contrast to the parental strain, which required cocultivation with other bacteria to initiate Mn(II) oxidation1. Comparative transcriptomic analysis suggested that a gene system encoding an environmental stress-sensing receptor controlled the transcription of boxA, a Mn(II)-oxidizing gene. These findings indicate that two conditions are required for bacterial Mn(II) oxidation: the presence of a Mn(II)-oxidizing gene and an environmentally responsive regulatory system capable of activating its expression. Based on this knowledge, eight additional bacterial strains were isolated that triggered Arthrobacter Mn(II) oxidation. Transcriptomic profiling revealed a robust positive correlation between boxA expression and genes encoding two-component signal transduction systems. Given their widespread distribution (approximately 23% of environmental bacterial genomes harbor Mn(II)-oxidizing gene homologs2) and constant exposure to diverse biotic and abiotic stressors, these bacteria are likely to undergo frequent Mn(II) oxidation triggered by microbial interactions or chemical signals. This study provides critical mechanistic insight into the environmental regulation of bacterial Mn(II) oxidation, addressing a longstanding gap in understanding its natural occurrence.