Mechanisms of Low-Dose Nano Zerovalent-Iron-Induced Microbial Community Evolution: Extracellular Secretion and Key Transcriptional Response

Nano zerovalent-iron (nZVI) has shown considerable potential to improve conventional biological treatment processes. Designing low-dose exposure strategies is critical for biological nanosystems to avoid oxidative stress and subsequent inhibitory reactions. However, knowledge gaps remain in exploring adaptive evolutionary theories of low-dose exposure strategies, particularly in understanding the full complexity of transcriptional responses. In this study, systemic metrics and extracellular secretion behavior were analyzed holistically. A self-organizing mapping network algorithm was introduced to reveal key transcriptional patterns under low-dose nZVI exposure. Low-dose nZVI triggered extracellular secretion as the initial response, with uniform network structures in tightly bound extracellular polymers reflecting the core interaction variability. Moreover, the characteristic responses of the redox activity and energy exchange were found to underlie the transcriptional pattern of low-dose exposure. In contrast, the characteristic response pattern to high doses of nZVI suggested the activation of various repair and adaptation processes in the microbial community. These findings highlight a unique evolutionary mechanism for low-dose nZVI exposure and deepen our understanding of the selection of nZVI binding strategies by biological treatment processes.