"Contamination with organic pollutants is widespread in nature and a notorious threat to our water resources. Two central paradigms are currently understood to control biodegradation in groundwater and sediments: (i) Redox gradients and interphases between compartments are hot-spots for contaminant breakdown, and (ii) biodegradation is primarily limited by local electron acceptor availability, in particular of oxygen. My group has published leading contributions to this understanding in recent years, especially in elucidating the ecology of anaerobic toluene degraders in aquifers.This project now aims to question these established paradigms and to elaborate a ground-breaking new perspective of the role of molecular oxygen in pollutant degradation in anoxic compartments. The hypotheses at the heart of the project originate from a combination of own recent findings, partially inconsistent with the current understanding of process and degrader stratification at redox gradients. These are now interpreted in the light of exciting recent advances in the fields of electromicrobiology and oxygenic anaerobic respiration.POLLOX postulates that oxygen-dependent degradation of pollutants in anaerobic compartments is possible by two unrecognised physiological adaptations of degraders. I want to verify the hypothesis that filamentous Desulfobulbaceae can anaerobically oxidise toluene via long-distance (1-2 cm) electron transfer to oxygen across redox gradients (aim 1). Furthermore, I postulate that monooxygenase-dependent toluene degraders, in absence of external oxygen, can be active via self-sustained production of oxygen by nitric oxide dismutation (aim 2). POLLOX proposes to perform targeted lab experiments and field surveys to verify both hypotheses and to elaborate the ecological niches in which respective degraders and processes are relevant in situ (aim 3). The generic mechanisms to be elaborated here have the potential to open new doors for bioremediation in the future."