Non-photosynthetic microorganisms drive the transformation of bioinert emerging contaminants through photoinduced singlet oxygen production.

Ubiquitous non-photosynthetic microorganisms play a crucial role in the environmental attenuation of contaminants. However, this microbial-driven transformation is often ineffective for bio-inert or bio-toxic emerging contaminants (ECs). Herein, we demonstrated that non-photosynthetic microorganisms such as Escherichia coli, Bacillus subtilis, Shewanella oneidensis and microorganisms from actual waters could produce singlet oxygen (1O2) through photoexcited extracellular metabolites, effectively driving the transformation of ECs such as cimetidine, estriol, and sulfamethoxazole. The extracellular metabolites of these non-photosynthetic microorganisms exhibited high photochemical 1O2-producing capability. The quantum yields of 1O2 produced by the extracellular metabolites of Escherichia coli, Bacillus subtilis, and Shewanella oneidensis were 25.02 ± 0.95%, 32.65 ± 1.53%, and 16.98 ± 0.37%, respectively, which were comparable to those of photosynthetic microorganisms, and notably higher than that of natural organic matter. For non-photosynthetic microorganisms, low-molecular-weight compounds (<1 kDa) in extracellular metabolites were primarily responsible for 1O2 photoproduction. Metabolomics revealed that diverse photosensitizers capable of producing 1O2, such as quinones, aromatic ketones, aromatic aldehydes, quinolines, indoles, aromatic amino acids and derivatives, were present in the extracellular metabolites. This work uncovered an overlooked transformation pathway of emerging contaminants by non-photosynthetic microorganisms, favoring a more accurate evaluation of their fate in environments.