The effects and mechanisms of carbon (C)- and nitrogen (N)-deficient nutrient conditions (prevalent in natural environment) on bacterial mobile performance in porous media are unclear. This study systematically investigated the transport/retention performance of Gram-negative Escherichia coli and Gram-positive Bacillus subtilis experiencing different nutrient conditions (i.e. nutrient-sufficient, C-deficient, or N-deficient conditions) in column, parallel plate flow chamber (PPFC) and microfluidic chamber systems. We found that compared to those in nutrient-sufficient condition, bacteria (regardless of their type) exposure to C-deficient nutrient condition exhibited 7–14% reduced mobility in porous media, whereas those experienced N-deficient condition had 7–20% enhanced transport in both simulated electrolyte solutions and real groundwater samples. The underlying mechanisms driving to different mobile performance of bacteria exposure to different nutrient conditions were correlated with the composition of proteins (one major component of extracellular polymeric substances (EPS)). Compared to nutrient-sufficient condition, C-deficient condition increased EPS hydrophobicity via enhancing hydrophobic amino acids contents and altering secondary structure within proteins thus decreased bacterial transport, while N-deficient condition decreased EPS hydrophobicity through decreasing the abundance of hydrophobic amino acids within proteins and increased cell mobility. The results showed that via changing cell surface hydrophobicity, exposure bacteria to different nutrient conditions could induce different mobile performance of bacteria.

Antibiotic-resistant bacteria (ARB) and antibiotic-resistant genes (ARGs) pose global threats to human health and ecological safety. Activation of percarbonate (PC) by eco-friendly bismuth oxyiodide (BiOI) is a promising ARB/ARGs removal technique, yet its efficiency is hindered by the insufficient exposure of reactive Bi sites. Herein, we provide a facile protocol to fabricate BiOI with remarkable PC activation efficiency (BOI-C) for the ultrafast ARB/ARGs removal via modulating reactive Bi sites through introducing optimal Bi3-oxygen vacancy (OV) sites on the unsaturated facets. We show that BOI-C with optimal amount of Bi3-OV site can efficiently activate 50 µM PC to rapidly disinfect 7-log ARB to the limit of detection within only 4 min. Moreover, this reaction system can effectively degrade the released ARG and suppress the horizontal gene transfer process, greatly decreasing the risks of ARG dissemination. Negligible toxic halogen-containing disinfection byproducts is generated during the disinfection process, indicating the outstanding ecological safety of BOI-C/PC system. The reaction system can also effectively disinfect ARB under complex water chemistries including a broad pH range (3–9), high ionic strengths (up to 150 mM), copresence of natural organic matter (up to 10 mg L−1), and diverse actual water samples including tap water, lake water, groundwater and aquaculture tailwater. Furthermore, it can also be assembled into a filtration system for successive ARB disinfection, demonstrating the feasibility for practical application. The catalytic system also exhibits excellent ARB disinfection performance across various bacterial strains and effective degradation performance towards different types of emerging organic pollutants, suggesting its universal decontamination capability. Combining in-situ characterizations and theoretical calculations, we reveal that Bi3-OV sites on the unsaturated facets of BOI-C facilitate the p-p interaction with peroxy O atoms of PC molecules and trigger the electron transfer as well as the subsequent cleavage of peroxy bonds, generating abundant CO3•− for the ultrafast ARB disinfection. The results of this study show that BOI-C/PC system can be employed to effectively remove antibiotic resistance in real water.