title: Sequestration of nanoparticles by an EPS matrix reduces the particle-specific bactericidal activity.
abstract: Most artificial nanomaterials are known to exhibit broad-spectrum bactericidal activity; however, the defence mechanisms that bacteria use based on extracellular polymeric substances (EPS) to detoxify nanoparticles (NPs) are not well known. We ruled out the possibility of ion-specific bactericidal activity by showing the lack of equivalent dissolved zinc and silicon toxicity and determined the particle-specific toxicity of ZnO and SiO2 nanoparticles (ZnONPs/SiO2NPs) through dialysis isolation experiments. Surprisingly, the manipulation of the E. coli EPS (i.e., no EPS manipulation or EPS removal by sonication/centrifugation) showed that their particle-specific bactericidal activity could be antagonized by NP-EPS sequestration. The survival rates of pristine E. coli (no EPS manipulation) reached 65% (ZnONPs, 500 mg L(-1)) and 79% (SiO2NPs, 500 mg L(-1)), whereas survival rates following EPS removal by sonication/centrifugation were 11% and 63%, respectively. Transmission electron microscopy (TEM) combined with fluorescence micro-titration analysis and Fourier-transform infrared spectroscopy (FTIR) showed that protein-like substances (N-H and C-N in amide II) and secondary carbonyl groups (C=O) in the carboxylic acids of EPS acted as important binding sites that were involved in NP sequestration. Accordingly, the amount and composition of EPS produced by bacteria have important implications for the bactericidal efficacy and potential environmental effects of NPs.
authors: State Key Laboratory of Lake Science and Environment, Nanjing Institute of Geography and Limnology, Chinese Academy of Sciences, Jiangsu 210008, China.|School of Earth Sciences and Engineering, Nanjing University, Jiangsu 210046, China.
authors: Qian
authors: Q
authors: Wang
authors: Institute of Organic Contaminant Control and Soil Remediation/College of Resources and Environmental Sciences, Nanjing Agricultural University, Jiangsu 210095, China.
authors: Fuxing
authors: F
authors: Kang
authors: Institute of Organic Contaminant Control and Soil Remediation/College of Resources and Environmental Sciences, Nanjing Agricultural University, Jiangsu 210095, China.
authors: Yanzheng
authors: Y
authors: Gao
authors: Institute of Organic Contaminant Control and Soil Remediation/College of Resources and Environmental Sciences, Nanjing Agricultural University, Jiangsu 210095, China.
authors: Xuewei
authors: X
authors: Mao
authors: Institute of Organic Contaminant Control and Soil Remediation/College of Resources and Environmental Sciences, Nanjing Agricultural University, Jiangsu 210095, China.
authors: Xiaojie
authors: X
authors: Hu
mesh_terms: D000900:Anti-Bacterial Agents / Q000737:chemistry / Q000494:pharmacology; D004926:Escherichia coli / Q000254:growth & development*; D005109:Extracellular Matrix / Q000737:chemistry*; D053758:Nanoparticles / Q000737:chemistry*; D012822:Silicon Dioxide / Q000737:chemistry / Q000494:pharmacology; D015034:Zinc Oxide / Q000737:chemistry / Q000494:pharmacology
chemical_list: D000900:Anti-Bacterial Agents; D012822:Silicon Dioxide; D015034:Zinc Oxide