Waterborne pathogens are a major health threat and must be eliminated to guarantee safe usage of water for potable purposes. For this purpose, a new carbon-based nanomaterial composed of single-walled carbon nanotubes (SWCNTs) and iron oxides was constructed for bacterial inactivation. Owing to its magnetic properties, the SWCNT–iron oxide nanocomposite may serve as a reusable antimicrobial agent. The nanocomposite material exhibited high antimicrobial activity against Escherichia coli. Successful reuse of the nanocomposite material was achieved by washing with calcium chloride and distilled water, which restored its performance for several successive cycles. To investigate the cytotoxicity mechanisms of the nanocomposite material, we exposed it to single-gene knockout mutant strains of E. coli. Mutants bearing shorter lipopolysaccharide (LPS) layers in the outer membrane (ΔrfaC and ΔrfaG) demonstrated an increased sensitivity in comparison to the wildtype strain, exemplified in enhanced removal by the nanocomposite material. This finding suggests that the LPS acts as a protective shield against the nanocomposite material. Inactivation of mutants impaired in specific oxidative stress defense mechanisms (ΔsodA, ΔkatG and ΔsoxS) emphasized that oxidative stress plays a significant role in the inactivation mechanism of the nanocomposite. This study sheds light on the mechanisms of bacterial inactivation by carbon-based nanomaterials and advances their potential implementation for water disinfection.

中文翻译：

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碳纳米管-氧化铁纳米复合材料的细菌失活：使用大肠杆菌突变体的机制研究†

水性病原体是主要的健康威胁，必须消除，以确保安全地将水用于饮用水。为此，构建了一种由单壁碳纳米管（SWCNT）和氧化铁组成的新型碳基纳米材料，用于细菌灭活。由于其磁性，SWCNT-氧化铁纳米复合材料可作为可重复使用的抗菌剂。该纳米复合材料对大肠杆菌表现出很高的抗菌活性。通过用氯化钙和蒸馏水洗涤，纳米复合材料获得了成功的再利用，从而在连续几个周期内恢复了其性能。为了研究纳米复合材料的细胞毒性机制，我们将其暴露于大肠杆菌的单基因敲除突变株中。。与野生型菌株相比，在外膜中带有较短脂多糖（LPS）层的突变体（ΔrfaC和ΔrfaG）表现出更高的敏感性，例如纳米复合材料的去除能力增强。该发现表明，LPS充当针对纳米复合材料的保护罩。在具体的氧化应激防御机制受损的突变体（Δ灭活苏打，Δ katG基因和Δ soxS）强调，氧化应激在纳米复合材料的灭活机制显著的作用。这项研究揭示了碳基纳米材料灭活细菌的机制，并提高了其在水消毒中的潜在应用。