Kim Kyungho, Sen Anindito, Chellam Shankararaman
Department of Civil & Environmental Engineering, Texas A&M University, College Station, Texas 77843-3136, United States.
Microscopy and Imaging Center, Texas A&M University, College Station, Texas 77843-2257, United States.
Environ Sci Technol. 2025 Aug 12;59(31):16697-16708. doi: 10.1021/acs.est.5c02792. Epub 2025 Jul 30.
Both FeCl conventional coagulation and Fe(0) electrocoagulation were highly effective in mitigating the long-tailed somatic phage P1. We targeted enterobacterial coliphages because they are better than fecal indicator bacteria in tracking environmental persistence of viral pathogens and their fate in wastewater unit operations. Cryogenic electron microscopy (cryo-EM) of intact/damaged P1 and enumeration of infective virions by plaque assays demonstrated control via both removal and inactivation. Cryo-single particle analysis was coupled with cryo-electron tomography to generate 3-dimensional electron density maps to visualize and analyze untreated and coagulated capsids. To our knowledge, this is the first report of cryo-EM to visualize structurally damaged viruses with environmental relevance. Viruses were intrinsically enmeshed in precipitates consistent with sweep coagulation. Direct evidence of multiple inactivation mechanisms was obtained including (i) capsid breakage leading to leakage of viral genome and other components, (ii) deformation and thinning of capsid proteins, (iii) severance/damages to the neck region where the tail is attached to the capsid, (iv) removal, fragmentation, and splintering of tail sections, and (v) baseplate damage (including receptor-binding proteins). Conformational alterations to proteins, changes to secondary structures, and specific interactions with flocs were inferred from infrared spectroscopy for both coagulation approaches. However, only electrocoagulation oxidized proteins. Extremely facile reduction of P1 suggested that coliphages with myovirus morphology may not be conservative surrogates to measure log reduction values for regulatory purposes and public health protection by iron conventional coagulation and electrocoagulation.
氯化铁传统混凝法和零价铁电凝法在减轻长尾体噬菌体P1方面都非常有效。我们将肠道杆菌噬菌体作为目标，因为它们在追踪病毒病原体在环境中的持久性及其在废水处理单元操作中的命运方面比粪便指示细菌更具优势。通过对完整/受损的P1进行低温电子显微镜（cryo-EM）观察以及通过噬菌斑测定法对感染性病毒粒子进行计数，结果表明这两种方法都是通过去除和灭活来实现控制的。低温单颗粒分析与低温电子断层扫描相结合，生成三维电子密度图，以可视化和分析未处理和混凝后的衣壳。据我们所知，这是首次利用低温电子显微镜对具有环境相关性的结构受损病毒进行可视化的报告。病毒本质上被包裹在与扫集混凝一致的沉淀物中。获得了多种灭活机制的直接证据，包括：（i）衣壳破裂导致病毒基因组和其他成分泄漏；（ii）衣壳蛋白变形和变薄；（iii）尾部与衣壳连接的颈部区域断裂/受损；（iv）尾部片段的去除、破碎和分裂；（v）基板损伤（包括受体结合蛋白）。通过红外光谱法推断了两种混凝方法中蛋白质的构象改变、二级结构变化以及与絮体的特定相互作用。然而，只有电凝法能氧化蛋白质。P1极易被还原，这表明具有肌尾病毒形态的噬菌体可能不是用于通过铁传统混凝法和电凝法测量对数去除值以进行监管目的和公共卫生保护的保守替代物。
