Dissolved DNA (D‐DNA) is a ubiquitous component of dissolved organic matter in aquatic systems. It is operationally defined as the DNA that passes a membrane filter and thus includes pools of truly dissolved “free” DNA (F‐DNA), virion encapsidated DNA, DNA within membrane vesicles, and possibly other bound forms, each with different sources and lability. We investigated whether filtration (< 0.1 μm), concentration by tangential flow ultrafiltration (> 30 kDa), and fractionation in an equilibrium buoyant density gradient could be used to discriminate the mass contributions of the different pools of filterable DNA in seawater. Spike‐in experiments with a known range of DNA standards (75–20,000 bp) indicated that this method results in high recoveries of F‐DNA (68–86%) with minimal degradation. Application of the fractionation method to seawater samples collected from the oligotrophic North Pacific Ocean followed by analysis of fractions (epifluorescence and electron microscopy, DNase digestion) suggested that the low‐density fractions (1.30–1.35 g mL⁻¹) were dominated by vesicle‐like particles, mid‐density fractions (1.45–1.55 g mL⁻¹) by virus‐like particles, and high‐density fractions (1.60–1.70 g mL⁻¹) by F‐DNA. The estimated concentration of DNA that is either F‐DNA, in viruses, or in vesicles was 0.13, 0.14, and 0.08 μg L⁻¹, respectively in the euphotic zone and 0.09, 0.04, and 0.03 μg L⁻¹, respectively in the mesopelagic zone. The approach described should be useful for more detailed investigations of the abundance, dynamics, and sources of DNA in the distinct pools that comprise filterable DNA in aquatic environments.

中文翻译：

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表征溶解DNA的方法及其在北太平洋亚热带环流中的应用

溶解的DNA（D-DNA）是水生系统中溶解有机物的普遍成分。它在操作上被定义为通过膜滤器的DNA，因此包括真正溶解的“游离” DNA（F-DNA），病毒体衣壳化的DNA，膜囊泡中的DNA以及可能的其他结合形式，每个都有不同的来源和不稳定性。 。我们调查了过滤（< 0.1μm），通过切向流超滤（> 30 kDa）进行浓缩以及在平衡浮力密度梯度中进行分馏可用于区分海水中不同可过滤DNA池的质量贡献。使用已知范围的DNA标准品（75–20,000 bp）进行的尖峰实验表明，此方法可实现F‐DNA的高回收率（68–86％），且降解程度最小。将分馏方法应用于从贫营养性北太平洋收集的海水样品，然后进行馏分分析（荧光和电子显微镜，DNase消化）表明，低密度馏分（1.30–1.35 g mL ^-1）以囊泡为主。像颗粒一样，中等密度分数（1.45-1.55 g mL ^-1病毒样颗粒）和F-DNA的高密度级分（1.60–1.70 g mL ^-1）。DNA的估计浓度要么是F-DNA，在病毒中，或在囊泡为0.13，0.14，和0.08  μ克L- ^-1，分别在透光层和0.09，0.04，和0.03  μ克L- ^-1，分别在近视区。所描述的方法对于更详细地研究水生环境中包含可过滤DNA的不同池中DNA的丰度，动态和来源应该是有用的。