Magnetic resonance microscopy of iron transport in methanogenic granules
Magnetic resonance microscopy of iron transport in methanogenic granules
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DOI：
10.1016/j.jmr.2009.07.013
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发表时间：
2009-10-01
影响因子：
2.2
通讯作者：
Van As, Henk
中科院分区：
文献类型：
--
作者：
Bartacek, Jan;Vergeldt, Frank J.;Van As, Henk
厌氧生物膜与铁、钴或镍等重金属之间的相互作用在很大程度上是未知的。磁共振成像(MRI)是一种非侵入性的方法，可以在原位研究生物膜基质中的金属运输。本研究定量研究了与乙二胺四乙酸酯(EDTA)结合的铁(1.75 mm)对产甲烷颗粒(球形生物膜)的渗透作用。利用三维Turbo自旋回波(TSE)测量获得了109×109×218微米(3)的空间分辨率和11分钟的时间分辨率。纵向弛豫度，即弛豫速率(1/T(1))与顺磁性金属离子浓度的关系的斜率，被用来测量产甲烷颗粒中铁浓度的时间变化。铁-EDTA络合物([FeEDTA](2))需要300min才能渗透到直径3-4 mm的产甲烷颗粒中。扩散在各个方向上都一样快，有促进扩散的通道和阻扩散带等不规则性。尽管有这些不规则性，整个过程可以用Fick的球体扩散方程来模拟，因为没有观察到[FeEDTA](2)在颗粒基质中的固定(或反应势垒的存在)。[FeEDTA](2)的有效扩散系数(D(Ejf))为2.8×10(11)m(2)S(1)，约为[FeEDTA](2)在水中有效扩散系数的4%。Fickian模型不符合发生在颗粒核心(占颗粒总体积的3-5%)的过程，那里发生了高达25%的铁的过饱和(与主体溶液中的浓度相比)。(C)2009 Elsevier Inc.保留所有权利。
Interactions between anaerobic biofilms and heavy metals such as iron, cobalt or nickel are largely unknown. Magnetic resonance imaging (MRI) is a non-invasive method that allows in situ studies of metal transport within biofilm matrixes. The present study investigates quantitatively the penetration of iron (1.75 mM) bound to ethylenediaminetetraacetate (EDTA) into the methanogenic granules (spherical biofilm). A spatial resolution of 109 x 109 x 218 mu m(3) and a temporal resolution of 11 min are achieved with 3D Turbo Spin Echo (TSE) measurements. The longitudinal relaxivity, i.e. the slope the dependence of the relaxation rate (1/T(1)) on the concentration of paramagnetic metal ions, was used to measure temporal changes in iron concentration in the methanogenic granules. It took up to 300 min for the iron-EDTA complex ([FeEDTA](2)) to penetrate into the methanogenic granules (3-4 mm in diameter). The diffusion was equally fast in all directions with irregularities such as diffusion-facilitating channels and diffusion-resistant zones. Despite these irregularities, the overall process could be modeled using Fick's equations for diffusion in a sphere, because immobilization of [FeEDTA](2) in the granular matrix (or the presence of a reactive barrier) was not observed. The effective diffusion coefficient (D(ejf)) of [FeEDTA](2) was found to be 2.8 x 10 (11) m(2) s (1), i.e. approximately 4% of D(ejf) of [FeEDTA](2) in water. The Fickian model did not correspond to the processes taking place in the core of the granule (3-5% of the total volume of the granule), where up to 25% over-saturation by iron (compare to the concentration in the bulk solution) occurred. (C) 2009 Elsevier Inc. All rights reserved.