Phoenix V R, Holmes W M
Department of Geographical and Earth Sciences, Gregory Building, University of Glasgow, Glasgow G12 8QQ, United Kingdom.
Appl Environ Microbiol. 2008 Aug;74(15):4934-43. doi: 10.1128/AEM.02783-07. Epub 2008 Jun 13.
Magnetic resonance imaging (MRI) was used to spatially resolve structure, water diffusion, and copper transport and fate in a phototrophic biofilm [corrected]. MRI was able to resolve considerable structural heterogeneity, ranging from classical laminations approximately 500 mum thick to structures with no apparent ordering. Pulsed-field gradient (PFG) analysis spatially resolved water diffusion coefficients which exhibited relatively little or no attenuation (diffusion coefficients ranged from 1.7 x 10(-9) m(2) s(-1) to 2.2 x 10(-9) m(2) s(-1)). The biofilm was then reacted with a 10-mg liter(-1) Cu(2+) solution, and transverse relaxation time parameter maps [corrected].were used to spatially and temporally map copper immobilization within the biofilm. Significantly, a calibration protocol similar to that used in biomedical research successfully quantified copper concentrations throughout the biofilm. Variations in Cu concentrations were controlled by the biofilm structure. Copper immobilization was most rapid (approximately 5 mg Cu liter(-1) h(-1)) over the first 20 to 30 h and then much slower for the remaining 60 h of the experiment. The transport of metal within the biofilm is controlled by both diffusion and immobilization. This was explored using a Bartlett and Gardner model which examined both diffusion and adsorption through a hypothetical film exhibiting properties similar to those of the phototrophic biofilm. Higher adsorption constants (K) resulted in longer lag times until the onset of immobilization at depth but higher actual adsorption rates. MRI and reaction transport models are versatile tools which can significantly improve our understanding of heavy metal immobilization in naturally occurring biofilms.
磁共振成像（MRI）用于在光养生物膜中对结构、水扩散、铜传输及归宿进行空间分辨[已修正]。MRI能够分辨出相当大的结构异质性，范围从约500微米厚的经典分层到无明显有序排列的结构。脉冲场梯度（PFG）分析在空间上分辨了水扩散系数，其衰减相对较小或无衰减（扩散系数范围为1.7×10⁻⁹平方米每秒至2.2×10⁻⁹平方米每秒）。然后使生物膜与10毫克每升的Cu²⁺溶液反应，并使用横向弛豫时间参数图[已修正]在空间和时间上绘制生物膜内铜的固定情况。值得注意的是，一种类似于生物医学研究中使用的校准方案成功地对整个生物膜中的铜浓度进行了量化。铜浓度的变化受生物膜结构控制。在实验的前20至30小时内，铜的固定最为迅速（约5毫克铜每升每小时），然后在实验剩余的60小时内则慢得多。生物膜内金属的传输受扩散和固定两者控制。使用Bartlett和Gardner模型对此进行了探究，该模型通过一个具有与光养生物膜相似特性的假设膜来研究扩散和吸附。较高的吸附常数（K）导致在深度处开始固定之前的滞后时间更长，但实际吸附速率更高。MRI和反应传输模型是通用工具，可显著增进我们对天然生物膜中重金属固定的理解。
