Spatial distributions of copper in microbial biofilms by scanning electrochemical microscopy
Spatial distributions of copper in microbial biofilms by scanning electrochemical microscopy
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DOI：
10.1021/es061293k
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发表时间：
2007-02-01
影响因子：
11.4
通讯作者：
Lion, Leonard W.
中科院分区：
文献类型：
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作者：
Hu, Zhiqiang;Jin, Jing;Lion, Leonard W.
利用扫描电化学显微镜（SECM）测定了大肠杆菌PHL 628生物膜中Cu的空间分布，该显微镜由微电极和压电微定位系统组成。在-0.7V（vsAg/AgCl）下，Cu在微电极上还原沉积4 min后，用伏安溶出法测定了水溶液中不稳定的铜物种。本体溶液-生物膜界面的位置由作为氧化还原指示剂加入的0.4 mM羟甲基二茂铁产生的电流变化确定。暴露于0.2 mM铜2小时后，Cu位于生物膜的上部区域，渗透深度小于150 μ m。一维扩散传输模型充分描述了铜在生物膜中的空间分布，但铜在生物膜中的阻滞因子比从铜结合到E. coliPHL 628细胞。这种差异有几个可能的原因，包括生物膜内每个细胞的细胞外聚合物的量增加和/或可能阻碍Cu转运到生物膜中的弯曲度。SECM技术与模型计算相结合提供了直接证据，支持生物膜的形成可以通过延缓金属扩散和减少生物膜内细胞的金属暴露来赋予对有毒金属物质的本体溶液浓度中的瞬时峰值的抗性的概念。
The spatial distribution of Cu was determined in Escherichia coli PHL628 biofilms using a scanning electrochemical microscope (SECM) consisting of a microelectrode in conjunction with a piezoelectric micropositioning system. Aqueous labile copper species were determined using voltametric stripping after reductive deposition of Cu for 4 min on the microelectrode at -0.7 V (vs Ag/AgCl). The position of the bulk solution-biofilm interface was determined from the change in current produced by 0.4 mM hydroxymethyl ferrocene that was added as a redox indicator. After a 2 h exposure to 0.2 mM copper, Cu was located in the upper region of the biofilm with a penetration depth less than 150 mu m. A one-dimensional diffusive transport model adequately described the spatial distribution of copper in the biofilm, but the Cu retardation factor in the biofilm was more than 6-fold larger than that calculated from the isotherm for Cu binding to suspensions of E. coli PHL628 cells. There are several possible reasons for this difference, including an increase in the amount of extracellular polymer per cell within the biofilm and/or tortuosity that might hinder Cu transport into biofilms. The SECM technique in combination with model calculations provides direct evidence in support of the concept that formation of a biofilm may confer resistance to transient spikes in the bulk solution concentration of toxic metal species by retarding metal diffusion and reducing the metal exposure of cells within the biofilm.