Collaborative Research: Interactions of Heavy Metals With Biofilm-Coated Mineral Surfaces

微生物生物膜是许多环境中矿物表面常见的涂层，众所周知，它可以吸附铅(II)等金属离子。然而，目前对这些金属离子在分子水平上的化学形态(S)、它们在生物膜中的空间分布以及生物膜影响金属离子在矿物表面吸附的机理还知之甚少。这个多学科项目将通过实验室研究铅(II)在铝和铁(氢)氧化物和石英的生物膜表面上的吸附作为几个溶液变量的函数来解决这些问题和相关问题。利用基于同步辐射的X射线和电子显微镜方法研究了生长在这些表面上的生物膜中铅(II)的分子尺度形态和空间分布。此外，我们还将利用红外光谱研究常见的无机配体PO43-以及细菌表面主要官能团的几种有机配体和生物膜外多糖对铅(II)吸收的影响。洋葱伯克霍尔德氏菌是一种好氧革兰氏阴性细菌，在营养有限的条件下很容易形成生物膜，它被选为这项工作的初始阶段。我们选择的系统变量将以我们正在进行的对法国北部莱德维尔的几个受铅污染的尾矿和土壤中铅形态的研究结果为指导。将探讨生物膜中胞外磷酸盐和胞内邻位和多聚磷酸盐代谢在生产磷酸铅中的作用。我们的方法从相对简化的模型系统开始，并系统地增加了自然系统的一些复杂性。这项工作的最终目标是对控制水环境中铅和其他金属的地球化学循环(以及潜在的生物有效性)的一些因素有一个基本的了解。这项建议是应环境地球化学和生物地球化学征集NSF 99-9的要求提交的，由化学部、地球科学部、海洋科学部和MPS多学科活动办公室联合资助。

Brown/Sporman9905755Microbial biofilms are common coatings on mineral surfaces in many environments and are known to sorb metal ions such as Pb(II). However, little is currently known about the chemical form(s) of these metal ions at a molecular level, their spatial distribution in the biofilm, and the mechanisms by which the biofilm affects metal ion sorption on mineral surfaces. This multidisciplinary project will address these and related issues through laboratory studies of Pb(II) sorption on biofilm-coated surfaces of aluminum and iron (hydr)oxides and quartz as a function of several solution variables. The molecular-scale speciation and spatial distribution of Pb(II) in biofilms grown on these surfaces will be studied using synchrotron-based x-ray and electron microscopy methods. In addition, we will use infrared spectroscopy to study the effects on Pb(II) uptake of the common inorganic ligand PO43- and several organic ligands that are dominant functional groups on bacterial surfaces and biofilm exopolysaccharides. Burkholderia cepacia, an aerobic gram-negative bacterium that readily forms biofilms under nutrient-limited conditions, was chosen for the initial phases of this work. Our choice of system variables will be guided by the results of our ongoing studies of Pb speciation in several Pb-contaminated tailings at Leadville, CO and soils in northern France. The role of extracellular phosphate and of intracellular ortho- and polyphosphate metabolism in the biofilm in producing Pb-phosphates will be explored. Our approach starts with relatively simplified model systems and systematically adds some of the complexities of natural systems. The ultimate goal of this work is to develop a fundamental understanding of some of the factors that control the geochemical cycling (and potential bioavailability) of Pb and other metals in aquatic environments.This proposal was submitted in response to the Environmental Geochemistry and Biogeochemistry solicitation NSF 99-9, and is being funded jointly by the Divisions of Chemistry, Earth Sciences, Ocean Sciences, and MPS Office of Multidisciplinary Activities.