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的常见涂层，已知可以吸附金属离子，如Pb（II）。然而，目前对这些金属离子在分子水平上的化学形态、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制知之甚少。这个多学科项目将通过实验室研究铅（II）吸附在铝和铁（氢）氧化物和石英的生物膜表面作为几个溶液变量的函数来解决这些问题和相关问题。在这些表面生长的生物膜中，Pb（II）的分子尺度形态和空间分布将通过基于同步加速器的x射线和电子显微镜方法进行研究。此外，我们将利用红外光谱研究常见无机配体PO43-和几种有机配体对Pb（II）吸收的影响，这些配体是细菌表面和生物膜外多糖的优势官能团。洋葱伯克霍尔德菌是一种需氧革兰氏阴性菌，在营养有限的条件下容易形成生物膜，被选为这项工作的初始阶段。我们对系统变量的选择将以我们正在进行的在Leadville、CO和法国北部土壤中几种铅污染的尾矿中Pb形态的研究结果为指导。将探讨生物膜中细胞外磷酸盐和细胞内正磷酸盐和多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，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水生环境中控制铅和其他金属的地球化学循环（和潜在的生物利用度）的一些因素有一个基本的了解。该提案是响应环境地球化学和生物地球化学招标NSF 99-9而提交的，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。

Traina9910569Microbial 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.