Microbial reduction of metalloid oxyanions: significance of geochemical factors

背景和理由真菌和细菌是陆地生境中的主要地质活性物质，可以通过还原转化Se和Te氧离子，从而降低流动性和毒性(Gadd2010；Glasauer等人)。2013)。Se/Te还原似乎是一种广泛发现的特性，并有可能将大量这些类金属固定为元素Se或Te(Gadd1993；Gharieb等人)。1995)，它可以以纳米颗粒、晶状和棒状沉积在细胞内或细胞外(Hockin和Gadd2003,2006；Oem land等人)。2004年；Baesman等人。2007)。然而，几乎所有的详细研究都是用厌氧性的硒呼吸细菌或硫酸盐还原细菌进行的(Hockin和Gadd，2003,2006)。令人惊讶的是，关于好氧生物中Se或Te还原的信息很少，尽管这种能力似乎无处不在(Gharieb等人。1995年)。此外，对有氧生境中类金属还原的地球化学影响和限制，几乎一无所知。在土壤或沉积物中存在多种矿物相、其他氧化还原敏感金属(Loid)S(如Fe、As)、不同营养水平和有机含量以及其他生物的复杂环境中，类金属还原如何进行？工作计划本项目的目的是使用简单到中等复杂性的模型系统，检查好氧微生物还原Se/Te的地球化学影响，以确定和了解该过程存在哪些限制，以及它们的重要性。将描述其他金属和矿物成分、有机成分和营养物质对地活性细菌和真菌菌株类金属还原能力的影响，以及菌株影响其他金属-矿物转化的能力。将使用简单的纯培养系统以及混合的细菌-真菌微观世界和模拟土壤基质。还将调查非生物对沉淀类金属的形式和位置的影响。因此，该项目将提供有关好氧Se/Te还原及其意义的基本科学信息，从而增加我们目前对Se/Te生物地球化学的理解。这个项目将使用跨学科的方法，学生将接受地球微生物学和环境矿物学方面的培训，以及相关的分析和准备技术，包括实验生物体的生长和操作，以及原子吸收光谱(AAS)、X射线粉末衍射(XRPD)、高级光学和电子显微镜、X射线元素分析和绘图等技术。

Background and rationaleFungi and bacteria are the major geoactive agents in terrestrial habitats and can transform Se and Te oxyanions by reduction, which reduces mobility and toxicity (Gadd, 2010; Glasauer et al. 2013). Se/Te reduction appears to be a widely found property, and has the potential to immobilize substantial amounts of these metalloids as elemental Se or Te (Gadd, 1993; Gharieb et al. 1995) which can be deposited intracellularly or extracellularly in nanoparticulate, -crystalline and -rod morphologies (Hockin and Gadd, 2003, 2006; Oremland et al. 2004; Baesman et al. 2007). However, almost all detailed research has been carried out with anaerobic selenate-respiring or sulfate-reducing bacteria (Hockin and Gadd, 2003, 2006). Surprisingly little information is available for Se or Te reduction in aerobic organisms although the capability seems ubiquitous (Gharieb et al. 1995). Further, almost nothing is known about geochemical influences and limitations on metalloid reduction in aerobic habitats. How can metalloid reduction proceed in such a complex environment as soil or sediment in the presence of multiple mineral phases, other redox-sensitive metal(loid)s, e.g. Fe, As, varying nutrient levels and organic content, and other organisms? WorkplanThe aim of this project is to examine geochemical influence on Se/Te reduction by aerobic microbes, using model systems of simple to intermediate complexity, in order to identify and understand what limitations there are to the process, and their importance. The influence of other metal and mineral components, organic components and nutrients on metalloid reductive capabilities of geoactive bacterial and fungal strains will be characterised, together with the abilities of strains to effect other metal-mineral transformations. Simple pure culture systems as well as mixed bacterial-fungal microcosms and simulated soil matrices will be used. Abiotic influence on the form and location of precipitated metalloids will also be investigated. The project will therefore produce fundamental scientific information regarding aerobic Se/Te reduction and its significance, and therefore add to our current understanding of Se/Te biogeochemistry. This project will use an interdisciplinary approach and the student will receive training in geomicrobiology and environmental mineralogy with associated analytical and preparative techniques, including growth and manipulation of experimental organisms, and techniques including atomic absorption spectrophotometry (AAS), X-ray powder diffraction (XRPD), and advanced light and electron microscopy, X-ray element analysis and mapping.