ARSENIC AND OLD LIFE: NOVEL GEOBIOCHEMISTRY OF ARSENIC IN BIOLOGICAL SYSTEMS

这个子项目是许多利用资源的研究子项目之一 由NIH/NCRR资助的中心拨款提供。子项目的主要支持 而子项目的主要调查员可能是由其他来源提供的， 包括其它NIH来源。 列出的子项目总成本可能 代表子项目使用的中心基础设施的估计数量， 而不是由NCRR赠款提供给子项目或子项目工作人员的直接资金。 我们研究的重点是确定和描述一个以砷为基础的生命的实例，这当然是一个高风险但非常有趣的研究，由NASA NAI资助。到目前为止，我们已经使用了富含砷，高盐度和高碱性的沃茨，加利福尼亚州莫诺湖，以寻找这种不寻常的生物。我们目前的状态是，我们已经丰富，分离和确定（16 S rDNA）的γ-变形菌的成员，已知的生物积累砷。我们通过电感耦合等离子体质谱法（ICP-MS）证实，在仅向培养基中添加5 mM砷酸盐且不添加磷酸盐的生长条件下，该菌株的As/P比几乎为7;然而，该菌株也可以仅用磷酸盐和磷酸盐与砷酸盐组合生长，分别导致令人放心的As/P比为0.001和0.010。此外，我们目前正在测量放射性标记的73 As砷酸盐的摄取，以确认各种阴离子营养条件下的摄取率，但我们的数据表明，开发细胞内砷含量和有和无砷酸盐或磷酸盐生长的细胞形态的全面图片将大大加强我们的故事。

This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. Primary support for the subproject and the subproject's principal investigator may have been provided by other sources, including other NIH sources. The Total Cost listed for the subproject likely represents the estimated amount of Center infrastructure utilized by the subproject, not direct funding provided by the NCRR grant to the subproject or subproject staff. The focus of our study, that is the identification and characterization of a living example of arsenic-based life, is certainly a high risk but exceedingly interesting study as funded by the NASA NAI. Thus far we have used the arsenic-rich, hypersaline and highly alkaline waters of Mono Lake, CA to hunt for such an unusual organism. Our current status is that we have enriched for, isolated and identified (by 16s rDNA) a member of the gamma-Proteobacteria that are known to bioaccumulate arsenic. We confirmed by Inductively Coupled Plasma Mass Spectrometry (ICP-MS) that under growth conditions in which ONLY 5 mM arsenate was amended to the medium and NO phosphate was added this strain has a As/P ratio of almost 7; however this strain can also grow with phosphate only and phosphate combined with arsenate leading to the reassuring As/P ratios of 0.001 and 0.010, respectively. In addition, we are currently measuring the uptake of radiolabeled 73As arsenate to confirm the rate of uptake under a variety of anionic nutrient conditions, but our data indicate that developing a comprehensive picture of the intracellular arsenic content and speciation of cells grown with and without arsenate or phosphate would greatly strengthen our story.