Life in an Ultra-basic and Ultra-reducing Setting: The Cedars Serpentinization Communities

该项目的重点是雪松橄榄岩，在北方加州的一个网站，活跃的蛇纹石化发生，导致春季沃茨如此极端，没有目前的微生物代谢的范例与那里存在的生命兼容。 因此，这项工作的智力驱动力围绕着理解微生物如何设法在这种极端无机的超碱性（pH ~ 12）水世界中维持生计，这种水具有：1）异养生长的有机碳水平低; 2）（在该pH下）几乎没有溶解的CO2或碳酸氢盐用于自养碳吸收; 3）Eh通常低于-550 mV; 4）没有明显丰富的电子受体;（5）低Na+水平。H+的缺乏和Na+的低浓度表明，存在于这种环境中的微生物具有可能不同于先前描述的任何东西的能量代谢。因此，识别和表征常驻微生物及其利用的代谢方法可能使我们能够理解微生物（个体和/或互养群体）如何利用乍一看似乎不可能居住的环境。 研究人员将研究几种不同高pH池的微生物学，在两年的项目中有以下目标：1）通过16 S rDNA表征和宏基因组测序鉴定优势微生物物种; 2）通过宏基因组学和基因组组装表征环境和生物基因含量; 3）通过元转录组学确定这些基因中的哪些基因被表达和/或激活，以及4）地点的地球化学表征，使得生物数据可以被置于地球化学背景中。 这种方法是在测试哪些菌株在这种恶劣的生态系统中生长以及它们如何生长（即，利用哪些代谢机制和途径）。 它还涉及到一个问题，即真正定义一个成功的生态系统的是基因含量还是物种含量（或两者兼而有之）。 该项目将导致确定在这种恶劣环境中生存和生长所需的基因类型：例如，细胞色素、ATP酶、氢化酶、阳离子泵等。初步结果显示，有一些优势物种，但多样性很低。 16 S rRNA基因序列分析的结果表明，这些微生物与以前发现的任何微生物都不同，考虑到这些位点的代谢挑战，这也许并不奇怪。 这项工作的结果还将提供对当今地球上微生物生命适应和进化的深入了解，鉴于这些超碱性厌氧环境与光合作用活动之前的早期地球条件非常相似，这些结果可能对早期地球上生命的适应和进化具有重要意义。因此，研究人员希望这些结果不仅有助于更好地了解极端微生物（这些数据可能在了解新型碱性微生物群落方面提供里程碑），而且有助于早期地球生命的模型。 该项目将包括实地和实验室工作，将由一名博士后研究员，一名研究生和几名本科生进行。

This project focuses on The Cedars Peridotite, a site in Northern California where active serpentinization occurs, resulting in spring waters so extreme that no current paradigms of microbial metabolism are compatible with life existing there. The intellectual driver of the work thus revolves around the understanding of how microbes manage to eke out a living in this extreme inorganic world of ultra-basic (pH ~ 12) water that has: 1) low levels of organic carbon for heterotrophic growth; 2) (at this pH) virtually no dissolved CO2 or bicarbonate for autotrophic carbon uptake; 3) an Eh that is routinely lower than -550 mV; 4) no obvious abundant electron acceptors; and, 5) low levels of Na+. The absence of H+ and the low concentration of Na+ suggest that the microbes present in this environment are equipped with an energy metabolism that is potentially unlike anything previously described. Thus, identifying and characterizing the resident microbes and the metabolic approaches they utilize may allow us to form an understanding for just how microbes (individuals and/or syntrophic groups) can exploit an environment that appears, at first glance, to be impossibly inhospitable. Investigators will study the microbiology of several different high pH pools, with the following goals in the two year project: 1) the identification of the dominant microbial species by 16S rDNA characterization and metagenomic sequencing; 2) the characterization of the environmental and organismal gene content by metagenomics and genome assembly; 3) the determination of which of these genes are expressed and/or active by metatranscriptomics, and, 4) the geochemical characterization of the sites, so that the biological data can be placed in a geochemical context. This approach is a necessary first step towards hypothesis generation in terms of testing which strains grow in this harsh ecosystem, and how they do it (i.e., which metabolic mechanisms and pathways are utilized). It also relates to the question of whether it is the gene content or the species content (or both) that truly defines a successful ecosystem. This project should lead to the identification of the types of genes required for survival and growth in this harsh environment: e.g., cytochromes, ATPases, hydrogenases, cation pumps, etc. Preliminary results have revealed a number of dominant species and very low diversity. Results of 16S rRNA gene sequence analyses suggest that these microbes are distinct from any previously seen microbes, perhaps not surprising, given the metabolic challenges in these sites. The results of this work will also provide insight into the adaptation and evolution of microbial life on present-day Earth, and given that these ultra-basic, anaerobic environments are close analogs to the early earth conditions prior to photosynthetic activity, the results may have significance regarding the adaptation and evolution of life on the early Earth. Investigators thus expect these results to significantly contribute to a greater understanding not only of extremophiles (the data may provide a milestone in terms of understanding a new type of alkaline microbial community), but to models of early earthly life. The project, which will include both field and laboratory work, will be carried out by a postdoctoral fellow, a graduate student, and several undergraduates.