ADAPTATIONS OF UNICELLULAR EUKARYOTES TO EXTREMELY ACIDIC ENVIRONMENTS

这个子项目是利用由NIH/NCRR资助的中心拨款提供的资源的许多研究子项目之一。子项目和调查员(PI)可能从另一个NIH来源获得了主要资金，因此可能会出现在其他CRISE条目中。列出的机构是针对中心的，而不一定是针对调查员的机构。对极端环境的研究很少针对真核生物，因为生物学家通常认为它们的多样性较低，无法在恶劣条件下生长。生长在富含铁的里约热内卢的真核生物可能为在极端条件下生存所需的新的生理适应提供线索，例如酸性矿山排水系统或火星上可能存在的外星生态系统。使用分子方法和BRC提供的功能分析相结合的方法，我们已经开始解开允许有机体在这些极端环境中生存的适应策略。也许最有趣的问题包括：真核生物如何在如此强烈的H+离子浓度梯度下生存下来，以及它们如何在相对较短的进化时间内适应这些条件？除非生活在酸性环境中的质子体的内部pH低于6.5，否则它们必须进化出阻止质子自由扩散到细胞内的机制。我们正试图确定真核生物在低pH值下生存所需的离子调节机制，包括离子泵和离子转运体，并探索它们的多样性和从力拓分离的原生生物的进化史。我们推测，在各种嗜酸性原生生物中，ATPase的多样性使这些生物能够适应极端环境。NCRR BioCurrents研究中心使用的资源：生理实验使用先进的成像技术来评估和确认力拓分离株及其来自标准培养集合的近亲的细胞内pH水平。使用BRC培养设施来维护微生物。光合作用绿藻衣藻的综合研究。(力拓分离株RT1no2)表明胞液pH值相对中性。嗜食性的Vannella sp.(Rio Tinto分离株Vn4)在胞外pH为2的情况下保持碱性胞液pH。胞液pH范围为7.2-7.8。这些梯度提出了一个问题，即这种差异是如何在膜和体壁上保持的。

This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. Few investigations of extreme environments target eukaryotes because biologists generally consider them to be less diverse and incapable of growing in hostile conditions. Eukaryotes growing in the iron-rich Rio Tinto may provide clues about novel physiological adaptations necessary for survival in extreme conditions, such as acid mine drainages or in extraterrestrial ecosystems that may exist on the planet Mars. Using a combination of molecular approaches with the functional assays available through the BRC we have begun to unravel the adaptive strategies that allow organisms to live in these extreme environments. Perhaps the most interesting questions include: How do eukaryotes survive such a strong H+ ion concentration gradient and how did they adapt to these conditions over relatively short periods of evolutionary time? Unless the internal pH of protists living in acid environments is lower than 6.5, they must have evolved mechanisms to prevent protons from freely diffusing into the cell. We are trying to identify the kinds of ion regulatory machinery including ion pumps and porters required for survival of eukaryotes at low pH, and to explore their diversity and evolutionary history in protists isolated from the Rio Tinto. We hypothesize that a diversity of ATPases in a variety of acidophilic protists have allowed these organisms to adapt to extreme environments. NCRR BioCurrents Research Center resource used: Physiological experiments use advanced imaging techniques to assess and confirm intracellular pH levels for the Rio Tinto isolates, as well as for their closest relatives from standard culture collections. BRC culture facilities are used to maintain the organisms. A comprehensive study of the photosynthetic green alga Chlamydomonas sp. (Rio Tinto Isolate RT1no2) indicates a relatively neutral cytosolic pH. The phagotrophic Vannella sp. (Rio Tinto Isolate Vn4) maintains an alkaline cytosolic pH in extracellular pH 2. The cytosolic pH range is 7.2-7.8. These gradients raise questions about how such differentialds are maintained across the membrane and body wall.