LEXEN: Microbial Adaptation to High Temperature and Pressure

LEXEN：微生物对高温高压的适应

• 批准号: 9809352
• 负责人: Frank Robb
• 金额: --
• 依托单位: University of Maryland Biotechnology Institute
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 1998
• 资助国家: 美国
• 起止时间: 1998-10-01 至 2002-09-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=9809352&HistoricalAwards=false
• 关键词: LEXEN; Microbial; Adaptation; Temperature; Pressure

Hyperthermophilic microorganisms may be suitible models for ancestral, and possibly extraterrestrial, biosystems because their extraordinary adaptive capabilities allow them to colonize a wide range of subsurface volcanic areas on Earth. Deep sea hydrothermal vents and terrestrial hot springs support highly diverse ecosystems without access to solar energy, harboring autotrophic microorganisms and their dependant heterotrophic micro- and macro communities in geochemical conditions similar to those that may exist below the surface of Mars or Europa. Hyperthermophiles also dominate most of the deeper branches of the universal phylogenetic tree, suggesting that ancestral microorganisms may have been thermophilic. The environmental limits for growth and survival of known hyperthermophilic species, as well as newly isolated strains will be established, using a combination of bioengineering, microbiology and molecular biology. This collaborative project with Dr. Douglas S. Clark of the University of California, Berkeley (Award 9816490) emphasizes molecular adaptations to high pressure and high temperature, with the following objectives: 1. To determine the effects of supraoptimal temperatures and pressures on the survival and growth rates of existing hyperthermophilic microorganisms;2.To utilize pressurized continuous fermentation systems for isolation and culture of new hyperthermophilic microbial strains and; 3. To examine physiological adaptations and genetic regulation of gene expression in response to transient challenges by heat and high pressure. The hypothesis being tested is that hydrostatic pressure may greatly extend the upper temperature limits of growth and survival of hyperthermophiles. Ongoing studies by these researchers have established that many enzymes from thermophiles display enhanced thermostability under pressure. Further, the growth rate of Methanococcus jannaschii accelerated five-fold and its maximum temperature for methane production rose by 6 degrees C in response to pressure, and the growth rate and ATP production of a newly characterized abyssal hyperthermophile, Pyrococcus horikoshii, were elevated under pressure. Novel equipment for incubating hyperthermophiles in continuous culture, under pressure and with thermal cycling, will be combined with molecular biology to explore the adaptive responses of hyperthermophiles in extremis. Gene expression, membrane lipid composition and morphology will be examined. The genes that are induced under conditions approaching lethality, will be identified by subtractive cloning and transcriptional assays. Upper survival limits of the abyssal hyperthermophiles as a function of pressure, using isolates from a shallow terrestrial sampling site to provide control data for pressure responses, will be determined. Enrichment cultures of hyperthermophiles from the vent systems of the back-arc region of the Northwest Pacific (Okinawa Trough and Uzzon Caldera on the Kamchatka Peninsula) will be incubated at temperatures and pressures exceeding those tolerated by known strains, thus using survival rather than rapid growth as the criterion for selection of new isolates. The phylogenetic positions and physiological requirements of the new strains will be determined.

超嗜热微生物可能是祖先的合适模型，也可能是外星生物系统，因为它们非凡的适应能力使它们能够在地球上广泛的地下火山地区定居。深海热液喷口和陆地温泉在没有太阳能的情况下维持着高度多样化的生态系统，在类似于火星或木卫二表面以下可能存在的地球化学条件下，拥有自养微生物及其依赖的异养微型和大型群落。超嗜热菌也主宰了通用系统发育树的大部分深层分支，这表明祖先微生物可能是嗜热的。将结合使用生物工程、微生物学和分子生物学，确定已知极端嗜热菌种以及新分离菌株的生长和存活的环境限制。这个与道格拉斯S.克拉克的加州大学伯克利分校（奖9816490）强调分子适应高压和高温，有以下目标：1。确定超适温度和压力对现有超嗜热微生物存活和生长速率的影响; 2.利用加压连续发酵系统分离和培养新的超嗜热微生物菌株; 3.研究高温和高压对基因表达的生理适应和遗传调控。 正在测试的假设是，静水压力可能会大大延长超嗜热菌生长和生存的温度上限。这些研究人员正在进行的研究已经确定，许多来自嗜热菌的酶在压力下显示出增强的热稳定性。此外，甲烷球菌jannaschii的生长速度加快了5倍，其甲烷生产的最高温度上升了6摄氏度，以响应压力，和一个新的特征的深海超嗜热菌，Pyrococcus horikoshii的生长速度和ATP的生产，在压力下升高。用于在压力和热循环下连续培养超嗜热菌的新型设备将与分子生物学相结合，以探索极端条件下超嗜热菌的适应性反应。将检查基因表达、膜脂质组成和形态。将通过消减克隆和转录测定鉴定在接近致死性的条件下诱导的基因。 将利用从一个浅层陆地取样点分离的微生物作为压力反应的对照数据，确定深海超嗜热菌的生存上限与压力的关系。来自西北太平洋弧后地区（堪察加半岛的冲绳海槽和Uzzon火山口）的喷口系统的超嗜热菌的富集培养物将在超过已知菌株所能耐受的温度和压力下进行培养，从而使用生存而不是快速生长作为选择新菌株的标准。将确定新菌株的系统发育位置和生理要求。