Ecophysiology and Phylogeny of Vacuolate, Nitrate-Accumulating Sulfur Bacteria

细胞内充满液体的膜结合空间，可能具有多种功能，包括储存。 直到最近，人们才明确指出细菌中不存在空泡。 然而，在最近的研究中，包括在PI实验室进行的NSF支持的研究，在属于Beggiatoa，Thioploca和Thiomargarita属的大型细菌中发现了空泡。 这些结构约占这些细胞生物体积的80%，据信与硝酸盐的积累和储存有关，在整个细胞体积上计算平均为0.1至0.5摩尔（高于环境水平10，000倍）。 储存的硝酸盐可以用作氧化剂，从而转化为氨，同时允许由硫化氢的厌氧氧化驱动的生物有用能量的产生。 这些硝酸盐积累细菌形成一个单一的进化集群，并从其他人的实地研究判断，它们可能在海洋氮循环中发挥重要的作用。 目前的研究将研究这些细菌的生态生理学和代谢，重点是Beggiatoa，并将空泡细菌的研究扩展到附着的丝状Thiothrix样菌株，这些菌株在华盛顿海岸和其他地方的深海热液喷口的各种表面上占主导地位。 将进行附着形式的研究，以确定它们与先前鉴定的空泡细菌之间的进化关系，并确定空泡是否在不同物种中起相同的生理作用。 为了更深入地研究空泡，硝酸盐还原，硫化物氧化细菌的生理生态学，将详细研究从蒙特雷峡谷富含硫化物的渗漏（900米深）中容易获得的Beggiatoa种群。 将确定它们使用氧和硝酸盐作为氧化剂的能力以及它们使用有机与无机细胞碳源的能力。 由于这些细菌在蒙特雷峡谷渗漏沉积物的上部15厘米处占主导地位，这些研究将通过分析细菌的丰度与深度的关系，结合研究硫化物、硫酸盐和氨的沉积物孔隙水剖面以及某些代谢抑制剂对沉积过程的影响，提供关于细菌原地代谢的信息。 没有空泡细菌曾经在纯培养中生长，但研究中的种群可以收获足够的纯度，以允许化学，酶学和分子表征。 研究人员将试图克隆编码贝贾托阿中心代谢过程的基因，并将采用分子程序来确定克隆的基因是否真的来自贝贾托阿。 对这种类型的分析最终可能使人们有可能了解细菌中空泡形成或空泡变性的遗传基础。 这为将这些看似理想的特性改造成其他培养细菌提供了长期的可能性

Vacuoles, fluid-filled membrane-bound spaces within cells, may serve a variety of functions, including storage. Until recently, it has been categorically stated that vacuoles do not occur in bacteria. In recent studies, however, including NSF-supported studies undertaken in the PI's laboratory, vacuoles have been discovered in large bacteria belonging to the genera Beggiatoa, Thioploca and Thiomargarita. These structures, which comprise roughly 80% of the biovolume of these cells, are believed to be involved in the accumulation and storage of nitrate, which averages 0.1 to 0.5 molar (10,000-fold above ambient levels) computed over the entire cell volume. The stored nitrate can serve as an oxidant, thereby being converted to ammonia while allowing the generation of biologically useful energy driven by the anaerobic oxidation of hydrogen sulfide. These nitrate-accumulating bacteria form a single evolutionary cluster, and, judging from field studies of others, they may play a quantitatively important role in the marine nitrogen cycle. The current research will examine the ecophysiology and metabolism of these bacteria, focusing on Beggiatoa, and will extend the study of vacuolate bacteria to attached, filamentous, Thiothrix-like strains that dominate the biomass on a variety of surfaces at deep-sea hydrothermal vents off the coast of Washington and elsewhere. Studies of the attached forms will be undertaken to determine the evolutionary relationships between them and the previously identified vacuolate bacteria, and to determine whether the vacuole serves the same physiological role in the diverse species. To delve more deeply into the ecophysiology of vacuolate, nitrate reducing, sulfide-oxidizing bacteria, Beggiatoa populations readily available from sulfide-rich seeps (900 m depth) in Monterey Canyon will be studied in detail. Their ability to use both oxygen and nitrate as oxidants as well as their ability to use organic vs. inorganic sources of cell carbon will be determined. Because these bacteria dominate the upper 15 centimeters of the Monterey Canyon seep sediments, these studies will yield information on the bacteria's in situ metabolism through analyses of their abundance vs. depth in conjunction with a study of sediment porewater profiles of sulfide, sulfate and ammonia and the influence of certain metabolic inhibitors on sediment processes. No vacuolate bacterium has ever been grown in pure culture, but the populations under study can be harvested in sufficient purity to allow chemical, enzymological and molecular characterizations. The investigators will attempt to clone the genes encoding the central metabolic processes in Beggiatoa and will employ molecular procedures to determine whether the cloned genes were actually derive from Beggiatoa. Analyses of this type may eventually make it possible to understand the genetic basis for vacuole formation or gigantism in bacteria. This offers the long-term possibility of engineering these seemingly desirable traits into other cultivated bacteria