Ecophysiology of Vacuolate Marine Sulfur Bacteria

像Beggiatoa这样的大型液泡状硝酸盐积累细菌可以氧化各种海洋生态位中产生的大多数硫化物。密切相关的硫细菌（液泡附丝或VAF）不积累硝酸盐，在海洋硫化物喷口表面大量存在。总的来说，这些系统发育上一致的生物是已知的唯一含有液泡的变形菌门，很明显，它们在各种海洋环境的氮和硫循环中起着重要作用。Beggiatoa物种也是被称为“黑带病”的细菌联合体的成员，这种疾病构成了珊瑚的广泛和致命疾病。首席研究员从黑带病（菌株BBD）中分离出直径7微米的液泡Beggiatoa稳定培养物，该菌株积累硝酸盐，似乎能够固定二氮。该培养菌株和一些自然种群的VAF和硝酸盐积累Beggiatoa是本项目的重点。研究者将使用微电极和分子分析来了解液泡硫细菌亚群中硝酸盐与氧基硫化物呼吸的相对重要性。研究者将调查液泡状Beggiatoa spp.的垂直分布和丰度，确定液泡态硝酸盐如何影响固氮，并将获得和使用重要的氮循环基因（nifD， nifH和nrfA同源物）探针。除了培养一名研究生外，该项目还将通过与加州大学戴维斯分校生物学本科生学者计划的互动，专门针对弱势群体和代表性不足的本科生。

Large, vacuolate, nitrate-accumulating bacteria such as Beggiatoa can oxidize a majority of the sulfide produced in a variety of marine niches. Closely related sulfur bacteria (vacuolated attached filaments or VAF) that do not accumulate nitrate are abundant on surfaces at marine sulfidic vents. Collectively, these phylogenetically coherent organisms are the only Proteobacteria known to contain vacuoles and it is clear that they play a significant role in the nitrogen and sulfur cycles of a variety of marine environments. Beggiatoa species are also members of the bacterial consortium known as "black band disease" that constitutes a widespread and lethal disease of corals. The principal investigator has isolated a stable culture of a 7-micron diameter vacuolate Beggiatoa from black band disease (strain BBD) that accumulates nitrate and seems to be capable of dinitrogen fixation. This cultured strain and a number of natural populations of VAF and nitrate-accumulating Beggiatoa are the focus of this project. The investigator will use microelectrode and molecular analyses to understand the relative importance of nitrate- vs. oxygen-based respiration of sulfide in subgroups of vacuolate sulfur bacteria. The investigator will survey the vertical distribution and abundance of vacuolate Beggiatoa spp. and determine how vacuolar nitrate affects nitrogen fixation, and will derive and use probes of important nitrogen cycle genes (nifD, nifH and a nrfA homologue). In addition to training a graduate student, the project will specifically target disadvantaged and underrepresented undergraduates through interaction with the Biology Undergraduate Scholars Program at UC-Davis.