Marine Biotech Fellowship: The Development and Use of Molecular Genetic Techniques for the Study of Fe Reduction in a Marine Eubacterium

生理数据表明，腐烂希瓦氏菌利用氧化剂的热力学层次结构可以单独编写，从缺氧区有氧生长到亚氧/缺氧海洋盆地和孔隙水无硫化物区和亚硫酸盐区交界的硫代硫酸盐还原。由于其多用途的碳代谢和兼性性质，腐烂链球菌和像它这样的生物可能会在海洋缺氧盆地和沉积孔隙水中与硫酸盐还原细菌竞争硫代硫酸盐和其他硫中间体。这些生物可能在控制海洋环境中硫的形成中起着重要作用。通过利用有机碳和产生硫化物，这些生物将密切参与到趋化素的平衡中。该项目将为广泛分布和用途广泛的厌氧呼吸生物的分子遗传学提供新的基础科学数据。通过分离和测序硫还原酶编码基因，本项目将能够研究基因表达的调控机制。在体内操作这些基因将有助于更好地理解腐臭葡萄球菌和其他海洋真细菌中各种硫还原途径之间的关系。遗传操作还可以帮助比较硫还原酶活性与硝酸还原酶或铁还原酶的调节。这项工作将导致合作开发一种利用天然沉积物中硫中间体的非硫酸盐还原细菌探针。该探针以及硫中间还原机制的数据可用于探索非硫酸盐还原细菌（如S. putrefaciens）在这些硫物种存在的各种亚/缺氧海洋环境中对S， Fe和C的地球化学的潜在贡献。

Physiological data suggest that a thermodynamic hierarchy for the utilization of oxidants could be written for Shewanella putrefaciens alone from aerobic growth in the oxic zone to thiosulfate reduction at the interface between sulfide-free and sulfitic zones of suboxic/anoxic marine basins and porewaters. With its versatile carbon metabolism and facultative nature, S. putrefaciens and organisms like it may well out compete sulfate- reducing bacteria for the consumption of thiosulfate and other sulfur intermediates in marine anoxic basins and sedimentary porewaters. These organisms may play a substantial role in the control of sulfur speciation in the marine environment. By utilizing organic carbon and producing sulfide, these organisms would be intimately involved in the poise of the chemocline. This project will provide new, basic scientific data on the molecular genetics of a widespread and very versatile anaerobic- respiring organism. By isolating and sequencing genes that code for sulfur reductase, this project will be able to study the regulatory mechanisms of gene expression. Manipulation of the genes in vivo will lead to a better understanding of the relationships between the various sulfur reduction pathways in S. putrefaciens and possibly other marine eubacteria. Genetic manipulation could also aid in comparing the regulation of sulfur reductase activity to that of nitrate reductase or Fe reductase in S. putrefaciens. This work will lead to the collaborative development of a probe for nonsulfate-reducing bacteria which utilize sulfur intermediates in natural sediments. Such a probe along with data on the mechanism of sulfur intermediate reduction could be used to explore the potential contribution of nonsulfate-reducing bacteria such as S. putrefaciens to the geochemistry of S, Fe, and C in a variety of suboxic/anoxic marine environments where these sulfur species exist.