The role of organic and metal cofactors on the biogenic synthesis of halogenated volatile hydrocarbons

挥发性卤化烃气体，在这种情况下是卤代甲烷，是由海洋中的生物自然产生的;海洋随后成为这些生物源气体进入大气的来源。它们在大气中的化学反应与人为产生的氯氟烃（CFC）非常相似。虽然CFC得到了很好的研究，因为它们消耗了高层大气中的臭氧，使地球免受有害的紫外线辐射，但卤代甲烷在很大程度上被忽视了，尽管它们目前占臭氧消耗的25%。 然而，随着人为的氟氯化碳水平稳步下降，预计到2050年，卤代甲烷将占臭氧消耗的50%。 根据迄今为止有限的研究，海洋卤代甲烷的产生主要归因于浮游植物和大型藻类。该项目将建立在新的和令人信服的数据基础上，这些数据表明海洋异养细菌也可能是卤代甲烷的主要生产者。 这里产生的数据将提供解决全球卤代甲烷预算差异所需的关键评估，目前由于大气中的未知来源而失去平衡，评估海洋异养细菌可以提供这种缺失来源的假设。对地球平流层臭氧层稳定性的关注使得这项有价值和必要的研究具有为南加州大学从事的本科生、研究生和博士后教育提供支持的附加价值。过去关于海洋卤甲烷产生的研究集中在浮游植物和大型藻类上，而潜在的细菌对该过程的贡献被忽视了。本研究拟探讨海洋异养细菌对卤代甲烷产生的影响。在过去的研究中已经注意到，全球大气中的卤代甲烷收支存在差异，这可能是由于大量细菌来源的缺失。此外，这项研究将评估维生素B12，蛋氨酸和钒辅因子对细菌中卤代甲烷合成的潜在重要性。大部分海洋细菌不能合成甲基化辅酶，因此需要来自外部来源的B12，蛋氨酸和钒来完成甲基化步骤。本研究还将测量上升流区域以及长期时间序列站点中卤代甲烷、B12、蛋氨酸和钒的浓度，以便对用于全球关联海气模型的卤代甲烷浓度的变异性施加限制。

Volatile halogenated hydrocarbon gases, in this case halomethanes, are produced naturally by organisms in the ocean; which then serves as a source of these biogenic gases to the atmosphere. Their chemical reactions in the atmosphere are very similar to those of anthropogenic chlorofluorocarbons (CFCs). While CFCs are well-studied because they consume the ozone in the upper atmosphere that shields the earth from harmful ultraviolet radiation, halomethanes have been largely neglected, even though they currently account for 25% of the ozone depletion. As anthropogenic CFC levels steadily decline, however, halomethanes are predicted to account for 50% of ozone depletion by 2050. Based on limited study thus far, marine halomethane production has been ascribed mainly to phytoplankton and macro algae. This project will build on new and compelling data that suggests marine heterotrophic bacteria could also be major producers of halomethanes. The data produced here will provide the critical evaluation required to address discrepancies in global halomethane budgets which currently are out of balance due to an unknown source to the atmosphere, evaluating the hypothesis that marine heterotrophic bacteria can supply this missing source. Concerns over the stability of the earth's stratospheric ozone layer make this valuable and necessary research with added value of providing support for engaged undergraduate, graduate, and postdoctoral education at the University of Southern California.Past research on the production of marine halomethanes has focused on phytoplankton and macro algae, while potential bacterial contributions to the processe have been neglected. This research proposes to study the role of marine heterotrophic bacteria on the production of halomethanes. It has been noted in past studies that there are discrepancies in the global atmospheric halomethane budget, and it is possible this is due to a large missing bacterial source. Additionally, this research will evaluate the potential importance of vitamin B12, methionine, and vanadium cofactors on the synthesis of halomethanes in bacteria. A large portion of marine bacteria cannot synthesize methylation co-enzymes, and therefore, would require available B12, methionine, and vanadium from external sources to complete the methylation step. This study will also measure concentrations of halomethanes, B12, methionine, and vanadium in upwelling regions as well as at a long-term time series site in order to put constraints on the variability of halomethanes concentrations for use in global linked air-sea models.