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

挥发性卤化碳氢化合物气体，在这种情况下是卤代甲烷，由海洋中的生物自然产生；然后作为这些生物来源气体的来源进入大气。它们在大气中的化学反应与人造氯氟烃(CFCs)的化学反应非常相似。虽然对氯氟烃的研究很多，因为它们消耗高层大气中的臭氧，使地球免受有害的紫外线辐射的伤害，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，随着人为的氯氟化碳水平稳步下降，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必要的关键评估，以解决全球卤代甲烷预算中的差异，这些差异目前由于大气中的未知来源而失衡，评估海洋异养细菌可以补充这一缺失来源的假设。对地球平流层臭氧层稳定性的担忧使这项有价值和必要的研究具有附加值，为南加州大学的本科生、研究生和博士后教育提供支持。过去对海洋卤代甲烷产生的研究主要集中在浮游植物和大型藻类上，而忽略了细菌对这一过程的潜在贡献。这项研究建议研究海洋异养细菌在卤代甲烷生产中的作用。过去的研究指出，全球大气中的卤代甲烷预算存在差异，这可能是由于大量缺少细菌源所致。此外，这项研究将评估维生素B12、蛋氨酸和钒辅助因子在细菌中合成卤代甲烷的潜在重要性。很大一部分海洋细菌不能合成甲基化辅酶，因此，需要从外部来源获得B12、蛋氨酸和钒来完成甲基化步骤。这项研究还将测量上升流区和长期时间序列地点的卤代甲烷、B12、蛋氨酸和钒的浓度，以便限制用于全球联系的大气-海洋模式的卤代甲烷浓度的可变性。

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.