Collaborative Research: Biological controls on reactive oxygen species in the oligotrophic ocean

人们一直认为，光氧化的显色性溶解有机物是超氧化物（O2-）和过氧化氢（H2O2）的主要来源；然而，有迹象表明，生物来源可能在这些活性氧（ROS）的产生中起着重要的作用，如果不是主要的作用。由于开放海洋中这些ROS的存在会影响铁、铜和锰的氧化还原循环，从而影响它们的生物利用度，并且H2O2已被证明可以抑制混合层中原绿球藻生态型的生长，因此了解对O2-和H2O2的生物控制非常重要。为此，科罗拉多矿业学院和哈佛大学的科学家将测试以下假设：(1)暗生物生产是H2O2和O2-对低营养地表水的重要贡献；(2)生物生产和分解速率的时空变化导致了H2O2浓度的变化；(3)低营养水体中H2O2的生物生成是通过O2-的形成进行的，O2-的H2O2产率是可变的，取决于O2-的主要汇反应（例如与金属的反应）；(4)系统发育和生态多样性不同的细菌群，包括蓝藻和异养菌，其NADH（烟酰胺腺嘌呤二核苷酸）氧化酶的活性是海水ROS的重要来源。为了验证前三个假设，我们将在北太平洋亚热带少营养水域进行一系列野外观测，以确定H2O2和O2-的生物产率，并评估它们与光化学产率和光区H2O2浓度的关系。此外，还将进行实验室研究，以检查在不同氧汇存在的情况下，从O2-中产生H2O2的化学计量产量。对于假设4，将确定参与ROS产生的微生物的多样性，以及所涉及的蛋白质，这将有助于解释社区水平的转录组数据，以说明生物活性对ROS产生的可变贡献。关于更广泛的影响，主要支持者计划在科罗拉多专业发展科学会议上就生物地球化学循环的重要性发表演讲。如果成功收到，她建议将这些材料开发成一个为期一天的研讨会，并通过科罗拉多矿业学院教师提升计划提供。科罗拉多矿业学院的一名博士后和一名研究生以及哈佛大学的一名博士后、一名研究生和一名本科生将作为该项目的一部分得到支持和培训。

It has been assumed that photo-oxidation of chromophoric dissolved organic matter is the primary source of superoxide (O2-) and hydrogen peroxide (H2O2); however, there are indications that biological sources may play a significant, if not dominant, role in the production of these reactive oxygen species (ROS). Because the presence of these ROS in the open ocean can affect the redox cycling of iron, copper, and manganese which thereby influencing their bioavailability and H2O2 has been shown to inhibit the growth of Prochlorococcus ecotypes in the mixed layer, it is important to understand the biological controls on O2- and H2O2. For this reason, scientists at the Colorado School of Mines and Harvard University will test the following hypotheses: (1) dark biological production is an important contribution of H2O2 and O2- to oligotrophic surface waters; (2) spatial and temporal variations in biological production and decomposition rates contribute to the observed variability in H2O2 concentrations; (3) biological production of H2O2 in oligotrophic waters proceeds via formation of O2-, and the yield of H2O2 from O2- is variable depending on the major sink reactions (e.g. with metals) of O2-; and (4) activities of NADH (nicotinamide adenine dinucleotide) oxidase enzymes from a phylogenetically and ecologically diverse group of bacteria, including cyanobacteria and heterotrophs, are significant sources of ROS to marine waters. To test the first three hypotheses, a series of field observations in oligotrophic waters of the subtropical North Pacific will be carried out to establish biological production rates of H2O2 and O2- and assess their relationship to photochemical production and H2O2 concentrations in the euphotic zone. In addition, laboratory studies will also be conducted to examine the stoichiometric yield of H2O2 from O2- in the presence of different O2- sinks. For hypothesis 4, the diversity of microorganisms involved in ROS production will be identified, as well as the proteins involved which will enable the interpretation of community-level transcriptomic data for regions illustrating variable contributions of biological activity to ROS production.As regards broader impacts, the lead proponent plans to present a lecture at the Colorado Science Conference for Professional Development on the importance of biogeochemical cycles. If successfully received, she proposes to develop this material into a one day workshop and offer it via the Colorado School of Mines Teacher Enhancement Program. One postdoc and one graduate student from the Colorado School of Mines and one postdoc, one graduate student, and one undergraduate student from Harvard University would be supported and trained as part of this project.