EAGER: Iron-Virus Interactions in the Ocean

EAGER：海洋中铁与病毒的相互作用

• 批准号: 1722761
• 负责人: Kristen Buck
• 金额: $ 29.93万
• 依托单位: University of South Florida
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2017
• 资助国家: 美国
• 起止时间: 2017-02-01 至 2020-01-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1722761&HistoricalAwards=false
• 关键词: EAGER; Iron; Virus; Interactions; Ocean

Iron is an essential micronutrient for phytoplankton that is required for photosynthesis and respiration. Insufficient iron has been shown to limit phytoplankton growth in large regions of the surface ocean, and correspondingly, iron cycling is directly linked to carbon cycling in much of the marine environment. Nearly all iron in seawater (99%) exists as complexes with organic molecules called ligands, which govern the concentration of iron dissolved in the water and the bioavailability of that iron to phytoplankton. However, despite the importance of iron-binding organic ligands, their sources and identities are largely unknown. Viruses, the majority of which are phages (viruses that infect bacteria), are extremely abundant in seawater and are in the same size fraction as dissolved iron. Recent evidence that non-marine phages contain iron as part of their structures has led to the proposal that marine phages may represent a previously overlooked class of organic iron-binding ligands. This project is determining the contribution of marine phages to dissolved iron pools and culture phage-host systems in the laboratory to determine if phages utilize bacterial iron-uptake receptors for infection in the manner of a Trojan horse. As the first study to examine the biogeochemical impact of trace elements contained within the structure of highly abundant marine phage particles, successful completion of the proposed research will be transformative for biological and chemical oceanography and have far-reaching implications for other fields, including human health where iron availability plays an important role in microbial pathogenesis. This project contributes to the multidisciplinary training of a graduate student and postdoctoral researcher. Research results will be disseminated through scientific publications and presentations, and the public will be educated about linkages between viruses and ocean chemistry via a hands-on exhibit for the annual St. Petersburg Science Festival. Building upon evidence from non-marine model systems demonstrating the presence of iron ions in phage tail proteins and phage utilization of cell surface receptors for siderophore-bound iron, this project combines field and laboratory-based experiments to test the following three hypotheses regarding iron-virus interactions in the oceans: (1) Iron incorporated into phage tails originates from bacterial cell reserves, reducing the amount of iron available for remineralization upon lysis; (2) Phages constitute important iron-binding ligands in the oceans, accounting for a substantial portion of organically complexed colloidal dissolved iron; (3) Marine phages compete with siderophore-bound iron for uptake receptors on the bacterial cell surface and use iron in their tails as a Trojan horse for infection. Initial calculations predict that phages could account for up to 70% of the colloidal fraction of organically complexed dissolved iron in the surface ocean; therefore, this project is critical for advancing knowledge of trace-metal cycling as well as phage-host interactions. Additionally, if a portion of the cellular iron thought to be released from bacterial cells for remineralization following lysis is already incorporated into phage tails, then these findings will have significant implications for oceanic biogeochemical models. Through a combination of laboratory-based culture experiments and field sample measurements, this project could reveal the identity of a ubiquitous component of colloidal organic iron-binding ligands, modify the estimates of iron concentrations and species released through viral lysis, and potentially identify a novel receptor type for marine phage that may compete with the acquisition of siderophore-bound iron by host bacteria.

铁是光合作用和呼吸所需的浮游植物的必不可少的微量营养素。已经证明铁不足可以限制地表海洋大区域的浮游植物生长，相应地，铁循环直接与大部分海洋环境中的碳循环有关。海水中几乎所有铁（99％）的存在是与称为配体的有机分子的复合物，该配体控制了溶解在水中的铁的浓度以及该铁对浮游植物的生物利用度。但是，尽管有机配体具有重要性，但它们的来源和身份在很大程度上尚不清楚。病毒，大多数是噬菌体（感染细菌的病毒），在海水中非常丰富，并且与溶解的铁的尺寸相同。最近的证据表明，非海洋噬菌体含有铁作为其结构的一部分，这导致了海洋噬菌体可能代表先前被忽视的有机铁结合配体的提议。该项目正在确定实验室中海洋噬菌体对溶解铁池和培养噬菌体托管系统的贡献，以确定噬菌体是否利用细菌铁摄取受体以特洛伊木马的方式感染。作为首次研究在高度丰富的海洋噬菌体颗粒结构中包含的痕量元素的生物地球化学影响的研究，成功完成拟议的研究将对生物学和化学海洋学的变化进行变革，并且对其他领域具有深远的影响，包括对人类健康在微生物病原体中起重要作用。该项目为研究生和博士后研究员的多学科培训做出了贡献。研究结果将通过科学出版物和演讲传播，将通过举办年度圣彼得堡科学节的动手展览来教育公众关于病毒与海洋化学之间的联系。 Building upon evidence from non-marine model systems demonstrating the presence of iron ions in phage tail proteins and phage utilization of cell surface receptors for siderophore-bound iron, this project combines field and laboratory-based experiments to test the following three hypotheses regarding iron-virus interactions in the oceans: (1) Iron incorporated into phage tails originates from bacterial cell reserves, reducing the amount of iron available for remineralization upon lysis; （2）噬菌体构成了海洋中重要的铁结合配体，这是有机复合的胶体溶解铁的很大一部分； （3）海洋噬菌体与辅助载体结合的铁竞争细菌细胞表面的摄取受体，并将铁作为特洛伊木马作为感染。 初始计算预测，噬菌体最多可以占表面海洋中有机溶解的铁的胶体分数的70％。因此，该项目对于促进痕量 - 金属循环以及噬菌体宿主相互作用的知识至关重要。此外，如果已经将一部分被认为是从细菌细胞中释放出的细胞铁，以使裂解后的再矿化释放为噬菌体尾巴，那么这些发现将对海洋生物地球化学模型产生重大影响。通过基于实验室的培养实验和现场样本测量的组合，该项目可以揭示胶体有机铁结合配体无处不在的成分的身份，修改了通过病毒裂解释放的铁浓度和物种的估计，并有潜在地识别出可能与可能与BAC批准的海洋噬菌体相竞争的新型受体噬菌体。

项目成果

Phage puppet masters of the marine microbial realm

• DOI: 10.1038/s41564-018-0166-y
• 发表时间: 2018-07-01
• 期刊: NATURE MICROBIOLOGY
• 影响因子: 28.3
• 作者: Breitbart, Mya;Bonnain, Chelsea;Sawaya, Natalie A.
• 通讯作者: Sawaya, Natalie A.