Collaborative Research: Building a framework for the role of bacterial-derived chemical signals in mediating phytoplankton population dynamics

细菌和浮游植物在海洋环境中物质和营养物的改变和流动方面发挥着核心作用。虽然已经确定这两个域之间的相互作用是复杂的，但支持这些相互作用的机制在很大程度上仍然未知。然而，人们越来越认识到，溶解的化学信号控制着这些微生物的相互作用。该项目的重点是建立一个机制框架，细菌衍生的信号分子如何影响浮游植物和细菌之间的相互作用。群体感应（QS）分子，2-庚基-4-喹诺酮（HHQ）将被用作这些研究的模型化合物。先前发表的研究表明，接触极低水平的HHQ会导致浮游植物死亡。获得这些生态上重要的相互作用的机制的理解将有助于通知通过海洋微生物循环的材料的准确预测的数学模型。这项工作启动了一个新的，混合车间实习本科生化学生态学研究计划，重点是细菌浮游植物的相互作用。本科生参加一个激烈的夏季学习体验，其中研究和基于实地的练习补充了基于短期讲座的模块。学生回到自己的家乡机构，并与PI密切合作，进行与夏季研究的目标和范围有关的跨学科研究。这项研究还为两名研究生和一名博士后科学家提供了培训和职业发展。浮游植物和细菌之间的相互作用在介导海洋地球化学循环和微生物营养结构中起着核心作用。这两个生命领域之间的复杂关系是通过分泌的分子介导的，这些分子促进了交流并决定了竞争结果。尽管它们具有预测的重要性，但识别这些释放的化合物仍然是一个挑战。PI最近发现了一种细菌QS分子HHQ，由全球分布的海洋γ-变形菌产生，导致浮游植物死亡。因此，PI假设细菌QS信号是浮游植物种群动态的关键驱动因素，并最终导致地球化学通量。本项目调查了HHQ产生的时间和幅度，以及敏感浮游植物物种对HHQ暴露的生理和转录组学反应，并量化了HHQ对天然藻类和细菌组合的影响。这项工作将实验室和现场实验联系起来，以了解化学信号对海洋微生物相互作用的治理，并有可能对微生物相互作用如何影响海洋环境中的生物地球化学通量产生广泛适用的见解。

Bacteria and phytoplankton play a central role in the modification and flow of materials and nutrients through the marine environment. While it has been established that interactions between these two domains are complex, the mechanisms that underpin these interactions remain largely unknown. There is increasing recognition, however, that dissolved chemical cues govern these microbial interactions. This project focuses on establishing a mechanistic framework for how bacterially derived signaling molecules influence interactions between phytoplankton and bacteria. The quorum-sensing (QS) molecule, 2-heptyl-4-quinolone (HHQ) will be used as a model compound for these investigations. Previously published work suggests that exposure to very low levels of HHQ results in phytoplankton mortality. Gaining a mechanistic understanding of these ecologically important interactions will help to inform mathematical models for the accurate prediction of the cycling of material through the marine microbial loop. This work initiates a new, hybrid workshop-internship undergraduate research program in chemical ecology, with a focus into bacteria-phytoplankton interactions. Undergraduate students participate in an intense summer learning experience where research and field-based exercises are supplemented with short-lecture based modules. Students return to their home institutions and work closely with the PIs to conduct interdisciplinary research relating to the aims and scope of the summer research. This research also provides training and career development to two graduate students and a postdoctoral scientist.Interactions between phytoplankton and bacteria play a central role in mediating biogeochemical cycling and microbial trophic structure in the ocean. The intricate relationships between these two domains of life are mediated via excreted molecules that facilitate communication and determine competitive outcomes. Despite their predicted importance, identifying these released compounds has remained a challenge. The PIs recently identified a bacterial QS molecule, HHQ, produced by globally distributed marine gamma-proteobacteria, which induces phytoplankton mortality. The PIs therefore hypothesize that bacteria QS signals are critical drivers of phytoplankton population dynamics and, ultimately, biogeochemical fluxes. This project investigates the timing and magnitude of HHQ production, and the physiological and transcriptomic responses of susceptible phytoplankton species to HHQ exposure, and quantifies the influence of HHQ on natural algal and bacterial assemblages. The work connects laboratory and field-based experiments to understand the governance of chemical signaling on marine microbial interactions, and has the potential to yield broadly applicable insights into how microbial interactions influence biogeochemical fluxes in the marine environment.