Interactions of bacteria, viruses and bloom-forming diatom genus Pseudo-nitzschia

智力优势：本项目旨在阐明在沿海海洋环境中病毒、细菌和有毒藻华形成的海洋硅藻属伪尼茨奇亚之间的相互作用。世界性的伪nitzschia sp.（硅藻门）在世界各地引起有害的藻华。最近对两种海洋硅藻的基因组测序显示，细菌基因占其基因组组成的5%，突出了海洋硅藻与细菌在进化史上的密切联系。迄今为止，很少有人研究硅藻与其表面细菌之间的相互作用，也没有人采用直接实验的方法研究病毒、细菌和浮游植物之间的相互作用。本项目旨在研究藻类与微生物之间的生理、生化、遗传和生态相互作用，以揭示微生物对藻华动态和产毒的影响。本研究结合系统发育学、生理学、生物化学、比较基因组学和宏基因组学等方法，寻求以下问题的答案：1)与不同种类的假尼茨氏菌相关的附生细菌是什么？它们在不同的繁殖阶段是如何变化的？2)这些细菌如何影响伪尼茨氏菌宿主的生理，藻类宿主如何调节这些微生物的相互作用？3)病毒是否可以通过选择性地裂解灭藻细菌来促进水华，同时为促进生长的细菌创造机会，反之亦然？本项目以微生物-藻类相互作用的初步研究为指导，在该研究中发现两种伪尼茨氏菌存在明显不同的表观细菌群落。一种伪nitzschia sp的细菌同伴刺激了藻类宿主的生长，但在另一种伪nitzschia sp上作为病原体。本项目将通过采样更多的伪nitzschia物种，研究沿海海域伪nitzschia华爆发、高峰和衰退阶段后表观生物和浮游细菌群落结构的变化，扩大对表观生物细菌群落多样性和动态的研究。藻类寄主对表观生物关联的反应将采用二元和多元培养的生理实验方法进行研究。藻类宿主和表观细菌之间的化学交流将通过使用已建立的LC-MS和酶分析来观察藻类渗出分泌物和细菌酶分泌来解决。为了说明病毒对细菌-藻类相互作用的影响，我们将分离出表面生细菌特有的噬菌体并将其纳入生理实验。更广泛的影响：该项目将环境科学和工程教育与藻华期间微生物相互作用的深入研究结合起来。这一整合将通过培养少数民族博士后、扩大环境科学中代表性不足的群体的参与、让本科生尽早接触环境研究以及向社会推广来实现。招募和培训少数族裔研究参与者将与少数族裔科学计划（MSP）和加州少数族裔参与联盟（CAMP）计划合作进行。与暑期本科生研究项目（SURP）联合，将招收本科生在UCI学习的早期参与该项目。向社会和7 -12年级学生的推广将与由加州渔猎部管理的新港后湾科学中心合作完成。

Intellectual Merit: This project seeks to elucidate the interactions between viruses, bacteria and toxic bloom-forming marine diatom genus Pseudo-nitzschia in the coastal marine environment. The cosmopolitan Pseudo-nitzschia sp. (Bacillariophyceae) causes harmful algal blooms in various parts of the world. Recent genome sequences of two marine diatoms revealed that bacterial genes contribute up to 5% of their genome make-up, highlighting the close association of marine diatoms with bacteria in evolutionary history. So far, few have looked at the interactions of diatoms with their epibiotic bacteria and none have studied the interactions of virus, bacteria and phytoplankton using direct experimental approach. This project investigates the physiological, biochemical, genetic and ecological interactions of algae-microbe associations in order to decipher the influences of microbes on algal bloom dynamics and toxigenesis. By incorporating methods in phylogeny, physiology, biochemistry, comparative genomics and metagenomics, the research seeks answers to the following questions: 1) What are the epiphytic bacteria associating with different species of Pseudo-nitzschia and how do they change at different stages of the bloom? 2) How do these bacteria affect the physiology of the Pseudo- nitzschia hosts and how does the algal host regulate these microbial interactions? 3) Can viruses promote a bloom by selectively lysing algicidal bacteria, while creating opportunities for growth- promoting bacteria or vice versa? This project is guided by the preliminary research on microbe- algae interaction, where significantly different epibiotic bacterial communities were found to associate with two Pseudo-nitzschia species. Bacterial associates of one Pseudo-nitzschia sp. stimulated the growth of the algal-host but acted as a pathogen on another Pseudo-nitzschia sp. This project will expand the work on epibiotic bacterial community diversity and dynamics by sampling additional species of Pseudo-nitzschia and investigating the changes in epibiotic and planktonic bacterial community structure following the initiation, peak and decline phases of Pseudo-nitzschia blooms in coastal oceans. Algal host responses to epibionts association will be investigated using physiological experiments of binary and multi-culture experimental approaches. The chemical communication between algal host and epibiont bacteria will be addressed by looking at the algal exudate excretions and bacterial enzyme secretions using established LC-MS and enzyme assays. To illustrate the influences of viruses on bacterial-algal interaction, bacteriophages specific to epibiotic bacteria will be isolated and included in the physiological experiments.Broader Impacts: This project integrates education in environmental science and engineering with in-depth investigation of microbial interactions during algal bloom. The integration will be achieved through training of a minority postdoctoral fellow, broadening the participation of underrepresented groups in environmental science, early exposure of undergraduate students to environmental research, and outreach to society. The recruitment and training of minority participants in the research will be conducted in collaboration with Minority Science Program (MSP) and the California Alliance for Minority Participation (CAMP) program. Jointly with Summer Undergraduate Research Program (SURP), undergraduate students will be recruited to participate in this project at the early stage of their study in UCI. Outreach to society and 7th-12th grades students will be accomplished in collaboration with the Newport Back Bay Science Center managed by the California Department of Fish and Game.