The Role of Bacterial Symbionts of Marine Sponges in Nitrogen Fixation

海绵是复杂微生物群落的宿主，微生物群落可能占海绵生物量的60%。关于这些共生细菌的作用以及它们对海绵的贡献，从而间接地对海绵所在的珊瑚礁生态系统的贡献，人们知之甚少。推动该项目的假设是，不同的固氮菌组合在为海绵提供氮、吸收氮气并将其转化为可供海绵使用的有机形式氮的过程中发挥着重要作用。来自佛罗里达州Key Largo、Ircinia strobilina和Mycale laxissima的两种海绵的细菌共生体在固氮中的作用将被确定。该项目将包括展示整个海绵和细菌分离株固氮的生物化学方法，以及研究nifH基因何时何地启动并使nifH蛋白成为固氮关键蛋白质的分子方法。将为研究生提供海洋微生物学培训，鼓励本科少数民族学生通过参加海洋微生物学暑期课程进入科学研究生涯。该项目将促进我们对复杂海绵共生体中微生物多样性和功能的理解，促进海绵共生体作为微生物与许多高等生物之间复杂共生关系的模型的研究。该项目将为脆弱的珊瑚礁环境提供有关氮源的新信息。

Marine sponges are hosts to complex microbial communities that may comprise up to 60% of the sponge biomass. Little is known about the roles of these symbiotic bacteria and their contributions to the sponge and thereby indirectly to the coral reef ecosystem in which the sponges live. The hypothesis driving the project is that diverse assemblages of nitrogen-fixing bacteria play an important role in providing sponges with nitrogen, taking nitrogen gas and converting it to organic forms of nitrogen that can be used by sponges. The role of bacterial symbionts of two sponges from Key Largo, Florida, Ircinia strobilina and Mycale laxissima in nitrogen fixation will be determined. The project will include biochemical approaches to demonstrate nitrogen fixation in whole sponges and bacterial isolates, and molecular approaches to study the pattern of where and when the nifH gene is turned on and makes the NifH protein, a key protein in nitrogen fixation. Training will be provided in marine microbiology to graduate students and undergraduate minority students will be encouraged to enter careers in scientific research by participating in a summer course in Marine Microbiology. The project will advance our understanding of microbial diversity and function in complex sponge symbioses, promoting the study of sponge symbioses as models of the complex symbiotic relationships found between microbes and many higher organisms. The project will provide new information on sources of nitrogen for fragile coral reef environments.