Regulation of Photosynthesis During Nitrogen Fixation in a Filamentous Cyanobacterium (Biological Science)

大气中的氮还原为氨，称为固氮，被氧气抑制；因此，进化氧气的光系统II和固氮不能共存。一些丝状蓝藻，有光系统II，可以分化细胞，称为异囊，专门用于固氮。在异囊分化过程中发生了许多结构和生化变化，包括光系统II （PSII）活性的丧失。Thiel博士将研究异囊分化过程中该光系统成分失活的机制。她将在一个形成杂泡的蓝藻中通过Southern杂交鉴定PSII组分基因，通过Western blots鉴定PSII蛋白组分，并将研究这些基因的转录调控和这些蛋白在杂泡分化过程中的周转。这些研究应该提供有关细胞机制的信息，使具有氧进化PSII的生物体也能固定氮。Thiel博士将教授微生物学和生物能量学课程，在研究生研讨会课程中授课，并指导研究生的研究。她还将通过华盛顿大学妇女资源中心就妇女在科学领域的机会举行正式研讨会和非正式讨论。该项目进一步推进了VPW计划的目标，即(1)为女性提供在工程和NSF支持的科学学科中发展职业的机会；(2)通过为在工业、政府和学术机构工作的女性科学家和工程师提供更大的知名度，鼓励女性在科学和工程领域追求职业。通过鼓励妇女参与科学，这是对国家未来科学活力的宝贵投资。

The reduction of atmospheric nitrogen to ammonia, termed nitrogen fixation, is inhibited by oxygen; hence, oxygen-evolving photosystem II and nitrogen fixation cannot coexist. Some of the filamentous cyanobacteria, which have photosystem II, can differentiate cells, called heterocysts, that are specialized for nitrogen fixation. Many structural and biochemical changes occur during heterocyst differentiation, including loss of photosystem II (PSII) activity. Dr. Thiel will study the mechanism of inactivation of the components of this photosystem during heterocyst differentiation. She will identify in a heterocyst- forming cyanobacterium the genes for PSII components by Southern hybridization and the protein components of PSII by Western blots, and will study the regulation of transcription of these genes and the turnover of these proteins during heterocyst differentiation. These studies should provide information on the cellular mechanisms that allow an organism that has oxygen evolving PSII to also fix nitrogen. Dr. Thiel will team teach courses in Microbiology and in Bioenergetics, give lectures in graduate seminar courses, and direct the research of graduate students. She will also give formal seminars and have informal discussions on opportunities for women in science through the Women's Resource Center at Washington University. This project furthers VPW program objectives which are (1) to provide opportunities for women to advance their careers in engineering and in the disciplines of science supported by NSF and (2) to encourage women to pursue careers in science and engineering by providing greater visibility for women scientists and engineers employed in industry, government, and academic institutions. By encouraging the participation of women in science, it is a valuable investment in the Nation's future scientific vitality.