Hemoglobins in Mollusc/Bacteria Symbioses

软体动物/细菌共生中的血红蛋白

• 批准号: 8703328
• 负责人: Jonathan Wittenberg
• 金额: --
• 依托单位: Yeshiva University, Albert Einstein College of Medicine
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 1987
• 资助国家: 美国
• 起止时间: 1987-07-01 至 1989-12-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=8703328&HistoricalAwards=false
• 关键词: Hemoglobins; Mollusc; Bacteria; Symbioses

Clams and mussels living in environments where hydrogen sulfide and oxygen coexist in disequilibrium frequently lack (or essentially lack) both mouth and guts and rely for their carbon nutrition on symbiotic bacteria housed in the modified gill. The bacteria derive energy by oxidizing hydrogen sulfide and fixing carbon dioxide into organic compounds which serve as food for the clam. The prototype of these symbiont-dependent animals is the giant white clam collected by the deep submersible Alvin, from the Galapagos hydrothermal vents on the floor of the Pacific Ocean. Similar but accessible species living in the mud of mangrove swamps are being studied in this project. Specialized cells (bacteriocytes) in the gills of these clams house the symbiotic bacteria and also contain hemoglobin at great concentration. It is being determined how the hemoglobin carries both oxygen and hydrogen sulfide from the sea water across the cytoplasm of the cell to the symbiotic bacteria. The primary aim is to reconstruct the molecular mechanism of hemoglobin-mediated oxygen delivery to the intracellular symbiont. It is proposed that the same molecular mechanism which delivers oxygen to bacteria in the clam gill serves also in the economically important root modules of soybeans and other legumes, and in the human heart. In the soybean root nodule, leghemoglobin delivers oxygen to intracelluar bacteria, Rhizobium, which fix nitrogen from the atmosphere and supply it the plant. These plants do not require nitrogen fertilizer. Myglobin in the human heart delivers oxygen to intracellular mitochondria, enabling them to make ATP, the fuel of muscle contraction, rapidly enough to meet the work load of the heart.

生活在硫化氢和氧气不平衡共存的环境中的文蛤和贻贝经常缺乏(或基本上缺乏)口腔和肠道，它们的碳营养依赖于寄生在改良鳃中的共生细菌。细菌通过氧化硫化氢和将二氧化碳固定为有机化合物来获取能量，这些有机化合物可以作为贻贝的食物。这些依赖共生生物的动物的原型是阿尔文号深海潜水器从太平洋海底加拉帕戈斯热液喷口收集的巨大白色文蛤。该项目正在研究生活在红树林沼泽淤泥中的类似但可接近的物种。这些文蛤鳃中的特化细胞(细菌体)容纳着共生菌，也含有大量的血红蛋白。人们正在确定血红蛋白如何将氧气和硫化氢从海水中穿过细胞质运送到共生细菌。其主要目的是重建血红蛋白介导的向细胞内共生体输送氧气的分子机制。有人提出，将氧气输送到文蛤鳃中细菌的分子机制也适用于大豆和其他豆类的经济重要的根模块，以及人类的心脏。在大豆根瘤中，豆类血红蛋白向细胞内细菌根瘤输送氧气，根瘤菌从大气中固定氮并将其供应给植物。这些植物不需要氮肥。人类心脏中的肌红蛋白向细胞内线粒体输送氧气，使他们能够足够快地制造ATP，肌肉收缩的燃料，以满足心脏的工作负荷。