Oxygen and Sulfide Delivery to Intracellular Bacterial Symbionts

几乎所有双壳类和腹足类软体动物的细胞质血红蛋白特征，其中趋化自养细菌作为内部共生体存在，对共生关系至关重要。从蛤蚌Lucina的鳃中分离出三种这样的血红蛋白，并测定了它们与硫化物或氧的相互作用。这些血红蛋白在共生关联中的作用现在将使用含有共生细菌、纯化的鳃血红蛋白、硫化物和氧气的破细胞系统来检查。研究细胞质血红蛋白介导的细菌共生体的氧传递和硫化物传递的分子机制；血红素或配体的还原对配体解离的影响将被检查。通过这些研究，我们对细菌利用硫化物氧化获得的能量利用二氧化碳的方法的理解应该得到加强，从而支持这种蛤蜊和其他类似的微生物的生命。血红蛋白存在于海洋无脊椎动物细胞质中的特殊作用和机制，其中存在一种涉及内化自养细菌的不寻常的共生关系，将根据无脊椎动物血红蛋白向细菌运输氧气和硫化物的能力进行研究。微观生物和宏观生物的这种相互依存关系越来越被人们所认识；对无脊椎动物有毒的硫化物到达共生体并保护其不受氧气影响的方法的理解应该通过这项研究得到扩大。//

Cytoplasmic hemoglobins characteristic of nearly all bivalves and gastropod molluscs in which chemoautotrophic bacteria are present as internal symbionts appear vital to the symbiosis. Three such hemoglobins, from gills of the clam Lucina, have been isolated and their interactions with either sulfide or oxygen determined. The role(s) of these hemoglobins in the symbiotic association will now be examined using broken-cell systems containing symbiotic bacteria, kpurified gill hemoglobins, sulfide, and oxygen. The molecular mechanisms of cytoplasmic hemoglobin-mediated oxygen delivery and sulfide delivery to the bacterial symbionts will be studied; the effects of reduction of either heme or the ligand on ligand dissociation will be examined. Our understanding of the means whereby the bacteria utilize carbon dioxide using energy gained from sulfide oxidation, thus supporting life of this clam and other similar macrobes should be enhanced by these studies. The particular roles and mechanisms whereby hemoglobins, present in the cytoplasm of certain marine invertebrates in which an unusual symbiosis involving internalized chemoautotrophic bacteria exists, will be studied in terms of the ability of the invertebrate's hemoglobins to transport oxygen and sulfide to the bacteria. This inter-dependence of micro- and the macro-organism is an increasingly recognized one; an understanding of the means whereby sulfide, toxic to the invertebrate, reaches the symbiont and is protected from oxygen should be enlarged by this study. //