Inorganic carbon and nitrogen assimilation in cellular compartments of a benthic kleptoplastic foraminifer
Inorganic carbon and nitrogen assimilation in cellular compartments of a benthic kleptoplastic foraminifer
复制标题
底栖盗塑有孔虫细胞室中的无机碳和氮同化
作者：
C. LeKieffre;Thierry Jauffrais;E. Geslin;B. Jesus;J. Bernhard;Maria;A. Meibom
德国Haynesina germanica是一种在潮间带泥滩中普遍存在的底栖有孔虫，具有从微藻中分离、隔离和利用叶绿体的显著能力。这些kleptoplasts的光合功能已被证明通过测量光系统II的量子效率和O2的生产率，但确切的作用kleptoplasts有孔虫代谢知之甚少。因此，C和N同化和转运的机制和动力学从kleptoplasts有孔虫宿主需要研究。本研究的目的是调查，使用相关的TEM和NanoSIMS成像，无机C和N（这里的铵，NH 4+）在一个kleptoplastic底栖有孔虫物种的个人同化。H.在光/暗循环期间，将德国藻标本在富含H13 CO 3 −和15 NH 4+的人工海水中孵育20 h。所有标本（n = 12）纳入13 C到他们的内质主要以脂滴的形式存储。在黑暗中的控制孵育导致没有13 C-吸收，强烈表明光合作用是主导无机C同化的过程。铵同化观察有和没有光，弥漫15 N-富集在整个细胞质和不同的15 N-热点纤维囊泡，电子不透明体，微管蛋白类晶体，细菌联营公司，很少和中等水平，在kleptoplasts。后一个观察结果可能表明，kleptoplasts参与N同化。然而，较高的N同化观察有孔虫内质孵育无光表明，另一种细胞质途径是占主导地位的，至少在黑暗中。这项研究清楚地表明了优势所提供的kleptoplasts作为一个额外的碳源，并提供了观察有孔虫细胞的铵吸收。
Haynesina germanica, an ubiquitous benthic foraminifer in intertidal mudflats, has the remarkable ability to isolate, sequester, and use chloroplasts from microalgae. The photosynthetic functionality of these kleptoplasts has been demonstrated by measuring photosystem II quantum efficiency and O2 production rates, but the precise role of the kleptoplasts in foraminiferal metabolism is poorly understood. Thus, the mechanism and dynamics of C and N assimilation and translocation from the kleptoplasts to the foraminiferal host requires study. The objective of this study was to investigate, using correlated TEM and NanoSIMS imaging, the assimilation of inorganic C and N (here ammonium, NH4+) in individuals of a kleptoplastic benthic foraminiferal species. H. germanica specimens were incubated for 20 h in artificial seawater enriched with H13CO3− and 15NH4+ during a light/dark cycle. All specimens (n = 12) incorporated 13C into their endoplasm stored primarily in the form of lipid droplets. A control incubation in darkness resulted in no 13C-uptake, strongly suggesting that photosynthesis is the process dominating inorganic C assimilation. Ammonium assimilation was observed both with and without light, with diffuse 15N-enrichment throughout the cytoplasm and distinct 15N-hotspots in fibrillar vesicles, electron-opaque bodies, tubulin paracrystals, bacterial associates, and, rarely and at moderate levels, in kleptoplasts. The latter observation might indicate that the kleptoplasts are involved in N assimilation. However, the higher N assimilation observed in the foraminiferal endoplasm incubated without light suggests that another cytoplasmic pathway is dominant, at least in darkness. This study clearly shows the advantage provided by the kleptoplasts as an additional source of carbon and provides observations of ammonium uptake by the foraminiferal cell.