发状念珠藻单体细胞混合营养模式下光合自养和异养代谢的关系

Interactions between Autotrophic and Heterotrophic Metabolism in Mixotrophic Cultures of Nostoc flagelliforme Cells

采用摇瓶培养研究了发状念珠藻单体细胞混合营养模式下光合自养和异养代谢的关系。结果表明在混合营养模式和光合自养模式中,发状念珠藻单体细胞的生长和胞外多糖的累积均随着光照强度的增加而增加。添加50μmol·L-1的光合抑制剂DCMU可以完全抑制发状念珠藻单体细胞的光合自养生长。发状念珠藻单体细胞混合营养模式中细胞的光合自养和异养代谢具有交互作用。在光照强度低于20μmol photon·m·2·s-1时,发状念珠藻单体细胞的混合营养生长中以异养生长为主,即主要是葡萄糖代谢作用提供细胞混合营养生长的能量,与光合自养和异养模式相比,细胞的光合自养和异养代谢均受到抑制。当光照强度高于20μmol photon·m·2·s-1时,在实验范围内随着光照强度的提高,混合营养模式下光合自养代谢得到促进,即葡萄糖的添加促进了发状念珠藻单体细胞的光合作用,与光合自养和异养模式相比,光合自养代谢得到促进,而异养代谢受到抑制。

The interactions between autotrophic and heterotrophic metabolism in mixotrophic cultures of Nostoc flagelliforme cells were studied.The results show that the cell growth and the accumulation of exopolysaccharides（EPS） increase prominently with the increase of the light intensity in both mixotrophic and autotrophic culture modes.It was also found that,in the mixotrophic culture mode,the photoautotrophic and heterotrophic metabolic activities process concurrently and dependently;and the growth of N.flagelliforme cells by autotrophic cultures can be inhibited completely by adding the inhibitor of photosynthetic electron transport DCMU with its amount of 50 μmol·L-1.Under lower light intensity（less than 20 μmol photon·m·2·s-1）,the heterotrophic growth is dominative in mixotrophic culture,that is,the metabolic activity of glucose supplies the energy for the cell growth of the mixotrophic culture.However,compared with the pure heterotrophic cultures or autotrophic cultures under the same other experimental conditions,the heterotrophic and autotrophic metabolic activities are inhibited.When the light intensity is increased（higher than 20μmol photon·m·2·s-1）,the autotrophic growth is enhanced,that is,the addition of glucose promotes the photosynthesis of N.flagelliforme cells in mixotrophic cultures.Compared with the pure heterotrophic cultures or autotrophic cultures within the range of experiments,in the mixotrophic cultures with addition of glucose,the heterotrophic growth is inhibited,while the autotrophic growth is increased.