小球藻两个品系在自养与异养条件下的生长、能荷与色素差异

Chlorella protothecoides中国品系(C品系)与美国品系(A品系)在自养培养基中生长正常。在高浓度葡萄糖、低浓度有机氮的异养生长条件下,C品系仍为绿色,细胞生长与繁殖缓慢,指数期生长速率降低,细胞内腺苷酸能荷值(AEC)下降,但细胞仍保留叶绿素;A品系细胞转变成乳黄色,细胞生长与繁殖加快,指数期生长速率是自养细胞的2倍,细胞内腺苷酸能荷值仍保持高水平,向异养条件转换后约24h,细胞内叶绿素基本消失,重新向自养条件转换后细胞内叶绿素又逐渐恢复。AEC值是判别微藻在异养条件下能量代谢与生理状态的良好指标。同一种小球藻不同品系间的上述差异可能与细胞内基因调控的差异相关联。

Growth, AEC and Pigments of Chlorella protothecoides in Two Strains Under the Autotrophic and Heterotrophic Conditions

Both Chinese strain(C strain) and American strain (A strain) of Chlorella protothecoides grew normally in autotrophic culture medium. They responded differently to heterotrophic conditions in the light. When incubated in heterotrophic medium with high Glu and low nitrogen concentration, cells of C strain remained green with chlorophyll, growth and reproduction turned slow with a low growth rate in the exponential growth phase and adenylate energy charge (AEC) in cells decreased obviously (Fig. 1,3, 4 and Table 1,2). Cells of A strain turned yellow with chlorophyll disappearing in heterotrophic medium (Fig. 2, 5). Their growth and reproduction became faster with a growth rate in the exponential growth phase 2 times that in autotrophic medium (Table 1). The AEC value of A strain remained at a high level (Fig. 3 and Table 2). Chlorophyll reappeared after the yellow cells were transferred back into autotrophic midium (Fig. 6,7). There are no remarkble changes in ratio between chlorophyll and carotene (A_(663)/A_(432)) in C strain in transferring process of culture conditions. But the speed of disappearance of chlorophyll in the transferring process of A strain from autotrophic culture to heterotrophic culture is lower than that of the reappearence of chlorophyll on the transferring process from heterotrophic culture to autotrophic culture.It is suggested that the value of AEC is a good index of physiology and energy metabolism in heterotrophic microalgae. The difference between the two strains of C. protothecoides under heterotrophic condition may be related to the differnce in gene-regulated adaptation in their cells.