无机碳与雨生红球藻(Haematococcus pluvialis)细胞调节物质

以单细胞雨生红球藻为材料，采用酸碱滴定和CO2加富通气培养微藻的方法，对旧液中HCO3^-和CO3^2-浓度变化以及对红球藻细胞生长的影响进行了研究。结果表明，旧液具有限制红球藻细胞生长和诱导细胞转化的作用。同时，旧液中无机碳离子浓度明显高于新液。培养液中富含CO3^2-时，各细胞数量与CO3^2-浓度呈正相关，相关系数为0．88。溶液中仅有HCO3^-时，各细胞数与HCO3^-浓度也呈正相关性。因此，排除了CO3^2-和HCO3^-作为旧液中的调节物质，限制红球藻细胞生长和诱导细胞转化的可能性。旧液乙酸乙酯提取物生物检测实验表明，在粗提取物中有降低细胞增长和诱导细胞转化的活性，表明调节物质能溶于有机相，也反过来证实无机碳离子不是旧液中的调节物质。DNA含量和倍性分析结果表明，红球藻游动细胞DNA复制可以加倍后不经过原生质分裂就可以再次进行，因此推测旧液中的调节物质对原生质分裂过程产生抑制作用，而不对DNA复制过程产生抑制作用。

INORGANIC CARBON AND THE CELL GROWTH REGULATOR IN MICRO-ALGA HAEMATOCOCCUS PLUVIALIS

Auto-regulation, probably a common phenomenon in micro-algae cultivation has been long overlooked in the low-cell-density cultures, especially at early culture stages because of the low auto-regulator concentration. In high-cell-density culture, however, auto-regulation become an important issue and occurs heavily at the later culture stages. To date, scientists are unsure exactly what kind of substance the auto-regulator is. Our early data has revealed an unknown bioactive substance produced by Haematococcus cell that feedback influences cell growth and transformation and effectively regulates cell cycles. About 60 years ago, Pratt (1942, 1944) and Pratt et al (1940, 1945) showed some auto-produced signal substances termed chlorellin feedback regulating Chlorella cell growth. Mandalam et al (1995)considered autoinhibitor does not exist in the old culture, and it is inorganic carbons play the inhibitory role on Chlorella growth. In this study, the relationship of HCO₃^- or CO₃^-2 to cell growth and cell transformation of H.pluvialis in static, aerated and/or CO₂-enriched aerated culture was investigated comparatively in Qingdao from 1999 to 2002 using a fresh medium and an old culture supernatant with equal content of nutrients. Results of CO₂-enriched aerated culture showed that motile cell growth rate in Haematococcus old culture was reduced, meanwhile cell transformation from motile cells to non-motile cells accelerated. These results imply that some unknown substances, such as an auto-regulator, existed in the old culture blocking Haematococcus motile cell division and inducing the process of cell transformation. Although CO₃^-2 and HCO₃^- concentration in supernatant of Haematococcus old culture was similar to that in Chlorella old culture supernatant, and the growth rate of motile cells in the old culture was significantly affected (much lower than that of flesh medium), further studies did not support a positive connection between inorganic carbons (CO₃^-2 or HCO₃^-) and the auto-regulator. On the contrary, inorganic carbons promoted motile cell growth rates in some aspects. In addition, crude ethyl acetate extracts from the old culture supernatant also showed similar bioactivity i.e. inhibiting motile cell growth and promoting cell transformation from motile cells to non-motile cells. Therefore, auto-regulators in Haematococcus old culture supernatant, unlike inorganic substance, are organic dissoluble substances. Our DNA data and histogram of motile cells also showed that the process of DNA replication in the motile cells did not stop, but the process of the plasm division was heavily blocked by the old culture supernatant. Although no evidence indicated that inorganic substances were the respected auto-inhibitors, however, from the auto. inhibitors point of view, some obscure issues (for example, the reason why Haematococcus culture was hardly kept as stable as other microalgae, why Haematococcus suddenly grew fast after inoculation even in distill water, why Haematococcus can only be found as dominant specie in shallow water pools on the rocks after raining in nature) were easily understood.