蛋白核小球藻生长和无机碳利用对不同光照强度和CO2浓度的响应

为了探讨光照强度和CO₂浓度对蛋白核小球藻(Chlorella pyrenoidosa)生长、无机碳利用的复合效应, 丰富绿藻中无机碳浓缩机制的资料, 该文设置两种光照强度(40和120 µmol photons?m^-2?s^-1)和两种CO₂浓度(0.04%和0.16%)组合成4种条件, 比较了蛋白核小球藻生长、无机碳浓度、pH补偿点、光合放氧速率、碳酸酐酶(CA)活性和α-CA基因转录表达对这4种培养条件的响应。结果发现: 蛋白核小球藻在高光强高CO₂浓度组生长最快; 低光强高CO₂浓度组培养体系中总无机碳浓度为1163.3 µmol?L^-1, 显著高于其他3组; 高光强低CO₂浓度组藻的pH补偿点最高(9.8), 而低光强高CO₂浓度组藻的pH补偿点最低(8.6); 低光强高CO₂浓度组藻的最大光合速率(V_max)和最大光合速率一半时的无机碳浓度(K_0.5)最高, 分别是其他3组的1.28-1.91倍和1.61-2.00倍; 高光强低CO₂浓度组藻的胞外CA活性最高; 而低光强低CO₂浓度组藻的胞外α-CA基因表达量显著高于其他3组。以上结果表明低CO₂浓度可促进蛋白核小球藻的pH补偿点和无机碳亲和力的提高, 诱导胞外CA活性及α-CA基因的表达; 该藻主要以HCO₃^-为无机碳源, 其对无机碳的利用受光照的调节。

Response of growth and inorganic carbon utilization to different light and CO2 levels in Chlorella pyrenoidosa

AimsCarbon concentrating mechanism (CCM) is one of the important contents in algal physiology and ecology. Numerous studies have been carried out in eukaryotic and prokaryotic algae, but the information on economic microalga Chlorella pyrenoidosa (Chlorophyta) is limited. Our purpose is to explore the composite effect of light and CO₂ on growth, inorganic carbon utilization in C. pyrenoidosa, and enrich the data on CCM in green algae.
Methods Two light intensities (40 and 120 µmol photons?m^-2?s^-1) and two CO₂ concentrations (0.04% and 0.16%) were combined into four treatments, and then the algal growth, inorganic carbon concentration, pH compensation point, photosynthetic oxygen evolution rate, carbonic anhydrase (CA) activity and α-CA gene expression were investigated.
Important findings Chlorella pyrenoidosa grew fastest under the high-light and high-CO₂ condition. The total inorganic carbon concentration under low-light and high-CO₂ group was 1163.3 µmol·L^-1, which was significantly higher than that of other three groups. The alga had the maximal pH compensation point of 9.8 under the high-light and low-CO₂ condition, and the minimal pH compensation point of 8.6 under the low-light and high-CO₂ condition. The maximum photosynthetic rate (V_max) and inorganic carbon concentration in half maximum photosynthetic rate (K_0.5) in the low-light and high-CO₂ group were the highest, which were 1.28-1.91 times and 1.61-2.00 times of that in other three groups, respectively. The highest activity of extracellular CA was detected in the high-light and lower-CO₂ group. However, α-CA gene expression reached the maximum under the low-light and low-CO₂ condition. The results indicated that the low CO₂ level could increase the algal pH compensation point, photosynthetic inorganic carbon affinity, and induce the external CA activity and α-CA gene expression in C. pyrenoidosa. HCO₃^- was used as the primary inorganic carbon source, and the inorganic carbon utilization was also regulated by light in C. pyrenoidosa.