初始密度对微小亚历山大藻生长及产麻痹性贝类毒素的影响

为研究微小亚历山大藻生长和产麻痹性贝类毒素(PSP)的规律,采用不同初始密度对微小亚历山大藻进行培养,综合采用显微镜计数、小鼠生物检测(MBA)、高效液相色谱—柱后衍生(HPLC-FLD)等方法分析微小亚历山大藻在不同接种密度条件下的生长和产毒特性.结果表明,随着初始密度增加微小亚历山大藻通过静止期的时间缩短,到达最大生长密度的时间提前,但是生长的最大细胞密度和平均比生长率却呈下降趋势,增值模型反应的情况与观测结果相一致,随着初始密度的增加,依赖于初始种群密度的参数(a)减少,环境容量(K)减少,种群瞬时增殖速度(r)下降.4种不同初始密度(0.05×104、0.10×104、0.15×104、0.30×104cells/mL)条件下,微小亚历山大藻细胞的毒性呈现先增大后减小趋势,在初始密度为0.1×104 cells/mL条件下,同一生长期内细胞毒性比其他3个密度条件下高.HPLC检测微小亚历山大藻含有的毒素为GTX1-4,含量分别为2.14、2.08、4.97、5.04 fmol/cell.综合考虑微小亚历山大藻在生长过程中的细胞最大密度、达到最大密度所用时间以及细胞毒性大小等因数,采用(0.10～0.15)×104 cells/mL接种密度培养微小亚历山大藻,能够达到较好的产毒效果.

Effects of different inoculation densities on growth and toxin production ofAlexandrium minutum

Effects of different inoculation densities on growth and toxin production of Alexandrium minutum were studied.Experiments were conducted under conditions of varying inoculation densities(0.05×10⁴,0.10×10⁴,0.15×10⁴,0.30×10⁴cells/mL).Higher inoculation densities always resulted in shorter lag phase of A.minutum,and an earlier setting in of the steady growth phase.However,the specific growth rate and maximum cell concentration of A.minutum decreased with increasing inoculation densities.The multiplication models developed correlated well with the observations,as the inoculation density increased,the initial-density dependent parameter a also deceased and the reduction of environmental capacity,instantaneous multiplication included.According to MBA analysis,toxicity of A.minutum is typically highest when cells are growing fast in early exponential phase and lowest as growth slows and eventually stops in plateau phase.The PSP-toxin congeners,GTX1(2.14 fmol/cell),GTX2(2.08 fmol/cell),GTX3(4.97 fmol/cell),GTX4(5.04 fmol/cell)were analysed by high-performance liquid chromatography with fluorescence diction(HPLC-FLD).Result of this study implied that toxin production of the dinoflagellate A.minutum is better in 0.10×10⁴-0.15×10⁴ cells/mL than other condition of inoculations densities.