中肋骨条藻与锥状斯氏藻藻际细菌溶藻效应研究

通过向对数生长期的中肋骨条藻和锥状斯氏藻培养体系中分别加入体积分数1%和10%的2216E培养基,以未加入培养基的对照组和10%无菌组作为对照,研究藻际细菌的溶藻效应.结果表明,对照组、1%组及10%无菌组的中肋骨条藻和锥状斯氏藻生长未受抑制,而10%组的中肋骨条藻和锥状斯氏藻生长则受到显著的抑制(p0.001),在第96h时,藻细胞几乎都被裂解,藻细胞数、叶绿素a含量及叶绿素荧光效率(Fv/Fm)显著低于对照组、1%组及10%无菌组(p0.001),表明藻际细菌具有抑制微藻生长的作用.在整个溶藻过程中,中肋骨条藻10%组细菌丰度增加了约250倍,锥状斯氏藻10%组藻际细菌丰度增加了约300倍,藻际细菌丰度的剧增可能是溶藻的主要原因.作为溶藻效果的评价指标,叶绿素荧光效率要优于细胞形态的改变、藻细胞数量的变化及叶绿素a含量,是较理想的溶藻检验指标.

The lytic effect of bacteria in the phycosphere of Skeletonema costatum and Scrippsiella trochoidea

The lytic effect of bacteria on cultured microalgae, Skeletonema costatum and Scrippsiella trochoidea, was studied by adding 1% (v/v) and 10% (v/v) of the bacteria culture medium 2216E to cultures of the two red tide microalgae. Microalgal cultures without addition of 2216E medium were used as the first negative controls, while the axenic microalgal cultures (obtained by antibiotic treatment) with additions of 10% (v/v) of 2216E medium were used as the second negative controls. The results showed that the growth of both microalgae in the treatments with 1% bacteria medium added was not statistically different from that in the negative controls. In contrast, the growth of both microalgae with 10% bacteria medium added was dramatically inhibited (p<0.001). At 96 h, most of the algal cells were lysed and very low levels of algal cell density, chlorophyll-a concentration, and variable chlorophyll fluorescence (Fv/Fm) were detected (p<0.001). Meanwhile, the bacterial abundance in the two microalgal cultures increased about 250~300 times following the algal lysis, which suggested a cause-effect relationship between the bacterial abundance and the dissolution of algal cells. Comparing the four indexes used to evaluate the lytic effect, Fv/Fm appeared to be the best index over the cell morphological change, algal cell density, and chlorophyll-a concentration. These results suggested that natural bacteria in the phycosphere might play an important role in regulating the growth of microalgae in the field.