氮磷对铜绿微囊藻群体形态的影响

在自然条件下,铜绿微囊藻主要以群体形态存在,其群体形态通常由10~103数量级的单位细胞组成,然而在实验室条件下经过几代培养之后,铜绿微囊藻的群体形态逐渐变为单细胞和少量双细胞. 在实验室条件〔温度为(25±1)℃,光照强度为2 000 lx,光暗比为12 h∶12 h〕下,采用不同ρ(TN)、ρ(TP)的BG11培养基培养群体形态的太湖铜绿微囊藻(FACHB912),其中T1试验组ρ(TN)、ρ(TP)分别为1.00、0.05 mg/L,T2试验组为5.00、0.25 mg/L,T3试验组为25.00、1.25 mg/L,T4试验组为125.00、6.25 mg/L,T5试验组为247.06、7.11 mg/L. 结果表明:T1、T2和T3试验组铜绿微囊藻群体形态细胞所占比例及群体大小均有所增加,T4和T5试验组则表现为减少,并且T1、T2、T3试验组与T4、T5试验组间差异显著(P<0.05). T1、T2、T3试验组出现了>100个细胞的群体,其中T2试验组的铜绿微囊藻群体最大,最大群体约由960个藻细胞组成；而T4、T5试验组中的群体却趋于消失. 相对于单细胞,群体形态的铜绿微囊藻在低ρ(TN)、ρ(TP)条件下能吸收更多的营养盐,有利于细胞的生长；高ρ(TN)、ρ(TP)条件下提供了丰富的营养盐,但可能抑制或者不能刺激胞外多糖的合成和分泌,从而不利于铜绿微囊藻群体形态的维持. 

Effects of Nitrogen and Phosporous on Colony Formation of Microcystis aeruginosa

It is widely recognized that a colony of Microcystis with several hundreds or even thousands of cells in a field will be replaced by a single cell and a few paired cells after several generations in axenic laboratory cultures. Microcystis aeruginosa were collected from Lake Taihu to conduct a laboratory experiment ((25±1)℃, 2000 lx, 12 h∶12 h) with different levels of ρ(TN) and ρ(TP) of blue-green medium (BG11). The ρ(TN) and ρ(TP) of T1, T2, T3, T4, T5 were 1.00 and 0.05 mg/L, 5.00 and 0.25 mg/L, 25.00 and 1.25 mg/L, 125.00 and 6.25 mg/L, 247.06 and 7.11 mg/L (BG11), respectively. During the experiment, the colony size and the proportion of cells in colonial form of M. aeruginosa increased in T1, T2, and T3, but decreased in T4 and T5. A significant difference was found between the treatments of T1, T2 and T3 and the treatments of T4 and T5 (P<0.05). Colony sizes over than 100 cells were observed in T1, T2, and T3. The colony developed best in T2 and the largest colony was about 960 cells per colony. In contrast, colony formation was entirely absent in T4 and T5. The colony formation of M. aeruginosa absorbed more nutrients and had higher cell growth in low ρ(TN) and ρ(TP). However, high ρ(TN) and ρ(TP) that provide a wealth of nutrients may inhibit or not stimulate the synthesis and secretion of extracellular polysaccharides of M. aeruginosa cells, and this is a disadvantage to colony formation maintainance.