2株共栖菌对铜绿微囊藻休眠体复苏的影响

Effect of two co-habitat bacteria on the recruitment of dormant Microcystis aeruginosa cells

为探讨水生共栖菌H1(Sphingobacterium kitahiroshimense 10C^(T))与H2(Bacillus zhangzhouensis DW5-4^(T))对铜绿微囊藻休眠体(DMCs)复苏的联合作用,将菌株H1、H2按不同菌浓度比(菌比)与DMCs用沉积物混匀包埋,以无菌组为对照,在温度15和25℃、光照强度15μmol/(m^(2)⋅s)和光暗比10h:14h条件下进行室内复苏实验,并结合室内实验结果开展野外实验.实验结果表明,低菌比(≤3)时,菌组DMCs可溶性胞外多糖(SPS)浓度显著下降,固着性胞外多糖(CPS)与DMCs光合效率(Fv/Fm)无显著变化(P>0.05),SPS下降不影响Fv/Fm,菌群通过泌出3种代谢产物显著提升DMCs复苏率.菌比提高(≥5)时,菌组DMCs的SPS和CPS浓度均显著下降,其Fv/Fm也显著下降(P<0.05),CPS浓度下降抑制了DMCs光合效率,高菌比菌群通过降低DMCs的光合效率和泌出2种有效抑制DMCs复苏的代谢产物协同降低DMCs复苏率(纯代谢产物作用下的DMCs复苏率高于同条件下菌组复苏率).野外定性实验证实了菌比显著影响DMCs复苏率,实验结果为进一步利用微生物制剂抑控DMCs复苏提供理论依据.

Both benthic bacteria and dormant M.aeruginosa cells(DMCs)are important members of aquatic ecosystems.In our previous research work,one strain of algae-inhibiting bacterium(Sphingobacterium kitahiroshimense 10C^(T),strain H1)and one strain of algae-promoting bacterium(Bacillus zhangzhouensis DW5-4^(T),strain H2)were isolated simultaneously from the same aquaculture fishpond.Recruitment experiments were conducted to unveil the combined impact of the two bacteria on the DMCs recruitment.Strain H1 and H2 at different bacterial ratios were mixed with DMCs and embedded into sediments.The experiments were conducted at temperature 15℃and 25℃,a photoperiod of 12h light:12h dark,and a light intensity of 15μmol/(m^(2)⋅s)for 21 d.The results showed that when the bacterial ratio was less than three,the concentration of soluble extracellular polysaccharides(SPS)of DMCs in bacterial groups significantly reduced compared with the control group(sterile group),while there was no significant difference in capsular extracellular polysaccharides(CPS)and photosynthetic efficiency(Fv/Fm)of DMCs(P>0.05).The SPS concentration decrease did not affect Fv/Fm,and the strains H1 and H2 significantly improved the recruitment rate of DMCs by secreting three metabolites.When the bacterial ratio was greater than five,the SPS,CPS,and Fv/Fm in the bacterial groups were significantly lower compared with the control group(P<0.05).The decrease of CPS concentration inhibited the photosynthetic efficiency(Fv/Fm)of DMCs,and under high bacterial ratio condition the strains H1 and H2 synergistically reduced the recruitment rate of DMCs by reducing the photosynthetic efficiency(Fv/Fm)of DMCs and secreting two metabolites that effectively inhibited DMCs recruitment(the recruitment rate of DMCs under pure metabolite was higher than that of the bacterial groups).Interestingly,field qualitative experiments confirmed that the different bacterial ratio of strains H1 and H2 significantly affects the recruitment rate of DMCs,and the experimental results provide new ideas for predicting the recruitment rate of DMCs in early spring and a new approach for early preventing formation of M.aeruginosa blooms.