Effect of two co-habitat bacteria on the recruitment of dormant Microcystis aeruginosa cells
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 10CT,strain H1)and one strain of algae-promoting bacterium(Bacillus zhangzhouensis DW5-4T,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/(m2·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 Hl 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.
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维普
