Microcystis and Anabaena are the main cyanobacteria that cause cyanobacterial blooms in Taihu Lake, China. The mechanism of population competition between M. aeruginosa and A. flos-aquae was studied by co-cultivation in the laboratory. The growth of M. aeruginosa was inhibited, while the growth of A. flos-aquae was promoted. The degree of inhibition or promotion was related to the ratio of the initial cell densities. Both cell-free filtrates of A. flos-aquae and co-culture inhibited M. aeruginosa growth, while both cell-free filtrates of M. aeruginosa and co-culture promoted A. flos-aquae growth. Analysis of the cell-free filtrate by gas chromatography-mass spectrometry indicated that M. aeruginosa and A. flos-aquae may secrete some extracellular allelochemicals that inhibit (promote) the growth of M. aeruginosa (A. flos-aquae) in co-culture. These compounds included sulfur compounds, naphthalene derivatives, cedrene derivatives, quinones, phenol derivatives, diphenyl derivatives, anthracene derivatives, and phthalate esters. This study can help to understand the characteristics of M. aeruginosa and A. flos-aquae and to provide new concepts for the control of cyanobacterial blooms in Taihu Lake.
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