Abstract:

In the present study, culturable bacteria were isolated and purified from water samples of south Taihu Lake in four seasons by the dilution-plate method and modified isolation medium. These bacteria were identified using 16S rRNA gene sequence. Bacteria with algicidal activity against Microcystis aeruginosa were screened, and their active compounds were isolated and purified. It was shown that a total of 420 strains were isolated from water samples of south Taihu Lake in four seasons. They were classified into 192 species, 66 genera, 35 families, 20 orders, 9 classes and 4 phyla. Based on the isolated strain number, Flavobacterium, Pseudomonas, Brevundimonas and Bacillus were the majority at the genus level. There were 20 strains identified as potential new taxa by 16S rRNA gene sequence analysis. Seven strains showed obvious inhibitory activity against M. aeruginosa, of which Flavobacterium sp. 1-2-14 exhibited the strongest algicidal activity, as its inhibition rate reached 71.52% after co-cultured for 7 days. By adopting the tracing method of bioactivity, two compounds, cyclo (4-hydroxy-L-Pro-L-Leu) and pterodontriol B were isolated, and their inhibition rates against M. aeruginosa were 56.87%and 67.81% at 48 h, respectively.

Key words: south Taihu Lake, culturable bacteria, Microcystis aeruginosa, algicidal activity