Autoaggregation and adhesion abilities in bacteria associated with colonies of Microcystis

Bacteria associated with Microcystis may play an important role in formation of Microcystis colonies and in development of cyanobacterial blooms. Adhesion to Microcystis cells is a requirement for colonization and long-term association of bacteria with Microcystis colonies. This study aimed to explore the relationship between autoaggregation ability and adhesion ability of Microcystis -associated bacteria, and to evaluate the effects of different environmental factors on their autoaggregation abilities. Twelve bacterial strains were isolated from colonies of three Microcystis morphospecies. All the bacterial isolates exhibited autoaggregation abilities. A positive correlation was found between autoaggregation ability and adhesion ability. Two selected bacterial isolates, HJX5 and HJX9, exhibited strong autoaggregation abilities at pH from 3 to 11. The laboratory experiment revealed the inhibitory effects of metal cations on the autoaggregation abilities of HJX5 and HJX9, but HJX5 and HJX9 could exhibit their autoaggregation abilities in the lake water. Extraction of exopolysaccharides (EPS) decreased significantly their autoaggregation abilities, indicating that EPS can play an important role in autoaggregation. The autoaggregation ability of Microcystis -associated bacteria may be an important trait contributing to their attachment into Microcystis colonies.