Microcystis aeruginosa grown in different defined media leads to different cultivable heterotrophic bacteria composition that could influence cyanobacterial morphological characteristics and growth properties
Cyanobacterial blooms involving Microcystis spp. often pose severe problems to the environment and general community due to their persistent presence in eutrophic water bodies and potential to form blooms. Bacterial associations are known to alter microenvironment of Microcystis and potentially influence their development. This study aimed to study cultivable heterotrophic bacteria composition that developed symbiotically with Microcystis aeruginosa naturally as well as those cultured under defined media and their possible effects on the morphology and growth properties of the cyanobacterium. M. aeruginosa (UPMC-A0051) was isolated during a bloom from Putrajaya Lake, Malaysia and characterized as a non microcystin-producing cyanobacterium using PCR and chromatographic methods. Associated heterotrophic bacteria were then isolated and identified from the culture media as well as the lake where the cyanobacterium was originally isolated. A total of 16 bacterial species were isolated from the lake and none of them were similar to the bacteria associated with M. aeruginosa cultured in artificial media. Cultivable heterotrophic bacteria composition associated with M. aeruginosa were also distinct in different culture media, despite the same inoculum. These bacteria were classified under Actinobacteria, .-Proteobacteria and {beta}-Proteobacteria. Under different bacterial associations, M. aeruginosa cultivated in defined media showed different colony morphology and growth properties. The present study demonstrated that distinct bacterial composition observed in different culture media could be responsible for dissimilar cyanobacterium morphology and growth rate, particularly on the clustering pattern. In the axenic culture, the growth of M. aeruginosa was significantly reduced indicating the influence of associated bacteria on the development of cyanobacterial colonies.