Changes in extracellular polysaccharide content and morphology of Microcystis aeruginosa at different specific growth rates
- 972 Downloads
The cyanobacterium Microcystis mainly exists in colonies under natural conditions but as single cells in typical laboratory cultures. Understanding the mechanism by which single cells form small and large colonies can provide a deeper insight into the life history of Microcystis and the mechanisms of Microcystis bloom formation. In this paper, Microcystis aeruginosa cultured under varying light intensities and temperatures exhibited different specific growth rates. Correlations were found between the specific growth rate, extracellular polysaccharide (EPS) content, and morphology of M. aeruginosa. Under low light intensities and temperatures, M. aeruginosa formed small colonies (maximum colony size approximately 100 μm) and exhibited low specific growth rates. By contrast, standard culture conditions yielded single or paired cells with high specific growth rates. Moreover, the EPS content decreased dramatically with increasing specific growth rate. A significant positive linear relationship was observed between the EPS content per cell and colony size. High EPS content and colony formation were associated with low specific growth rates. The specific growth rate in laboratory cultures was higher than the in situ growth rate under natural conditions. This result may explain why Microcystis normally exists as single cells or (more rarely) as paired cells in axenic laboratory cultures after long-term cultivation, but forms colonies under natural conditions.
KeywordsMicrocystis aeruginosa Light intensity Temperature Specific growth rate EPS Morphology
We thank two anonymous referees for carefully reviewing the manuscript and for their constructive comments which improved it substantially. This study was sponsored by the National Program on Key Basic Research Project of China (2012CB719804), the Natural Science Foundation of Jiangsu Province (BK2011025), and the Hydraulic Science & Technology Project of Jiangsu Province (2011069).
- Downing TG, Sember CS, Gehringer MM, Leukes W (2005) Medium N: P ratios and specific growth rate comodulate microcystin and protein content in Microcystis aeruginosa PCC7806 and M. aeruginosa UV027. Microb Ecol 49:468–473Google Scholar
- Langdon C (1993) The significance of respiration in production measurements based on oxygen. ICES Mar Sci Symp 197:69–78Google Scholar
- Pereira S, Zille A, Micheletti E, Moradas-Ferreira P, De Philippis R, Tamagnini P (2009) Complexity of cyanobacterial exopolysaccharides: composition, structures, inducing factors and putative genes involved in their biosynthesis and assembly. FEMS Microbiol Rev 33:917–941PubMedCrossRefGoogle Scholar
- Plude JL, Parker DL, Schommer OJ, Timmerman RJ, Hagstrom SA, Joers JM, Hnasko R (1991) Chemical characterization of polysaccharide from the slime layer of the cyanobacterium Microcystis flos-aquae C3-40. Appl Environ Microb 57:1696–1700Google Scholar
- Reynolds CS, Jaworski GHM, Cmiech HA, Leedale GF (1981) On the annual cycle of the blue-green alga Microcystis aeruginosa Kütz. emend Elenkin Phil Trans R Soc B 293:419–477Google Scholar
- Watanabe MF, Oishi S (1985) Effects of environmental factors on toxicity of a cyanobacterium (Microcystis aeruginosa) under culture conditions. Appl Environ Microb 49:1342–1344Google Scholar
- Wu X, Kong F (2008) The determination of in situ growth rates of the bloomed Microcystis in Meiliang Bay, Lake Taihu (in Chinese). China Env Sci 28:552–555Google Scholar