[Effects of abiotic factors on algal extracellular polysaccharides content]

To get insight of the phenotypic variation mechanisms of Microcystis aeruginosa, this paper reviewed the research results on the effects of various abiotic factors on the content of algal extracellular polysaccharides. Many published papers demonstrated that there exists a definite responsive relationship between the content of algal extracellular polysaccharides and the ratios of main nutritive elements in the environment. Under the condition of high C:N or C:P ratio, i.e., under nitrogen or phosphorus deficiency, the organic substances fixed by the photosynthesis of algae are mainly existed in the forms of carbohydrates that do not contain nitrogen and phosphorus. The excessive accumulation of polysaccharides in algal cell induces their gradual release to the outside, resulting in a significant increase in the content of extracellular polysaccharides. Under the unbalanced condition of C or N metabolism, the extracellular polysaccharides can serve as a sink of excessively fixed carbon. For several kinds of algae, different light quality, light intensity and photoperiod can affect their synthesis and secretion of extracellular polysaccharides, and temperature can also affect the production of their extracellular polysaccharides to a certain extent. As the extracellular polysaccharides play a very important role in cementing cells together to form colonies, it's speculated that the increase of extracellular polysaccharides production by M. aeruginosa via the regulation of relevant abotic factors could be helpful to simultate the colony formation of M. aeruginosa in laboratory.