THE PARTITION PATTERN OF GLYCOGEN AND EXTRACELLULAR POLYSACCHARIDES IN TWO FILAMENTOUS CYANOBACTERIA FROM DESERT SOIL CRUSTS

Cyanobacteria often store excessive organic carbon in the form of glycogen and extracellular polysaccharides (EPS) under higher light intensities. However, their partition pattern and relation has long been overlooked. In this study, the partition and possible relationship between extracellular EPS and intracellular glycogen under different light intensities (4, 40, 80 mu E m(-2)s(-1)) were explored; with the exception of glycogen and EPS, the intracellular total sugar, water soluble sugar and sucrose of two species cyanobacteria, Microcoleus vaginatus FACHB 896 and Nostoc sp. FACHB 892 isolated from biological soil crusts, were also synchronously analyzed. The results showed that, the production of EPS (including released polysaccharides, RPS and capsular polysaccharides, CPS) in the two species all began from the exponential phase, and increased with the increasing light intensities, but glycogen content did not increase until the increment of light intensities was enough strong. Even though, their competition was obvious at the optimal light intensity. In pattern, even at the exponential phase, the two species only partitioned a little organic carbon in glycogen, more than 10 times in EPS. In EPS, CPS generally accounted for higher proportion than RPS, but the increase of RPS was much higher than that of CPS with the increasing light intensity and culture time. These results suggested that the partition of extracellular EPS and intracellular glycogen was closely related to acclimation to light intensity.