Effects of growth condition on the structure of glycogen produced in cyanobacterium Synechocystis sp. PCC6803.
Growth and glycogen production were characterized for Synechocystis sp. strain PCC6803 grown under continuous fluorescent light in four variations of BG-11 medium: either with (G+) or without (G-) 5mM glucose, and with a normal (N+, 1.5 g sodium nitrate/L) or a reduced (N-, 0.084 g sodium nitrate/L) nitrogen concentration. Glucose-supplemented BG-11 with a normal nitrogen concentration (N+G+) produced the highest growth rate and the greatest cell density. Although the maximum cell mass production was observed in the N+G+ medium, the highest glycogen yield (19.0mg/g wet cell mass) was achieved under the glucose-supplemented, nitrogen-limiting condition (N-G+). The addition of glucose enhanced cell growth, while nitrogen limitation apparently directed carbon flux into glycogen accumulation rather than cell growth. Transmission electron microscopic analysis showed that, under nitrogen-limiting conditions (N-G+), glycogen particles accumulated in large amounts and filled the cytosol of the cells. Analysis by high-performance size-exclusion chromatography further revealed that the glycogen produced in N-G+ medium had the longest average branch chain-length (DP10.4) among the conditions tested. When the yield and structure of glycogen were examined in different growth phases, the greatest yield (36.6 mg/g wet cell mass) and the longest branch chain-length (DP10.7) were observed 2 days after the fully grown cells in the N+G+ medium were transferred to the growth restricting (N-G+) medium.
Yoo
Sang-Ho
SH
Department of Food Science and Human Nutrition, Iowa State University, Ames, IA 50010, USA. shyoo@sejong.ac.kr
Keppel
Catherine
C
Spalding
Martin
M
Jane
Jay-lin
JL
D003470:Culture Media / Q000494:pharmacology; D005453:Fluorescence; D006003:Glycogen / Q000096:biosynthesis* / Q000737:chemistry* / Q000302:isolation & purification; D046529:Microscopy, Electron, Transmission; D046939:Synechocystis / Q000187:drug effects / Q000254:growth & development* / Q000378:metabolism* / Q000648:ultrastructure
D003470:Culture Media; D006003:Glycogen