Growth,photosynthesis, nitrogen fixation and carbohydrate production by a unicellular cyanobacterium,Synechococcus sp. (Cyanophyta)

A polymer-producing strain of unicellular cyanobacteria, Synechococcus sp., was isolated from a coastal lagoon in Florida. This strain, designated BG0011, excreted a highly viscous polysaccharide. Maximum observed growth rates for BG0011 were 2.5 div. day^-2. BG0011 also exhibited nitrogen fixation (nitrogenase) activity under aerobic conditions and grew at near maximum rates in medium lacking reduced nitrogen. Growth and carbohydrate production were enhanced by carbon dioxide enrichment. Rheological study of the extracellular polysaccharide revealed a viscosity versus shear rate curve similar in shape to that of xanthan gum. Maximum observed rate of carbohydrate production was 1 g dry weight liter^-1 month^-1.