Ultrastructural and chemical assessment of poly-beta-hydroxybutyric acid in the marine cyanobacterium Trichodesmium thiebautii.

We report here on the occurrence and quantities of poly-beta-hydroxybutyric acid (PHB) in natural populations of the marine cyanobacterium Trichodesmium thiebautii. A diurnal variation in the shape and size of PHB granules and in PHB content was observed. The highest PHB levels (2.3 +/- 0.8 mg g-1 dry wt) were recorded in the early morning and the values decreased thereafter with a minimum at night (1.6 +/- 0.9 mg g-1 dry wt). Our data suggest that PHB is a prominent cell constituent in T. thiebautii and that its synthesis takes place in the early morning whereas it is utilized during the rest of the day.