HETEROCYST DEVELOPMENT AND LOCALIZATION OF CYANOPHYCIN IN N2-FIXING CULTURES OF ANABAENA SP. PCC 7120 (CYANOBACTERIA)
Article first published online: 25 DEC 2001
Phycological Society of America, Inc.
Journal of Phycology
Volume 36, Issue 5, pages 932–941, October 2000
How to Cite
Sherman, D. M., Tucker, D. and Sherman, L. A. (2000), HETEROCYST DEVELOPMENT AND LOCALIZATION OF CYANOPHYCIN IN N2-FIXING CULTURES OF ANABAENA SP. PCC 7120 (CYANOBACTERIA). Journal of Phycology, 36: 932–941. doi: 10.1046/j.1529-8817.2000.99132.x
- Issue published online: 31 JAN 2003
- Article first published online: 25 DEC 2001
- 1 Received 23 July 1999. Accepted 10 July 2000.
- N2 fixation;
The process of N2 fixation in the filamentous cyanobacterium Anabaena sp. PCC 7120 is known to occur in terminally differentiated cells called heterocysts. This study is concerned with a morphological and immunocytochemical analysis of the developing heterocysts. The heterocysts continue a developmental process after synthesis of the specialized cell wall and the formation of the proheterocyst. The initial stages were described by Wilcox et al. (1973) and designated stages 1 through 7, with stages 5–7 associated with the maturing heterocyst. We now designate a stage 8 as the postmaturation stage, based on physiological and ultrastructural evidence. Immunocytochemistry to detect the nitrogenase protein NifH and the nonribosomally synthesized polypeptide cyanophycin demonstrated a complementary accumulation of these polypeptides. Accumulation of the nitrogenase protein was greatest at stages 5 and 6 and then declined precipitously. Cyanophycin was more prevalent after late stage 6 and was primarily associated with the polar nodule (polar plug) and the neck connecting the heterocyst with the adjoining vegetative cell. We suggest that the cyanophycin-containing polar plug is a key intermediate in the storage of fixed nitrogen in the heterocyst, a result consistent with the suggestion first made by Carr (1988) that cyanophycin exists as a dynamic reservoir of fixed nitrogen within the heterocysts.