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Journal of Bacteriology, January 2001, p. 280-286, Vol. 183, No. 1
0021-9193/01/$04.00+0   DOI: 10.1128/JB.183.1.280-286.2001
Copyright © 2001, American Society for Microbiology. All rights reserved.

Effect on Heterocyst Differentiation of Nitrogen Fixation in Vegetative Cells of the Cyanobacterium Anabaena variabilis ATCC 29413

Teresa Thiel* and Brenda Pratte

Department of Biology, University of Missouri---St. Louis, St. Louis, Missouri 63121

Received 9 June 2000/Accepted 3 October 2000

Heterocysts are terminally differentiated cells of some filamentous cyanobacteria that fix nitrogen for the entire filament under oxic growth conditions. Anabaena variabilis ATCC 29413 is unusual in that it has two Mo-dependent nitrogenases; one, called Nif1, functions in heterocysts, while the second, Nif2, functions under anoxic conditions in vegetative cells. Both nitrogenases depended on expression of the global regulatory protein NtcA. It has long been thought that a product of nitrogen fixation in heterocysts plays a role in maintenance of the spaced pattern of heterocyst differentiation. This model assumes that each cell in a filament senses its own environment in terms of nitrogen sufficiency and responds accordingly in terms of differentiation. Expression of the Nif2 nitrogenase under anoxic conditions in vegetative cells was sufficient to support long-term growth of a nif1 mutant; however, that expression did not prevent differentiation of heterocysts and expression of the nif1 nitrogenase in either the nif1 mutant or the wild-type strain. This suggested that the nitrogen sufficiency of individual cells in the filament did not affect the signal that induces heterocyst differentiation. Perhaps there is a global mechanism by which the filament senses nitrogen sufficiency or insufficiency based on the external availability of fixed nitrogen. The filament would then respond by producing heterocyst differentiation signals that affect the entire filament. This does not preclude cell-to-cell signaling in the maintenance of heterocyst pattern but suggests that overall control of the process is not controlled by nitrogen insufficiency of individual cells.

* Corresponding author. Mailing address: Department of Biology, University of Missouri---St. Louis, St. Louis, MO 63121. Phone: (314) 516-6208. Fax: (314) 516-6233. E-mail: thiel{at}umsl.edu.

Journal of Bacteriology, January 2001, p. 280-286, Vol. 183, No. 1
0021-9193/01/$04.00+0   DOI: 10.1128/JB.183.1.280-286.2001
Copyright © 2001, American Society for Microbiology. All rights reserved.


This article has been cited by other articles:

  • Valladares, A., Flores, E., Herrero, A. (2008). Transcription Activation by NtcA and 2-Oxoglutarate of Three Genes Involved in Heterocyst Differentiation in the Cyanobacterium Anabaena sp. Strain PCC 7120. J. Bacteriol. 190: 6126-6133 [Abstract] [Full Text]  
  • Weyman, P. D., Pratte, B., Thiel, T. (2008). Transcription of hupSL in Anabaena variabilis ATCC 29413 Is Regulated by NtcA and Not by Hydrogen. Appl. Environ. Microbiol. 74: 2103-2110 [Abstract] [Full Text]  
  • Takaichi, S., Mochimaru, M., Maoka, T. (2006). Presence of Free Myxol and 4-Hydroxymyxol and Absence of Myxol Glycosides in Anabaena variabilis ATCC 29413, and Proposal of a Biosynthetic Pathway of Carotenoids. Plant Cell Physiol 47: 211-216 [Abstract] [Full Text]  
  • Khudyakov, I. Y., Golden, J. W. (2004). Different functions of HetR, a master regulator of heterocyst differentiation in Anabaena sp. PCC 7120, can be separated by mutation. Proc. Natl. Acad. Sci. USA 101: 16040-16045 [Abstract] [Full Text]  
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  • Yoon, H.-S., Golden, J. W. (2001). PatS and Products of Nitrogen Fixation Control Heterocyst Pattern. J. Bacteriol. 183: 2605-2613 [Abstract] [Full Text]  


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