This Article Full Text Full Text (PDF) Other Versions of this Article: JB.00220-07v1 189/12/4425    most recent Alert me when this article is cited Alert me if a correction is posted Services Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Reprints and Permissions Copyright Information Books from ASM Press MicrobeWorld Citing Articles Citing Articles via HighWire Citing Articles via Google Scholar Google Scholar Articles by Valladares, A. Articles by Herrero, A. Search for Related Content PubMed PubMed Citation Articles by Valladares, A. Articles by Herrero, A.

Heterocyst Development and Diazotrophic Metabolism in Terminal Respiratory Oxidase Mutants of the Cyanobacterium Anabaena sp. Strain PCC 7120

Instituto de Bioquímica Vegetal y Fotosíntesis, Consejo Superior de Investigaciones Científicas y Universidad de Sevilla, E-41092 Seville, Spain,¹ Lehrstuhl für Zellbiologie und Pflanzenphysiologie, Universität Regensburg, D-93040 Regensburg, Germany²

Received 9 February 2007/ Accepted 30 March 2007

Heterocyst development was analyzed in mutants of the heterocyst-forming cyanobacterium Anabaena sp. strain PCC 7120 bearing inactivated cox2 and/or cox3 genes, encoding heterocyst-specific terminal respiratory oxidases. At the morphological level, the cox2 cox3 double mutant (strain CSAV141) was impaired in membrane reorganization involving the so-called honeycomb system that in the wild-type strain is largely or exclusively devoted to respiration, accumulated glycogen granules at conspicuously higher levels than the wild type (in both vegetative cells and heterocysts), and showed a delay in carboxysome degradation upon combined nitrogen deprivation. Consistently, chemical analysis confirmed higher accumulation of glycogen in strain CSAV141 than in the wild type. No impairment was observed in the formation of the glycolipid or polysaccharide layers of the heterocyst envelope, consistent with the chemical detection of heterocyst-specific glycolipids, or in the expression of the heterocyst-specific genes nifHDK and fdxH. However, nitrogenase activity under oxic conditions was impaired in strain CSAV135 (cox3) and undetectable in strain CSAV141 (cox2 cox3). These results show that these dedicated oxidases are required for normal development and performance of the heterocysts and indicate a central role of Cox2 and, especially, of Cox3 in the respiratory activity of the heterocysts, decisively contributing to protection of the N₂ fixation machinery against oxygen. However, in contrast to the case for other diazotrophic bacteria, expression of nif genes in Anabaena seems not to be affected by oxygen.

Published ahead of print on 6 April 2007.

This article has been cited by other articles:

• Toepel, J., Welsh, E., Summerfield, T. C., Pakrasi, H. B., Sherman, L. A. (2008). Differential Transcriptional Analysis of the Cyanobacterium Cyanothece sp. Strain ATCC 51142 during Light-Dark and Continuous-Light Growth. J. Bacteriol. 190: 3904-3913 [Abstract] [Full Text]