Some Aspects of Structure and Function in N Fixing Cyanobacteria

Stewart, W. D. P.

doi:10.1146/annurev.mi.34.100180.002433

Cited by 326 publications

(172 citation statements)

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“…The morphological and ultrastructural observations on Lichina confinis reported in the present study (Figs 1, 2) are similar to those of Lichina pygmaea (Peveling, 1973) and are consistent with earlier observations on free-living and lichenized cyanobacteria (see Stewart, 1980;Ahmadjian, 1982;Rai, 19906;Honegger, 1991). Various types of haustoria and vesicles have been reported in a number of lichens with unicellular and heterocystous cyanobionts (Paran, Ben-Shaul & Galun, 1971 ;Peveling, 1973;Marton & Galun, 1976;Bergman & HussDanell, 1983;Budel & Rhiel, 1987;Rai, 1990fe;Honegger, 1991).…”

Section: Discussionsupporting

confidence: 92%

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The marine lichen Lichina confinis (O. F. Müll.) C. Ag.: ultrastructure and localization of nitrogenase, glutamine synthetase, phycoerythrin and ribulose 1, 5‐bisphosphate carboxylase/oxygenase in the cyanobiont

1993

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SUMMARYThallus ultrastructure and the localization of proteins involved in photosynthesis, N^ fixation and animonia assimilation was studied in the Lichina confinis (O. F. Mull) C. Ag.-Calothrix symbiosis. The lichen thallus showed profuse branching. Within this, the cyanobiont was located in the cortical zone. Haustoria were frequently observed in contact with vegetative cells of the cyanobiont but not with heterocysts. An extensive mucilage layer containing numerous vesicles occurred around cyanobiont cells. Immunolabelling showed nitrogenase to be exclusively located in heterocysts of the cyanobiont and the free-living Calothrix sp. Glutamine synthetase (GS) levels in the cyanobiont were found to be drastically decreased compared to the levels in free-living (cultured) Calothrix sp. Such a decrease was more prominent in mature parts of the thallus than in the apical region. Rubisco was mostly located in carboxysomes of the vegetative cells of the cyanobiont. There were relatively low levels of Rubisco in tbe cytoplasm of vegetative cells, wbile heterocysts sbowed negligible levels. In free-living (cultured) Calothrix sp., pbycoerytbrin (PE) was found to be located along tbe tbylakoid membranes both in vegetative cells and beterocysts. Cyanobiont cells sbowed a similar pattern but tbe levels were relatively lower.

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Section: Discussionsupporting

confidence: 92%

“…GS is the primary ammonia-assimilating enzyme in cyanobacteria (Wolk e? a/., 1976;Haselkorn, 1978;Stewart, 1980). In cyanobacterial-plant symbioses, where N^-derived ammonia is liberated by the cyanobiont (e.g.…”

Section: Discussionmentioning

confidence: 99%

The marine lichen Lichina confinis (O. F. Müll.) C. Ag.: ultrastructure and localization of nitrogenase, glutamine synthetase, phycoerythrin and ribulose 1, 5‐bisphosphate carboxylase/oxygenase in the cyanobiont

1993

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“…In many species of filamentous cyanobacteria protection is achieved by compartmentalization of nitrogenase into heterocysts (Stewart, 1980). Gloeothece is a unicellular cyanobacterium which fixes Nz aerobically but does not produce heterocysts.…”

Section: Introductionmentioning

confidence: 99%

Nitrogen Fixation by Gloeothece sp. PCC 6909: Respiration and Not Photosynthesis Supports Nitrogenase Activity in the Light

et al. 1986

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Nitrogenase activity of suspensions of the unicellular cyanobacterium Gloeothece sp. PCC 6909 plotted against the concentration of dissolved 0, (do,) resulted in a bell-shaped curve, both in the light and in the dark, with optima of 25 or 80 ~M -O , depending on the age of the culture, At the optimum d o 2 , nitrogenase activity [typically 4 to 6 nmol C2H, (mg protein)-' min-l] was similar in the light or in the dark. Alteration of light intensity from zero to 2 klx, or addition of 3-(3,4-dichlorophenyl)-l, 1-dimethylurea (DCMU), had no effect on nitrogenase activity. At 1 klx the ADP/ATP ratio was 0.2 and showed only a marginal increase as the d o 2 was increased. However, a high level of illumination (30 klx) stimulated or inhibited nitrogenase activity, depending on the external do,, presumably as a consequence of changes in the intracellular O2 concentration; in the presence of DCMU, activity increased twofold, independent of do,.In the dark, the dependence of the rate of respiration on O2 concentration suggested the presence of three 0,-uptake systems with apparent K, values of 1 PM, 5 p~ and 25 p~. The ADP/ATP ratio under anaerobic conditions was 0.47 and showed a marked decrease as d o 2 was increased to 25 VM. A CN-insensitive respiratory activity, which neither supported nitrogenase activity nor was coupled to ATP synthesis, was associated with the system with the apparent K, of 5 p~. The dependence of the specific activity of nitrogenase on d o 2 indicated that both the high affinity ( K , 1 WM) and low affinity ( K , 25 p~) O2-uptake systems contributed ATP or reductant for N,-fixation. KCN (2.5 mM) completely inhibited nitrogenase activity in the dark and at moderate levels of illumination and d o 2 . We conclude that respiration is the major source of reductant and ATP for nitrogenase activity both in the dark and in the light, but that photosystem I can contribute ATP at very high levels of illumination.

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“…Other structural changes include the reorganization of photosynthetic membranes and the formation of specialized junctions with neighboring vegetative cells. Many biochemical changes occur in the heterocyst, including the inactivation of ribulose bisphosphate carboxylase and the oxygen-evolving photosystem II (PSII) photochemical reaction center complex, and the induction of genes involved in nitrogen fixation and its support, such as the oxidative pentose pathway and a heterocyst-specific ferredoxin (Winkenbach and Wolk 1973;Haselkorn 1978;Stewart 1980;Wolk 1982;Carr 1983;Bohme and Haselkorn 1988).…”

mentioning

confidence: 99%

Characterization of a gene controlling heterocyst differentiation in the cyanobacterium Anabaena 7120.

Buikema¹,

Haselkorn²

1991

Genes Dev.

307

360

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Anabaena 7120 mutant 216 fails to differentiate heterocysts. We previously identified a 2.4-kb wild-type DNA fragment able to complement this mutant. We show here that the sequence of this fragment contains a single open reading frame [hetR), encoding a 299-amino-acid protein. Conjugation of deletion subclones of this fragment into strain 216 showed that the /ieti?-coding region is both necessary and sufficient for complementation of the Het~ phenotype. The mutation in 216 is located at nucleotide 535 in the betR gene, converting a serine at position 179 in the wild-type protein to an asparagine in the mutant. Interruption of the hetR gene in wild-type cells results in a mutant phenotype identical to that of 216. Both 216 and wild-type cells containing wild-type hetR on a plasmid display increased frequency of heterocysts, even on media containing fixed nitrogen. These results suggest that hetR encodes a product that is not only essential for but also controls heterocyst development. This putative regulatory protein lacks known structural motifs characteristic of transcription factors and probably acts at a level one or more steps removed from its target genes.

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Some Aspects of Structure and Function in N Fixing Cyanobacteria

Cited by 326 publications

References 1 publication

The marine lichen Lichina confinis (O. F. Müll.) C. Ag.: ultrastructure and localization of nitrogenase, glutamine synthetase, phycoerythrin and ribulose 1, 5‐bisphosphate carboxylase/oxygenase in the cyanobiont

The marine lichen Lichina confinis (O. F. Müll.) C. Ag.: ultrastructure and localization of nitrogenase, glutamine synthetase, phycoerythrin and ribulose 1, 5‐bisphosphate carboxylase/oxygenase in the cyanobiont

Nitrogen Fixation by Gloeothece sp. PCC 6909: Respiration and Not Photosynthesis Supports Nitrogenase Activity in the Light

Characterization of a gene controlling heterocyst differentiation in the cyanobacterium Anabaena 7120.

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