Reconciling the incompatible: N<sub>2</sub> fixation And O<sub>2</sub>

Gallon, John

doi:10.1111/j.1469-8137.1992.tb00087.x

Cited by 386 publications

(291 citation statements)

References 286 publications

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“…As nitrogenase is extremely sensitive to O 2 , diazotrophic cyanobacteria must avoid inactivation of nitrogen fixation by the O 2 produced in photosynthesis (Fay, 1992;Gallon, 1992;Stal and Zehr, 2008). Many filamentous diazotrophic cyanobacteria develop specialized N 2 -fixing cells, called heterocysts (Fay, 1992) that do not evolve O 2 .…”

Section: Introductionmentioning

confidence: 99%

Genome-wide analysis of diel gene expression in the unicellular N2-fixing cyanobacterium Crocosphaera watsonii WH 8501

et al. 2010

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The unicellular cyanobacterium Crocosphaera watsonii is an important nitrogen fixer in oligotrophic tropical and subtropical oceans. Metabolic, energy and cellular processes in cyanobacteria are regulated by the circadian mechanism, and/or follow the rhythmicity of light-dark cycles. The temporal separation of metabolic processes is especially essential for nitrogen fixation because of inactivation of the nitrogenase by oxygen. Using a microarray approach, we analyzed gene expression in cultures of Crocosphaera watsonii WH 8501 (C. watsonii) over a 24-h period and compared the whole-genome transcription with that in Cyanothece sp. ATCC 51142 (Cyanothece), a unicellular diazotroph that inhabits coastal marine waters. Similar to Cyanothece, regulation at the transcriptional level in C. watsonii was observed for all major metabolic and energy processes including photosynthesis, carbohydrate and amino acid metabolisms, respiration, and nitrogen fixation. Increased transcript abundance for iron acquisition genes by the end of the day appeared to be a general pattern in the unicellular diazotrophs. In contrast, genes for some ABC transporters (for example, phosphorus acquisition), DNA replication, and some genes encoding hypothetical proteins were differentially expressed in C. watsonii only. Overall, C. watsonii showed a higher percentage of genes with light-dark cycling patterns than Cyanothece, which may reflect the habitats preferences of the two cyanobacteria. This study represents the first whole-genome expression profiling in cultivated Crocosphaera, and the results will be useful in determining the basal physiology and ecology of the endemic Crocosphaera populations.

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Section: Introductionmentioning

confidence: 99%

Genome-wide analysis of diel gene expression in the unicellular N2-fixing cyanobacterium Crocosphaera watsonii WH 8501

et al. 2010

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“…The catalytic Fe 4 S 4 centers of the nitrogenase are irreversibly damaged by oxygen in vitro (53). Oxygen also represses transcription of nitrogenase genes (54). Furthermore, any reactive oxygen species generated by photosynthesis also affects the integrity of nitrogenase (55).…”

Section: Discussionmentioning

confidence: 99%

An Atypical psbA Gene Encodes a Sentinel D1 Protein to Form a Physiologically Relevant Inactive Photosystem II Complex in Cyanobacteria

Wegener¹,

Nagarajan²,

Pakrasi

2015

Journal of Biological Chemistry

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Background: Unicellular cyanobacteria separate photosynthesis and nitrogen fixation using a day-night cycle. Results: Cyanothece 51142 expresses a D1 protein exclusively in the dark period that assembles nonfunctional photosystem II. Conclusion:The unusual D1 is named sentinel D1 because it prevents photosynthesis from occurring during nitrogen fixation. Significance: Expression of sentinel D1 allows photosynthesis and nitrogen fixation to coexist in the cell.

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“…As nitrogenase (EC 1.18.6.1), the enzyme complex (the Feprotein, and a-and b-subunits of the MoFe-protein) that catalyses N 2 -fixation, is extremely labile to molecular oxygen (O 2 ) (Postgate, 1998), cyanobacteria have developed many strategies to separate N 2 -fixation and photosynthesis spatially or temporally (Bergman et al, 1997;Fay, 1992;Gallon, 1992;Wolk, 1999). Most unicellular diazotrophic cyanobacteria fix N 2 during the dark phase of light/dark cycles or in the night under atmospheric conditions (Gallon & Chaplin, 1988;Mitsui et al, 1986;Reddy et al, 1993;Taniuchi & Ohki, 2007).…”

Section: Introductionmentioning

confidence: 99%

Diazotrophy under continuous light in a marine unicellular diazotrophic cyanobacterium, Gloeothece sp. 68DGA

et al. 2008

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Nitrogenase is extremely sensitive to molecular oxygen (O 2 ), and unicellular diazotrophic cyanobacteria separate nitrogen (N 2 )-fixation and photosynthesis to protect nitrogenase from O 2 produced by photosynthesis. When grown under 12 h light/12 h dark cycles (LD), the marine unicellular diazotrophic cyanobacterium Gloeothece sp. 68DGA expressed the nitrogenase protein and its activity (acetylene reduction activity) only during the dark phase. However, this strain was able to grow diazotrophically under continuous light (CL). To determine whether nitrogenase synthesis and N 2 -fixation are temporally separated from photosynthesis in the Gloeothece cells that have fully acclimated to CL, the proportion of cells containing nitrogenase (the Fe-protein of nitrogenase) in the culture was measured using an immunocytochemical technique. Cells were grown in a continuous-culture device to maintain constant cell density. Under LD, the cells showed diurnal oscillation of nitrogenase activity, photosynthesis, respiration and the expression and the abundance of the Fe-protein. The oscillation was gradually reduced after the transfer of the cells to CL, and was lost after 23-25 days of cultivation under CL. In CL-acclimated cultures, the Fe-protein was always detected in about 94 % of the cells, although the nitrogenase activity was about one-third of the maximum activity in LD-acclimated cultures. These results suggest that synthesis of nitrogenase proceeds without diurnal oscillation in the CL-acclimated cells of Gloeothece sp. 68DGA. As the respiration rate in CL-acclimated culture was as high as the maximum rate observed in LD-acclimated culture, O 2 -uptake mechanism(s) may have been upregulated to maintain low intracellular pO 2 .

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Reconciling the incompatible: N₂ fixation And O₂

Cited by 386 publications

References 286 publications

Genome-wide analysis of diel gene expression in the unicellular N2-fixing cyanobacterium Crocosphaera watsonii WH 8501

Genome-wide analysis of diel gene expression in the unicellular N2-fixing cyanobacterium Crocosphaera watsonii WH 8501

An Atypical psbA Gene Encodes a Sentinel D1 Protein to Form a Physiologically Relevant Inactive Photosystem II Complex in Cyanobacteria

Diazotrophy under continuous light in a marine unicellular diazotrophic cyanobacterium, Gloeothece sp. 68DGA

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Reconciling the incompatible: N2 fixation And O2

Cited by 386 publications

References 286 publications

Genome-wide analysis of diel gene expression in the unicellular N2-fixing cyanobacterium Crocosphaera watsonii WH 8501

Genome-wide analysis of diel gene expression in the unicellular N2-fixing cyanobacterium Crocosphaera watsonii WH 8501

An Atypical psbA Gene Encodes a Sentinel D1 Protein to Form a Physiologically Relevant Inactive Photosystem II Complex in Cyanobacteria

Diazotrophy under continuous light in a marine unicellular diazotrophic cyanobacterium, Gloeothece sp. 68DGA

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Reconciling the incompatible: N₂ fixation And O₂