Synechococcus elongatus PCC 7942
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Photo: L.A. Sherman and D.M. Sherman,
Purdue University

The freshwater cyanobacterium Synechococcus elongatus PCC 7942 holds a special place in the development of cyanobacterial molecular genetics. It was this isolate, previously known as Anacystis nidulans R2, that was the first cyanobacterium demonstrated to be reliably transformable by exogenously added DNA (32). Over the decades, many genetic tools have been developed for S. elongatus, and applied to other transformable cyanobacteria (1, 9, 16). Strain PCC 7942 is very closely related to, and considered the same species as, PCC 6301, which is the type strain for S. elongatus (13) and the first accession in the Pasteur Culture Collection ( It is an obligate photoautotroph (13), with a genome of approximately 2.7 Mb (15). Two plasmids (approximately 8 and 46 kb) have been sequenced entirely (GenBank accessions S89470 and AF441790, respectively). S. elongatus has been extensively studied by a multi-national research community with respect to: acquisition of inorganic carbon (2, 8, 20, 22, 33), transport and regulation of nitrogen compounds (19, 23, 36), response to iron deprivation (3, 7, 21, 24, 37), acclimation to a variety of nutrient stresses (5, 6, 12, 27, 28, 31, 35), and adaptation to environmental variations in temperature (11, 14, 25, 26, 30) and light intensity (4, 17, 18, 29, 31, 34, 35). In recent years, S. elongatus PCC 7942 has again taken a pioneering position, as the only developed model system for exploring the mechanism of a prokaryotic circadian clock (10). A companion project to the JGI draft sequence is a functional genomics project ( that aims to inactivate each gene in the genome and identify all loci that are important for circadian rhythms of gene expression in the organism.

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19. Lee HM, Vazquez-Bermudez MF, de Marsac NT. 1999. The global nitrogen regulator NtcA regulates transcription of the signal transducer PII (GlnB) and influences its phosphorylation level in response to nitrogen and carbon supplies in the cyanobacterium Synechococcus sp. strain PCC 7942. J. Bacteriol. 181: 2697-702
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21. Michel KP, Pistorius EK, Golden SS. 2001. Unusual regulatory elements for iron deficiency induction of the idiA gene of Synechococcus elongatus PCC 7942. J. Bacteriol. 183: 5015-24
22. Omata T, Gohta S, Takahashi Y, Harano Y, Maeda S. 2001. Involvement of a CbbR homolog in low CO2-induced activation of the bicarbonate transporter operon in cyanobacteria. J. Bacteriol. 183: 1891-8
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25. Sane PV, Ivanov AG, Sveshnikov D, Huner NP, Oquist G. 2002. A transient exchange of the photosystem II reaction center protein D1:1 with D1:2 during low temperature stress of Synechococcus sp. PCC 7942 in the light lowers the redox potential of QB. J. Biol. Chem. 277: 32739-45
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27. Sauer J, Gorl M, Forchhammer K. 1999. Nitrogen starvation in Synechococcus PCC 7942: involvement of glutamine synthetase and NtcA in phycobiliprotein degradation and survival. Arch. Microbiol. 172: 247-55
28. Sauer J, Schreiber U, Schmid R, Volker U, Forchhammer K. 2001. Nitrogen starvation-induced chlorosis in Synechococcus PCC 7942. Low-level photosynthesis as a mechanism of long-term survival. Plant Physiol. 126: 233-43
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33. Tchernov D, Helman Y, Keren N, Luz B, Ohad I, et al. 2001. Passive entry of CO2 and its energy-dependent intracellular conversion to HCO3- in cyanobacteria are driven by a photosystem I-generated deltamuH+. J. Biol. Chem. 276: 23450-5
34. Tsinoremas NF, Schaefer MR, Golden SS. 1994. Blue and red light reversibly control psbA expression in the cyanobacterium Synechococcus sp. strain PCC 7942. J. Biol. Chem. 269: 16143-7
35. van Waasbergen LG, Dolganov N, Grossman AR. 2002. nblS, a gene involved in controlling photosynthesis-related gene expression during high light and nutrient stress in Synechococcus elongatus PCC 7942. J. Bacteriol. 184: 2481-90
36. Vazquez-Bermudez MF, Paz-Yepes J, Herrero A, Flores E. 2002. The NtcA-activated amt1 gene encodes a permease required for uptake of low concentrations of ammonium in the cyanobacterium Synechococcus sp. PCC 7942. Microbiol. 148: 861-9
37. Webb R, Troyan T, Sherman D, Sherman LA. 1994. MapA, an iron-regulated, cytoplasmic membrane protein in the cyanobacterium Synechococcus sp. strain PCC7942. J. Bacteriol. 176: 4906-13