Synechococcus elongatus PCC 7942

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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