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The thermophile Thermosynechococcus elongatus BP-1 has joined the ranks of cyanobacteria with completed genome sequences. It is the third cyanobacterial genome completed by the Kazusa DNA Research Institute, (which has also completed the genomes of Synechocystis PCC 6803 and Nostoc PCC 7120). With the finished genomes of Prochlorococcus marinus MED4 and MIT9313, the number of completed cyanobacterial genomes has now swelled to 5 (see progress report on cyanobacterial genome projects).
The size of the circular chromosome of 2,593,857 nucleotides and no other replicons were found. This genome size is similar to that reported for Synechococcus WH8102, but the T. elongatus genome has several unusual features. First, the genome is relatively deficient in fatty acid desaturases. Whilc Synechocystis PCC 6803 possesses four types of desaturases -- desA, desB, desC, and desD -- and both Nostoc PCC 7120 and Nostoc punctiforme possess the first three, T. elongatus has only desC. This and a relatively high number of heat-shock proteins is consistent with the cyanobacterium's high temperature life style.
A second unusual feature is the presence of 28 copies of group II introns in the T. elongatus genome. Group I introns are well known in cyanobacteria and and chloroplasts, lying within the tRNALeu gene, but this may be the first reported instance of self-splicing group II introns.
A description of the genome has been published [Nakamura
et al (2002) DNA Research 9:123-130].