Journal Article

Complete Genomic Structure of the Bloom-forming Toxic Cyanobacterium <i>Microcystis aeruginosa</i> NIES-843

Takakazu Kaneko, Nobuyoshi Nakajima, Shinobu Okamoto, Iwane Suzuki, Yuuhiko Tanabe, Masanori Tamaoki, Yasukazu Nakamura, Fumie Kasai, Akiko Watanabe, Kumiko Kawashima, Yoshie Kishida, Akiko Ono, Yoshimi Shimizu, Chika Takahashi, Chiharu Minami, Tsunakazu Fujishiro, Mitsuyo Kohara, Midori Katoh, Naomi Nakazaki, Shinobu Nakayama, Manabu Yamada, Satoshi Tabata and Makoto M. Watanabe

in DNA Research

Published on behalf of Kazusa DNA Research Institute

Volume 14, issue 6, pages 247-256
Published in print January 2007 | ISSN: 1340-2838
Published online January 2008 | e-ISSN: 1756-1663 | DOI: http://dx.doi.org/10.1093/dnares/dsm026

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Abstract

The nucleotide sequence of the complete genome of a cyanobacterium, Microcystis aeruginosa NIES-843, was determined. The genome of M. aeruginosa is a single, circular chromosome of 5 842 795 base pairs (bp) in length, with an average GC content of 42.3%. The chromosome comprises 6312 putative protein-encoding genes, two sets of rRNA genes, 42 tRNA genes representing 41 tRNA species, and genes for tmRNA, the B subunit of RNase P, SRP RNA, and 6Sa RNA. Forty-five percent of the putative protein-encoding sequences showed sequence similarity to genes of known function, 32% were similar to hypothetical genes, and the remaining 23% had no apparent similarity to reported genes. A total of 688 kb of the genome, equivalent to 11.8% of the entire genome, were composed of both insertion sequences and miniature inverted-repeat transposable elements. This is indicative of a plasticity of the M. aeruginosa genome, through a mechanism that involves homologous recombination mediated by repetitive DNA elements. In addition to known gene clusters related to the synthesis of microcystin and cyanopeptolin, novel gene clusters that may be involved in the synthesis and modification of toxic small polypeptides were identified. Compared with other cyanobacteria, a relatively small number of genes for two component systems and a large number of genes for restriction-modification systems were notable characteristics of the M. aeruginosa genome.

Keywords: cyanobacterium; M. aeruginosa; microcystin; water bloom; genome sequence

Journal Article.  5599 words.  Illustrated.

Subjects: Genetics and Genomics

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