Complete genome structure of the nitrogen-fixing symbiotic bacterium Mesorhizobium loti

Takakazu Kaneko, Yasukazu Nakamura, Shusei Sato, Erika Asamizu, Tomohiko Kato, Shigemi Sasamoto, Akiko Watanabe, Kumi Idesawa, Atsuko Ishikawa, Kumiko Kawashima, Takaharu Kimura, Yoshie Kishida, Chiaki Kiyokawa, Mitsuyo Kohara, Midori Matsumoto, Ai Matsuno, Yoko Mochizuki, Shinobu Nakayama, Naomi Nakazaki, Sayaka ShimpoMasako Sugimoto, Chie Takeuchi, Manabu Yamada, Satoshi Tabata

Research output: Contribution to journalArticlepeer-review

667 Citations (Scopus)


The complete nucleotide sequence of the genome of a symbiotic bacterium Mesorhizobium loti strain MAFF303099 was determined. The genome of M. loti consisted of a single chromosome (7, 036, 071 bp) and two plasmids, designated as pMLa (351, 911 bp) and pMLb (208, 315 bp). The chromosome comprises 6752 potential protein-coding genes, two sets of rRNA genes and 50 tRNA genes representing 47 tRNA species. Fifty-four percent of the potential protein genes showed sequence similarity to genes of known function, 21% to hypothetical genes, and the remaining 25% had no apparent similarity to reported genes. A 611-kb DNA segment, a highly probable candidate of a symbiotic island, was identified, and 30 genes for nitrogen fixation and 24 genes for nodulation were assigned in this region. Codon usage analysis suggested that the symbiotic island as well as the plasmids originated and were transmitted from other genetic systems. The genomes of two plasmids, pMLa and pMLb, contained 320 and 209 potential protein-coding genes, respectively, for a variety of biological functions. These include genes for the ABC-transporter system, phosphate assimilation, two-component system, DNA replication and conjugation, but only one gene for nodulation was identified.

Original languageEnglish
Pages (from-to)331-338
Number of pages8
JournalDNA Research
Issue number6
Publication statusPublished - 2000


  • Genome sequencing
  • Mesorhizobium loti strain MAFF303099
  • Nitrogen fixation
  • Nodulation
  • Plasmid
  • Symbiosis


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