Kaneko T, Nakamura Y, Sato S, Asamizu E, Kato T, Sasamoto S, Watanabe A, Idesawa K, Ishikawa A, Kawashima K, Kimura T, Kishida Y, Kiyokawa C, Kohara M, Matsumoto M, Matsuno A, Mochizuki Y, Nakayama S, Nakazaki N, Shimpo S, Sugimoto M, Takeuchi C, Yamada M, Tabata S
Kazusa DNA Research Institute, Kisarazu, Chiba , Japan.
DNA Res. 2000 Dec 31;7(6):331-8. doi: 10.1093/dnares/7.6.331.
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.
共生细菌百脉根中生根瘤菌MAFF303099株的基因组全核苷酸序列已被测定。百脉根中生根瘤菌的基因组由一条染色体（7,036,071 bp）和两个质粒组成，分别命名为pMLa（351,911 bp）和pMLb（208,315 bp）。该染色体包含6752个潜在的蛋白质编码基因、两套rRNA基因以及代表47种tRNA的50个tRNA基因。54%的潜在蛋白质基因与已知功能的基因具有序列相似性，21%与假定基因相似，其余25%与已报道基因无明显相似性。一个611 kb的DNA片段被鉴定为共生岛的极有可能的候选片段，该区域分配了30个固氮基因和24个结瘤基因。密码子使用分析表明，共生岛以及质粒起源于其他遗传系统并从其他遗传系统传递而来。两个质粒pMLa和pMLb的基因组分别包含320个和209个潜在的蛋白质编码基因，具有多种生物学功能。这些功能包括ABC转运系统、磷酸盐同化、双组分系统、DNA复制和接合相关基因，但仅鉴定出一个结瘤基因。
