抗寄生虫薬avermectin の生産菌として知られているStreptomyces avermitilis ATCC 31267^T のゲノム配列が2001 年に論文発表され（Omura et al., 2001），同基準株S. avermitilis MA-4680^T の全ゲノム配列として9 Mb の染色体と94 kb のプラスミドSAP1 のDNA 配列がGenBank/EMBL/DDBJ で公開されている（Ikeda et al., 2003）．今回MA-4680^T に由来するS. avermitilis NBRC 14893^T のゲノムDNA を鋳型としたPCR で，公開されているゲノム配列には存在しない未知のNRPS 遺伝子が増幅するという不可解な現象が確認された．その原因を調べるためにNBRC 14893^T をゲノム解析した結果，公開されているゲノム配列には存在しない配列を見出した．この中には約40 kb のNRPS 遺伝子クラスターや約65 kb のNRPS/PKS ハイブリッド遺伝子クラスターが存在し，それぞれdemethylcomplestatin と新規oxazolomycin 類縁体の生合成に関与することが示唆された．S. avermitilis の基準株（MA-4680^T）はAgricultural Research Service Culture Collection（NRRL） を経た後に，KCC Culture Collection of Actinomycetes, Kaken Pharmaceutical Co., Ltd.（KCC）とAmerican Type Culture Collection（ATCC）に渡っている．NBRC 14893^T はKCC 株に由来し，2001 年のゲノム解読株はATCC 株に由来している．Streptomyces ではプラスミドの欠落やゲノムの組換えなどが容易に起こり得るので，本研究で見出した2 つの生合成遺伝子クラスターは基準株がNRRL からATCC に渡った後のどこかの段階で欠落したのであろう．

In the case of the genus Agrobacterium, which comprises crown gall bacteria and hairy root bacteria, the genus and species have been artificially defined based on pathogenic characters. For some species of the genus, several biovars, equivalent to the rank of variety level, have been established. Recently, based on the results of polyphasic taxonomic approaches, it was proposed that each biovar should be elevated to the species level (Sawada et al., IJSB 43: 694-702, 1993; Ophel & Kerr, IJSB 40: 236-241, 1990), and that the genera Agrobacterium and Rhizobium should be amalgamated into one single genus Rhizobium (Young et al., IJSEM 51: 89-103, 2001). Taking these changes in the taxonomic situation into consideration, strains belonging to the phytopathogenic Rhizobium species (formerly Agrobacterium species) preserved in the NIAS Genebank were re-identified based on phylogenetic analyses using 16S rDNA, atpD, glnA and recA, inoculation tests, PCR assays and so on, and some of them with typical characters for each species/pathogenic state/genomovar were selected as approved strains (reference strains for taxonomic studies). In addition, for every host plant, we chose pathogenic strains that were proved to harbor Ti or Ri plasmids, as approved strains (reference strains for inoculation tests). The DNA sequence data of the strains are provided by the NIAS Genebank database (http://www.gene.affrc.go.jp/databases-micro_search_en.php).