Gram-negative anaerobic rods, especially the genus Bacteroides, are part of the indigenous microbiota of the human and animal gastrointestinal tract, but different species in this group are commonly associated with a variety of human and animal infections. The genus Bacteroides is an important bacteria group in clinical bacteriology. In the past, because of poor definition of the genus, more than 50 species of Bacteroides have been included in this group. In the late 1980s, many techniques were applied and further reinforced the considerable inter- and intraspecies diversity of this genus. DNA base composition, which is considered the most reliable criterion for circumscribing the limits of a genus, provided the impetus to restructure the genus, which then comprised species that possessed mol% G+C contents of 28 and 61. Consequently the genus Bacteroides was redefined to encompass species that formed a cluster that was phenotypically and genetically akin to the type species, B. fragilis. Subsequently, two other large groups of species, Porphyromonas and Prevotella, were proposed together with several monospecific genera. In this study, we propose novel genera such as Barnesiella, Parabacteroides and Tannerella. In addition, nine novel Bacteroides species (B. coprocola, B. coprophilus, B. barnesiae, B. dorei, B. finegoldii, B. gallinarum, B. intestinalis, B. plebeius, and B. salanitronis) and seven novel Prevotella species (P. copri, P. multiformis, P. multisaccharivorax, P. pleuritidis, P. salivae, P. shahii, and P. stercorea) are proposed.

米国ジョージワシントン大学医学部 R. Hugh 教授から理研バイオリソースセンター微生物材料開発室 (IJCM) に寄託された未同定 Pseudomonas 属関連菌株の再同定を行った．臨床材料，動物および環境由来の未同定 49 菌株の 16S rRNA 遺伝子による系統解析，リボタイビング解析および生理生化学的性状検査を行った．16S rRNA 遺伝子の系統解析では，Shewanella algae に属する 2 株を除いて，Pseudomonas 属であることが認められ，64%（47 株中 30 株）を Pseudomonas aeruginosa, P. pseudoalcaligenes, P. stutzeri および P. alcaliphila に同定した．残り 36%（17 株）は既存菌種に同定することは困難であった．これらのグループは 16S rRNA 遺伝子による系統解析で菌種間で 99% 以上の高い相同性を示すが，表現性状およびリボタイピングにおいては菌株間で多様な性状を示した．以上の成績は Pseudomonas 属に属する菌株における有効な菌種同定法の開発が急務であることを示唆している．