@inproceedings{oai:jaxa.repo.nii.ac.jp:00013834,
 author = {三好, 達夫 and 長沼, 毅 and Miyoshi, Tatsuo and Naganuma, Takeshi},
 book = {宇宙利用シンポジウム　第20回　平成15年度, Space Utilization Research: Proceedings of the Twentieth Space Utilization Symposium},
 month = {Mar},
 note = {Existence of nanobacteria (often regarded as the bacteria that pass through 0.2 micrometer filters) has been increasingly acknowledged. However, their phylogenetic positions, physiological features and ecological significances are not fully understood. DNA was extracted from the 0.2 micrometer-filtrate groundwater (traditionally, all bacteria are supposed to be cut off) and PCR-amplified 16S rDNA genes, which were then cloned and sequenced for phylogenetic analyses. Most of the 16S rDNA were of unidentified bacteria and they formed new clade (branch) of the 'evolutionary tree'. One of the isolated/cultured bacteria from the 0.2 micrometer-filtrate was ascribed to the genus Microscilla, most of which species are known to form tiny spherical cells during senescence. Some of the 'aged' spheres became smaller than the filter pore size of 0.2 micrometer. Another example of the cultured nanobacteria was among the alpha-Proteobacteria, and the relationship with the tiny (but greater than 0.2 micrometer) alpha-Proteobacteria was suggested. As the some of the alpha-Proteobacteria are known as symbiotic or related to mitochondria, they may be able to switch their life styles between symbiotic and 'free-living'. So far, all the genomes having less than 1 million base pairs (less than 1 MB) are of symbiotic and parasitic microorganisms. If any 'free living' nanobacteria having less than 1 MB genomes they surely provide an ideal source for elucidating the 'minimum genomes for free living'. This would facilitate the search for life, or traces of life at least in exobiological environments., 資料番号: AA0046917029},
 pages = {88--89},
 publisher = {宇宙航空研究開発機構宇宙科学研究本部, Institute of Space and Astronautical Science, Japan Aerospace Exploration Agency (JAXA/ISAS)},
 title = {ナノバクテリアの存在とその宇宙生物学的意義},
 year = {2004}
}