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Bacteriophages (phages), potentially the most numerous "organisms" on Earth, are the viruses of bacteria (more generally, of prokaryotes〔The term "prokaryotes" is useful to mean the sum of the bacteria and archaea but otherwise can be controversial, as discussed by ; see also pp. 103–4 of provides a history.〕). Phage ecology is the study of the interaction of bacteriophages with their environments.〔This article on phage ecology was expanded from a stub during the writing of the first chapter of the edited monograph, ''Bacteriophage Ecology'' (forecasted publication date: March, 2008, Cambridge University Press), in order to be cited by that chapter especially as a repository of phage ecology review chapters and articles.〕 == Introduction to phage ecology == === Vastness of phage ecology === Phages are obligate intracellular parasites meaning that they are able to reproduce only while infecting bacteria. Phages therefore are found only within environments that contain bacteria. Most environments contain bacteria, including our own bodies (called normal flora). Often these bacteria are found in large numbers. As a consequence, phages are found almost everywhere. As a rule of thumb, many phage biologists expect that phage population densities will exceed bacterial densities by a ratio of 10-to-1 or more (VBR or virus-to-bacterium ratio; see for a summary of actual data). As there exist estimates of bacterial numbers on Earth of approximately 1030, there consequently is an expectation that 1031 or more individual virus (mostly phage) particles exist (), making phages the most numerous category of "organisms" on our planet. Bacteria (along with archaea) appear to be highly diverse and there possibly are millions of species. Phage-ecological interactions therefore are quantitatively vast: huge numbers of interactions. Phage-ecological interactions are also qualitatively diverse: There are huge numbers of environment types, bacterial-host types, and also individual phage types). 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Phage ecology」の詳細全文を読む スポンサード リンク
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