부산대학교 도서관

The introduction of culture-independent molecular techniques clarified the following. First, there were many formerly unknown phylogenetic groups in the ocean. Also some groups, such as Archaea, for which their presence in marine environments had previously been unknown were found to commonly occur. Second, cultured microbes do not always represent the entirety of the population. For instance, microbes belonging to the genus Vibrio are often isolated and thoroughly investigated, but this group comprises only a very minor portion of the total population. Third, in marine environments, Bacteroidetes (phylum), alphaproteobacteria (class), gammaproteobacteria (class) usually comprise the major part of populations. In the upper water column, cyanobacteria (phylum) are also commonly found. One particular group, SAR11, that belongs to the alphaproteobacteria, is distributed quite widely over almost all part of the ocean. Fourth, the introduction of NGS clarified that in addition to some dominant phylogenetic groups, there are many minor groups existing at a low concentration of individuals. They are referred to as the, “rare biosphere”. Apparent species richness or the total number of unique sequences are dependent on those groups. It should be pointed out that it is now technically possible to recover mRNAs from the environment and analyze the sequences of such genes. This enables us to detect possible microbial functions that cannot be elucidated by DNA analyses.