[Phylogenetic analysis of intestinal bacterium using the distribution of intestinal bacterium in cyprinidate fishes and 16S DNA sequence data set].

There is a complex- and multi-effect for interdependent survival between intestinal- microorganisms and hosts. The symbiosis or coevolution that results from this effect for interdependent survival is used to reveal the phylogenies of hosts as well as intestinal microorganisms. The symbiosis or coevolution between intestinal microorganisms and hosts has been generated by interactive natural selection occurred between them. The symbiosis information that has been formed by interactive natural selection during a long evolutionary process must be recorded in DNA sequences. According to this point of view,we analyzed the phylogeny of 9 intestinal bacteria genera using their contents in intestines of 8 Cyrinidate species. At the same time,we fetched the 16S rRNA gene DNA sequences of 43 intestinal bacteria species being included in these nine genera of six intestinal families from GeneBank and constructed phylogenetic trees by NJ and MP methods. The NJ tree and MP tree have the same topologic configuration and are identical with the classical phylogenetic tree. Both the trees of 16S rRNA gene separated 43 bacteria species into gram-negative bacteria group and the gram-positive bacteria group,which are the first branches. Each of the first branches (groups) made again 6 subbranches (subgroups) where each subbranch is a family.Especially,the subbranch (subgroup) of enterobacteriaceace made again four small branches as genus taxon. This tree also shows that bacilliform bacterium is distinct from each other in the NJ and MP trees. After all species on the tree are merged,the topological configuration of the unrooted tree of 16S gene is closed to that of the host range unrooted tree.However,the position of bacillus is greatly changed on both the unrooted trees. The difference can be found if we increase the examination level and extend the hosts examed.