[Geographical distribution of magnetotactic bacteria].

Magnetotactic bacteria (MTB) are widely distributed in aquatic environments. To assess the correlation between their evolutionary relatedness and geographic distribution, we analyzed 239 16S rDNA sequences available in the Genbank, and constructed phylogenetic trees based on the sequences. After elimination of redundant sequences by grouping those with identity > 97% into a single one, we analyzed in detail total 139 16S rDNA sequences, including 55 from marine MTB and 82 from freshwater sequences, and belonging to Proteobacteria and Nitrospirae. Phylogeny analysis based on those sequences suggests that the geographical distribution of MTB has certain regional distribution character: marine MTB is distinct from freshwater MTB, and off coast MTB are remotely related with ocean MTB. In contrast, the MTB from similar habitats, such as offshore in Brazil and the United States or freshwater lakes in Germany and China, are closely related. It is found that similar species have a large geographic distribution and tend to adopt the similar habitats, morphotypes of MTB and their living environment conditions have a significant relevance. This observation suggests that MTB may have multiple evolutionary origins. And also, it suggests the environmental conditions, as an important evolutionary pressure, play an important role in the long-term evolution of MTB.