1College of Science and Engineering, Kanazawa University
Magnetotactic bacteria (MTB) are ubiquitous Gram-negative bacteria and represent a morphologically, phylogenetically, and physiologically diverse group. MTB have intracellular organelles which comprise nano-sized magnetite/greigite crystals and various kinds of proteins surrounded by a phospholipid bilayer. We call these organelles as magnetosomes. The magnetosomes have well-ordered chain-like structures and function as a cellular compass to navigate along the Earth’s magnetic field. MTB are phylogenetically diverse with members across the Proteobacteria, Nitrospirae and Candidate division OP3. Most MTB in the Proteobacteria phylum belong to the Alpha- and Deltaproteobacteria classes. Recently we have found novel MTB which are unusually large (~13 by ~8 micro-m). It swims in a helical trajectory toward the south pole of a bar magnet by means of a polar bundle of flagella. Phylogenetic analysis based on the 16S rRNA gene sequence revealed that they belong to the Gammaproteobacteria and represent a new genus of magnetotactic bacteria. In this meeting we will introduce the method to collect MTB from the natural environments and report the diversity and discuss the evolution, especially, a common ancestor to all MTB. It should be noted that Lefevre et al. proposed the common ancestor of all Proteobacteria to be magnetotactic (Environ Microbiol. 2013,15:2267-74).