Magnetosome Gene Duplication as an Important Driver in the Evolution of Magnetotaxis in the .

The evolution of microbial magnetoreception (or magnetotaxis) is of great interest in the fields of microbiology, evolutionary biology, biophysics, geomicrobiology, and geochemistry. Current genomic data from magnetotactic bacteria (MTB), the only prokaryotes known to be capable of sensing the Earth's geomagnetic field, suggests an ancient origin of magnetotaxis in the domain Vertical inheritance, followed by multiple independent magnetosome gene cluster loss, is considered to be one of the major forces that drove the evolution of magnetotaxis at or above the class or phylum level, although the evolutionary trajectories at lower taxonomic ranks (e.g., within the class level) remain largely unstudied. Here we report the isolation, cultivation, and sequencing of a novel magnetotactic spirillum belonging to the genus ( sp. strain SH-1) within the class The complete genome sequence of sp. strain SH-1 revealed an unexpected duplication event of magnetosome genes within the operon, a group of genes essential for magnetosome biomineralization and magnetotaxis. Intriguingly, further comparative genomic analysis suggests that the duplication of genes is a common feature in the genomes of alphaproteobacterial MTB. Taken together, with the additional finding that gene duplication appears to have also occurred in some magnetotactic members of the , our results indicate that gene duplication plays an important role in the evolution of magnetotaxis in the and perhaps the domain A diversity of organisms can sense the geomagnetic field for the purpose of navigation. Magnetotactic bacteria are the most primitive magnetism-sensing organisms known thus far and represent an excellent model system for the study of the origin, evolution, and mechanism of microbial magnetoreception (or magnetotaxis). The present study is the first report focused on magnetosome gene cluster duplication in the , which suggests the important role of gene duplication in the evolution of magnetotaxis in the and perhaps the domain A novel scenario for the evolution of magnetotaxis in the is proposed and may provide new insights into evolution of magnetoreception of higher species.