Exploration of the biodiversity of magnetotactic bacteria – BIOMAGNET

During the course of evolution, environmental changes deeply modified ecosystems in which microbial communities rapidly adapted. To predict the impact ecosystems have on bacterial biodiversity requires both to follow evolutionary history of valued functions/traits in different ecosystems and to obtain molecular data on microbial adaptation to changing environmental pressures. Combining in situ, in vitro and in silico approaches, I propose here to use magnetotactic bacteria (MTB) as models to investigate the evolutionary dynamics of a prokaryotic organelle, from the genome to the phenotype and from its ancestral emergence to its present function into easily disturbed habitats. Indeed, MTB are motile aquatic prokaryotes whose swimming direction is guided by magnetic fields, including the Earth’s geomagnetic field. This behavior, named magnetotaxis, is due to the synthesis within the MTB cells of magnetosomes which are constituted of a biomineralized magnetic crystal, composed of either an iron oxide (magnetite Fe3O4) or iron sulfide (greigite Fe3S4), surrounded by a lipid bilayer magnetosome membrane. Generally found at the oxycline (oxic-anoxic interface) in sediments of aquatic environments, these highly diverse, easy-to-observe prokaryotes represent unique models to understand the genetic basis of phenotypic diversity and plasticity organisms developed for optimal adaptation in specific biotopes.
My project is driven by the hypotheses of an underestimation of MTB biodiversity and their monophyletic evolution. By studying their evolutionary history, this challenging proposal aims at demonstrating the important past and present role of MTB in aquatic environments.
The main objectives of this project are i) to infer the ancestral role of magnetosomes, ii) to understand how the ancestor of MTB adapted during the course of evolution to give rise to the magnetosomes and iii) to address how the different MTB of the present acquired the ability to be magnetotactic. At the issue of this project, I will not only decipher the origin and evolution of magnetotaxis but I will also provide new data on the biogeography of MTB and new knowledge on the environmental and genetic factors involved in the formation of magnetosomes. Moreover, with the cultivation of new MTB species, we will dispose of novel magnetotactic models for the development of fundamental or applied researches in physics, chemistry, geology, biology and biotechnology.