Fig. 4.

Schematic illustration of the magnetotactic consortium showing the magnetotactic behaviour in the Northern Hemisphere and the syntrophic interactions between partners. The green arrows show the anterior–posterior orientation of the organisms, which is parallel and antiparallel to the Earth’s magnetic field lines for the freeliving magnetotactic bacteria (MTB) and the consortium protist-MEB, respectively. The purple arrows show the organism’s motility zone in the sediments. The ATP synthesis by the hydrogenosomes in the protist is symbolized by the blue arrows. Molecular hydrogen, acetate and carbon dioxide are products that could be transported through the plasma and used by the MEB as sources of energy and carbon. The red arrows show the dissimilatory sulfate reduction by MEB, which uses hydrogen as an electron donor and produces hydrogen sulfide outside the consortium. OATZ, oxic–anoxic transition zone.