Molecular mechanisms of bacterial magneto-aerotaxis

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Magnetotactic bacteria (MTB) possess the unique ability to navigate using the Earth’s magnetic field. Magnetic navigation results from the passive magnetic alignment of cells based on the synthesis of magnetosomes, intracellular membrane-enveloped crystals of a magnetic iron mineral arranged in chains, and active motility utilizing flagella. Magnetic alignment is believed to facilitate orientation within aquatic habitats towards growth-favoring oxygen concentrations, a behavior known as magneto-aerotaxis. However, the molecular mechanisms controlling this unique motility pattern, which differs significantly from those of well-studied model organisms like Escherichia coli, are poorly understood. In particular, it is unknown if and how the perception of magnetic fields and oxygen gradients is integrated via the complex chemosensory network in MTB to control flagellar motor output. To study the molecular mechanisms of bacterial magneto-aerotaxis, I established fluorescent labeling of flagella in the genetically tractable polarly flagellated MTB Magnetospirillum gryphiswaldense. In the proposed project, this method will be used to determine how the chemosensory system coordinates flagellar motors in magnetospirilla - a question that has not been solved and for which contradicting models have been postulated (including non-magnetic bipolarly flagellated spirilla), such as the rotation of opposing flagellar motors in opposite senses, in the same direction, or pausing of motors. Additional aims will be to unravel how environmental signals and parameters (such as the oxygen gradient, the ambient magnetic field, or the environmental structure) affect flagellar motor output, polar assembly of flagella, and directional motility in magnetic fields (so-called North-/South-seeking magneto-aerotaxis). Ultimately, this project will yield a breakthrough in the understanding of the molecular principles that govern magnetic navigation in bacteria. Expected findings will also have broader implications related to bacterial motility and microbial cell biology, such as complex bacterial signal transduction systems, flagellar assembly and motor control in polar flagellates (including many clinically relevant pathogens), and how population heterogeneity and different motility patterns relate to the selective advantage in complex environments. Finally, a comprehensive understanding of magneto-aerotaxis may open the door for future applications in synthetic biology, such as the targeted modification of MTB and the engineering of magnetic navigation for microrobotic applications.