Movement analysis of the bilophotrichous magnetotactic bacteriaMagnetofaba australisstrain IT-1

Magnetotactic bacteria (MTB) are microorganisms that biomineralize intracellular magnetic nanoparticles inside a membrane vesicle/invagination. The set membrana + magnetic nanoparticle is known as magnetosome and generally magnetosomes are organized in linear chains in the cytoplasm, conferring a magnetic moment to the MTB. Due to their magnetic properties, MTB swim by following local magnetic field lines. This property makes MTB a suitable model to study bacterial movement. There are theoretical models to analyze the swimming of MTB, but the majority consider monotrichous bacteria. Only one model is related to the swimming of bilophotrichous bacteria, but they do not report the resultant trajectory parameters as a function of the magnetic field. Also, the literature lacks an experimental analysis of the trajectories of bilophotrichous MTB. The present study analyzes the movement of the bilphotrichous MTBMagnetofaba australisstrain IT-1 exposed to different magnetic field intensities. The trajectories are composed of two oscillations, one of low frequency and large amplitude and another of high frequency and small amplitude. The amplitudes show a magnetic field dependency, and the frequencies show to be magnetic field independent. The analysis of the trajectory orientation relative to the magnetic field direction shows that magnetotaxis ofM. australisfor low magnetic fields is not as efficient as expected, perhaps due to living in a liquid culture medium rich in nutrients. As far as we know, this is the first time that these movement data have been obtained, and they will be important to validate future theoretical models of movement for bilophotrichous MTB.