Controlling Morphology of Aerotactic Bacterial Bands*

Microorganisms have perfected numerous evolutionary adaptations to improve their odds of survival and proliferation. This study exploits some of these adaptations such as flagellated swimming, aerotaxis and magnetotaxis in magnetic bacteria (MTB) to reshape entire swarms of them. These microorganisms have specialized strategies to navigate oxygen landscapes, of which perhaps the most intriguing is the biomineralization of magnetic nanocrystals that are thought to help them align with the geomagnetic field (magnetotaxis) and swim along natural oxygen gradients. Resulting migration to oxic-anoxic transition zones (OATZ) leads to aerotactic band formation. Many bacteria achieve motility through spinning helical flagellar appendages that produce flow fields that are well described in the far field by analytical models. However near-field dynamics remain elusive. We utilize lattice Boltzmann-based numerical models to simulate near field hydrodynamic interactions, metabolism-dependent oxygen diffusion in the medium, aerotactic response of the cells, as well as field controlled magnetotaxis. Strategies to achieve swarm morphologies beyond simple MTB aerotactic bands will be discussed.