Magnetotactic bacteria (MTB) navigate along Earth’s magnetic field. We hypothesize that magnetic alignment modulates dispersion in sediments, thereby promoting MTB biodiversity in heterogeneous environments. We will recast microbial colonization as a problem in extreme-value statistical physics: the key quantity is not the mean, but the arrival of the first bacterium that seeds a colony. Experimentally, we will quantify transport and rare-event statistics by combining microfluidic sediment analogs, optical tracking, and magnetically controlled flow/field conditions, supported by a complete microfluidic platform (microfabrication and microscopy). Theoretically, we have developed a full simulation pipeline. Together, these approaches will link heterogeneities in pores, flows, and bacterial traits to population-level dispersion and segregation.