Spatial segregation during oxytaxis-driven bioconvection in multispecies planktonic bacterial communities

Joel Stavans, Professor at Department of Physics of Complex Systems, Weizmann Institute of Science, Israel

Large groups of agents often exhibit self-organized, collective motion and the emergence of coherent spatial structures whose characteristic scales largely exceed the size of the agents themselves. Prime examples covering many length scales range from mammal herds, fish schools and bird flocks, to insect and robot swarms. Despite significant advances in understanding the behavior of large homogeneous groups in the last decades, little is known about the self-organization and dynamics of heterogeneous groups.

Under oxygen gradients, oxytactic (aerotactic) motile bacteria can swim in auto-organized, flows called bioconvection, whose spatial scales exceed the bacterial size by three orders of magnitude. I will present results of bioconvection experiments with multispecies suspensions of wild-type bacteria collected from the hyper-diverse bacterial communities of Cuatro Ciénegas in Mexico, whose origin date to the pre-Cambrian. Our real time fluorescence microscopy experiments show that these bacteria display a plethora of amazing dynamical behaviors, including inter-species spatial segregation in shallow suspensions. The mechanisms giving rise to these complex behaviors stem both from biological and physical inter-species interactions.

The results advance our understanding of heterogeneity in the dynamics of complex planktonic microbial ecological communities and the role of oxygen in the water column, bringing profound insights into their spatial organization and collective behavior.