Collective bacterial vision

Bacteria are well studied primitive organisms and an ideal system for physical scientists to study how simple systems perform complex tasks. Swarming is one such complex collective phenomenon of producing surfactant to ease their motility on a semi solid surface (nutrient supplemented 0.6% agar). We perturbed the swarming pattern of Pseudomonas aeruginosa (PA) by incorporating inert obstacles (PDMS) in the agar plate thus creating local depletion of nutrient and water rich agar surface. To our surprise, we noticed that the bacteria as they colonize the surfaces with such obstacles effectively avoid them by changing the course of their path at a distance as far as 5 mm thus ‘seeing’ (sensing) them at ∼ thousand body lengths. We refer to this phenomenon as “collective bacterial vision”. We demonstrate a fluid dynamic model that can guide them around these obstacles. Our model leads to further questions such as, is it possible for a single bacterium to possess “bacterial vision”? What is the grouping cost and ideal group size? Is there a need for information transfer in the group? Is this phenomenon a completely active or completely passive or a delicate balance between them? We will describe our attempts to address some of the above questions though most of them are still open.