“….& Some& bacterial& species& can& produce& extracellular& polymeric& substances&(EPS),&which&improve&a&soil's&moisture&retention&and&act&to&aggregate&soil&particles& together,& further& altering& underground& hydrodynamics 12,13 .& Thus,& bacterial& characteristics& are& tightly& coupled& with& the& dynamics& of& soil& conditions.& This& bacteria=soil& interplay& has& implications&for&bioremediation,&water&quality,&nutrient&cycling,&and&underground&ecology.&It&is& therefore& necessary& to& study& soil& bacteria& within& the& structural& and& hydrodynamic& context& of& their& natural& environment& and& on& length& scales& appropriate& to& cellular& functions& (i.e.& the& pore& scale)&to&elicit&emergent&behaviours.&Unfortunately,&the&opacity&of&soil&presents&a&challenge&for& the&direct&visualization&and&measurement&of&bacterial&traits&at&the&pore=scale&in#situ.& Experiments& in& sand& columns& and& micromodels& have& enabled& measurements& of& bulk& bacterial&transport&through&porous&media&and&have&even&allowed&some&preliminary&imaging&of& bacteria& in& pore=spaces [14][15][16][17] .& Nafion,& a& transparent& fluoropolymer& that& is& sometimes& used& as& a& sand& substitute,& can& further& increase& the& imaging& compatibility& of& bacteria& in& flow& cells 18,19 .& However,&these&systems&do¬&have&a&defined&structure&and&are&often&treated&as&'black&boxes',& making&it&impossible&to&correlate&pore=scale&hydrodynamics&with&bacterial&biofilm&distribution.&& In& other& synthetic& systems,& microfluidic& platforms& have& been& used& to& visualize& bacterial& behaviour& in& flow& through& narrow& channels& and& around& tight& corners 20,21,22 .& These& platforms& reduce& the& physicochemical& complexity& of& natural& porous& media& while& testing& bacterial& characteristics&in&highly¶meterized&and&fully&defined&systems 23 .&&Microfluidic&systems&have& the& added& benefit& of& retaining& the& same& physical& structure& for& each& experimental& replicate,& allowing& flow& in& the& channels& to& be& computationally& simulated 24,25 .&a...…”