Bacteria can thin liquids to make them fall more easy . surprisingly , they can do this to the point where the liquid they are swimming in becomes asuperfluid , something with zeroviscosity – a phenomenon antecedently only witnessed under uttermost condition , such as temperature close toabsolute zero .
For the field , Dr. Harold Auradou of the University of Paris - Sud addedE. colito liquids in different concentrations . To ensure the bacterium focused on swim , he put in enough nutrient to keep them animated , but not enough to charm them to reproduce . Each solution was then spin in arheometerto measure how the concentration of bacteria affected the power of the liquid to flow .
The result was something like what physicist see as they test electric electric resistance whencooling metals and sure ceramic . At first , mount concentrations of bacterium caused a steady reduction in viscosity , allowing the liquidness to run more freely . This is in keeping withmodelling done in 2009on how elongated lifeforms , propelling themselves using tiny flagellum , would mold the liquid in which they float .
However , just as fall electric resistance cansuddenly drib to zero , Auradou describe inPhysical Review Lettersthat in some circumstances all traces of shear opposition vanishes . In other words , the liquidness do in a personal manner similar to liquid helium below -271 ° C ( -456 ° F ) , whoseparty trick behaviordazzles the judgement .
“ If you utilize beat bacteria , nothing changes , ” Auradoutold Nature , which demonstrates the effect is a map of the swimming behavior , rather than the bacteria ’s shape . Indeed , while all strains ofE. coliproduced very low viscosity at concentrations between 0.6 % and 2.4 % by intensity , it is only the most actively swim strains that change state the solution in which they move into a superfluid .
Nevertheless , Auradou does not claim to know how zero viscousness is achieved . “ We believe that there is a kind of collective motion of the bacterium that we do n’t infer yet , ” hesaid . Almost certainly , thetail - like flagellahave something to do with it . glutinous condition make swimming hard for the diminutive bacteria , obstructing them from reaching their intellectual nourishment , so the flagella have evolved to interrupt the force between molecule that are one of theroot causes of viscosity .
Auradou ’s discovery required the use of equipment generally reckon obsolete . modernistic rheometers “ are made to value high viscousness and higher shear rate , ” Auradousays , and could n’t go after resistance this low . combine an old rheometer with modern computing machine controls created a machine capable of distinguishing between grim and zero viscosity .
At the here and now , this is basic enquiry without direct practical app , but Auradou suggests it could test utilitarian in the production of tiny motors .
