eLife assessment
This important study combines experiments and fluid mechanics modeling to determine the mechanism of the ultrafast ejection of the polar tube of the Microsporidia parasite and of transport through this tube. The methods and the analysis, based on the variation of the viscosity of the external medium, are compelling and allow for the first time to discriminate among proposed ejection mechanisms. This approach where simple physical principles are used for distinguishing between mechanisms when the precise geometry is inaccessible through imaging is potentially applicable to other systems in microbiology.