Measuring mutations with droplet microfluidics*

Mutations are random errors in genetic material that create the diversity which underpins the development of all life. However, work done over recent years has suggested that certain mutations are not as random as once thought - several factors such as stress, chromosomal neighborhood, and transcription level have been implicated to affect genetic stability. Typically, quantitative measures of frequency and distribution of point mutations have either relied on fluctuation tests that make assumptions about the shape of mutation distributions, or on large volumes of data from multiple sources that can harbor unknown inconsistencies. We use a droplet-based, microfluidic platform to make real-time measurements of point mutations in bacteria under various conditions with high precision. We are able to alter various conditions of growth, such as heat/drug stress and transcriptional activity, and detect mutations without the use of a selective or metabolic screen, which makes our system a versatile tool for studying mutant occurrence. Our results offer a direct look into this often-simplified area of evolutionary dynamics.