Rapid clonal growth measurements at the single-cell level: gel microdroplets and flow cytometry

We describe a new, general method for rapidly measuring clonal growth of large numbers of individual members of a cell population. This method is based on microculture of individual colony-forming units in gel microdrops (GMDs; here agarose; 20 to 90 mu in diameter), which are sufficiently robust to be handled much like cells, and diffusionally transparent for molecules of interest. Flow cytometry provides rapid measurements of GMD-entrapped microcolonies, and permits subpopulation analysis. Here the method is demonstrated with mammalian, fungal and bacterial species. Additional results illustrate rapid determination of a drug-resistant subpopulation in a mixed species sample, and nutrient sensitivity for a murine hybridoma.