Flow cytometric analysis of entire microbial colonies

Much could be gained if the scope of flow cytometry could be broadened to the study of entire cell colonies, rather than to populations of single, separate cells. This can be achieved by encapsulating single microbial cells in small spheres in a way that allows each cell to multiply and form a colony within its respective microbead, which is then amenable to analysis by flow cytometry. Methods for performing the encapsulation within beads of appropriate size and homogeneity have been developed (Nir et al., Appl. Environ. Microbiol. 56:2870-2875, 1990). We describe here how a variety of properties of the entrapped colonies, such as mass, growth rate, enzymatic activity, and expression of specific antigens, can be measured, and we discuss how these constructs can be utilized to select microbial mutants.