The present invention relates to growing and testing microorganisms in a multitest format which utilizes a gel forming matrix for the rapid screening of clinical and environmental cultures. The present invention is suited for the characterization of commonly encountered microorganisms (e.g., E. coli, S. aureus, etc.), as well as commercially and industrially important organisms from various and diverse environments (e.g., the present invention is particularly suited for the growth and characterization of the actinomycetes and fungi). The present invention is also particularly suited for comparative analysis of phenotypic differences between cell types, including strains of microorganisms that have been designated as the same genus and species, as well as other cell types (e.g., mammalian, insect, and plant cells).