Analysis of the behavior of a well-designed artificial gene network may provide insights into the underlying mechanisms of gene regulation mechanisms and dynamics of natural systems. In the present work we are interested in examining the role of gene network structure of modified lacP/O systems on gene expression patterns, particularly the degree of heterogeneity within a population as indicated by a reporter protein. Specifically, we are designing and constructing negative feedback gene regulatory systems by placing the gene encoding the green fluorescent protein (gfp), which serves as a reporter, and the gene encoding the LacI repressor protein under the control of the same or different O_lac promoter systems in Escherichia coli. We will monitor the GFP expression at the single cell level by a flow cytometer. Results from shake flask as well as chemostat experiments of strains carrying various genetic constructs will be presented and discussed.