Escherichia coli is a very diverse bacterial species. Bacterial strains with genes for virulence factors provoke infections. For commensal and pathogenic strains, adhesins are essential for first contact with the host, they also have systems for iron uptake and to avoid the host’s immune system. Pathogenic strains, harbor genes for toxins that damage host cells. In populations of genetically identical bacterial cells, phenotypic heterogeneity has been described. Heterogeneous gene expression provides bacteria an advantage in variable environments and under stress conditions. The purpose of our study was to construct gene fusions of promoters of some virulence factor genes and genes for fluorescent proteins and subsequently analyze their expression with fluorescence microscopy. We studied promoters of genes, clbA for phosphopanteteinyl transferase, cnf1 for toxin Cnf1, and cdtABC for cytoxin CDT. Gene fusions were prepared stepwise in the plasmid vector pBAC and introduced into the bacterial strain MG1655. We found that all cells expressed the clbA gene. Expression of genes for the Cnf1 toxin and cytotoxin CDT was heterogeneous, as they were expressed in only a small subpopulation.