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Lumazine protein is a member of the riboflavin synthase superfamily and the intense fluorescence is caused by non-covalently bound to 6,7-dimethyl 8-ribityllumazine. The pRFN4 plasmid, which contains the riboflavin synthesis genes from <i>Bacillus subtilis</i>, was originally designed for overproduction of the fluorescent ligand of 6,7-dimethyl 8-ribityllumazine. To provide the basis for a biosensor based on the <i>lux</i> gene from bioluminescent bacteria of <i>Photobacterium leiognathi</i>, the gene coding for N-terminal domain half of the lumazine protein extending to amino acid 112 (N-LumP) and the gene for whole lumazine protein (W-LumP) from <i>P. leiognathi</i> were introduced by polymerase chain reaction (PCR) and ligated into pRFN4 vector, to construct the recombinant plasmids of N-<i>lum</i>P-pRFN4 and W-<i>lum</i>P-pRFN4 as well as their modified plasmids by insertion of the <i>lux</i> promoter. The expression of the genes in the recombinant plasmids was checked in various <i>Escherichia coli</i> strains, and the fluorescence intensity in <i>Escherichia coli</i> 43R can even be observed in a single cell. These results concerning the co-expression of the genes coding for lumazine protein and for riboflavin synthesis raise the possibility to generate fluorescent bacteria which can be used in the field of bio-imaging.