Characterization of a gene conferring red fluorescence isolated from an environmental DNA library constructed from soil bacteria.

A gene (cob) conferring red fluorescence on Escherichia coli cells was isolated from an environmental DNA library constructed from soil bacteria. The nucleotide sequence showed a single open reading frame (ORF) encoding a polypeptide of 257 amino acid residues responsible for the red fluorescence. The deduced amino acid sequence of the ORF showed significant similarity (less than 75% identity) to uroporphyrinogen III methyltransferases from various bacteria. Cell extracts from the E. coli transformant had a spectrum pattern of fluorescence corresponding to trimethylpyrrocorphin or sirohydrochlorin that was absent in the control cells harboring the vector alone. Expression of the cob gene in the fungus Fusarium oxysporum conferred red fluorescence on the host cells, indicating that it is a promising transcriptional reporter in fungi as well as bacteria.