Reddish Escherichia coli Cells Caused by Overproduction of Bacillus stearothermophilus Uroporphyrinogen III Methylase

During shotgun cloning of an amylase gene, we found a transformant of Escherichia coli with a reddish color. The transformant produced highly water-soluble red pigments the molecular masses of which were less than 3000. The plasmid harbored by the transformant contained a DNA fragment derived from a strain of Bacillus stearothermophilus. Truncation of the insert DNA showed that an 1. 1-kbp Sau 3A-SalI fragment was responsible for the reddish colony. An open reading frame was found in the nucleotide sequence of the 1. 1-kbp DNA fragment. The production of the red pigment was accompanied by a colorless 28-kDa protein. The sequence of the 28-kDa protein was highly homologous to bacterial uroporphyrinogen III methylases participating in corrinoid biosynthesis. The 28-kDa protein was found to be a thermostable uroporphyrinogen III methylase.