Inhibition of bioluminescence in Photobacterium phosphoreum by sulfamethizole and its stimulation by thymine

In bioluminescent bacteria very few agents have been reported that can selectively inhibit the luminescence. In sensitivity tests with Photobacterium phosphoreum, using 55 different antibiotics, it was found that sulfamethizole, an inhibitor of dihydropteroate synthetase and the formation of folic acid, inhibited bioluminescence more than growth. Likewise, in mutants requiring thymine for growth, the luminescence per cell was much less in a medium low in thymine. In neither case could the decreased specific luminescence be attributed to a decrease in the cellular level of luciferase or aldehyde factor; the involvement of additional but unidentified factors in the regulation of in vivo bioluminescence is postulated.