Iron represses bioluminescence and affects catabolite repression of luminescence inVibrio harveyi

Bioluminescence and the synthesis of luciferase inVibrio harveyi growing in a minimal medium are repressible by iron; this is not significantly reversed by cyclic adenosine 3,5-monophosphate (cAMP). Cultures grown with added iron emit less light and possess less luciferase per cell than those grown under conditions of limiting iron; this may have significance in relation to the function of luciferase as an electron carrier. With iron, and with glycerol as the sole carbon and energy source, the addition of glucose causes further repression, both transient and permanent, and this is only partially reversible by cAMP. Without iron, glucose addition results in only a small and transient repression, but this is fully reversible by cAMP. The inability of cAMP to reverse iron-influenced repression may be explained by both a low rate of transport of cAMP into the bacteria and increased intracellular levels of cyclic nucleotide phosphodiesterase.