Lumisomes, the Cellular Site of Bioluminescence in Coelenterates

Abstract From ten species of bioluminescent coelenterates we have isolated a membrane-enclosed subcellular particle that is apparently responsible for the bioluminescence in these animals. The animals investigated were species of Obelia and Clytia (from the class Hydrozoa) and species of Renilla, Ptilosarcus, Stylatula, Acanthoptilum, and Parazoanthus (from the class Anthozoa). By electron microscopy the purified particle preparations appear quite homogeneous in size and shape, have a diameter of approximately 0.2 µm, and are enclosed by a unit membrane. The particles contain all of the proteins necessary for producing the typical green bioluminescence (λmax 509 nm) observed in vivo in these animals. These include luciferase, a calcium-triggered photoprotein and a green fluorescent protein. Bioluminescence is evoked from the particles when they are placed in hypotonic solutions of calcium ion. Oxygen is also required for light emission. The color of the light is green, typical of the observed in vivo emissions. The widespread occurrence of these bioluminescent particles among the coelenterates suggest that they represent the cellular site of bioluminescence in these animals. We propose that these subcellular bioluminescent particles or organelles be referred to as lumisomes.