BIOLUMINESCENCE: BIOCHEMICAL AND PHYSIOLOGICAL ADVANCES

Abstract

Bioluminescent organisms are to be found among the bacteria, fungi, unicellular algae, and most of the major animal phyla, some of which contain hundreds of luminescent species. Early biochemical studies reflected this taxonomic diversity and often a primary focus of attention was the uniqueness of each newly isolated system. Relatively few in vitro cross‐reactions were discovered among unrelated species and five of the first six luciferins to be characterized proved to be structurally unrelated compounds. The functions of bioluminescence in many organisms were unknown and, while several theories arose, these theories seldom addressed the part that light production might play in the ecology of an organism or a population. Major advances on each of these fronts have been made during the past decade. Biochemical research has centered on the chemical mechanism(s) of luminescence and a single type of chemical species, a dioxetanone, has emerged as a common intermediate in several (but not all) bioluminescence and chemiluminescence systems. Likewise, in the last 10 years, numerous interphyletic cross‐reactions have been discovered and the ecological functions of bioluminescence for a large number of species have been established. Intensive studies are continuing on reaction mechanisms, especially those involving the bioluminescent bacteria, and much remains to be learned about the protein biochemistry of all luminescence systems. Amino acid sequence determinations and X‐ray crystallographic studies have been initiated in several laboratories and, in others, attempts are being made to clone the genes that code for bioluminescence proteins. Sensitized bioluminescence has been implicated in representatives of both prokaryotic and eukaryotic organisms. Low level biological chemiluminescence has been investigated in a variety of systems including liver microsomes and phagocytic leucocytes using sensitive photon counting devices. Perhaps the area of greatest growth, however, has been the application of bioluminescence and chemiluminescence techniques as tools of clinical research. The need for safe, sensitive and specific assay methods has, for example, stimulated the development of immobilized luciferases and luciferase‐linked enzyme systems. In addition, luminescence immunoassay has emerged as a reasonable alternative to the commonly used, but more troublesome, method of radioimmunoassay. This trend toward applications development has shifted the emphasis of some of the university laboratories and in general has improved the lines of communication between basic and applied research groups working in the area of bioluminescence.