Visualization of Bioluminescence

There are an increasing number of specialized instruments that may be used for the purpose of measuring bioluminescence. Table 1 contains a representative list of different luminometers and cameras that are available. These instruments have been used to detect bioluminescence in a number of organisms using either bacterial luciferase (lux ; 1 , 2 ) or firefly luciferase (luc ; 3 , 4 ) as reporters. Sensitivity of the newer luminometers ranges from six to eight logs. Options such as temperature control and agitation of samples are usually available at an extra cost. Most of the systems can be driven by computer with commercially available or customized software. Storage, display, and analysis of data involve the same or additional software packages. Sample containers have also become more specialized. In the case of the multiplate luminometers, opaque plates are available in either white or black. Black plates are recommended for bright samples where reflection into neighboring wells results in “crosstalk.” White plates are recommended for samples that are lower light emitters, since the reflective surface enhances detection. Opaque plates are also available with transparent bottoms. Samples in these microplates may be read in a spectrophotometer (such as an ELISA reader) to measure optical density of the sample, as an indicator of cell number particularly in the case of bacterial cells. In some applications, opaque microplates containing samples may be stacked in alternation with transparent microplates, if samples require a light source. This is essential for many of the studies involving photosynthetic microorganisms (5 , 6 ) as well as for those studying circadian rhythms for which light entrainment is needed (5 –7 ). Table 1  Commercial Luminometers, Listed by Sample Format

a Single sample b Multlple sample c Not all are CCD cameras