Isolation, identification, and function of long chain fatty aldehydes affecting the bacterial luciferin-luciferase reaction.

Although luminous bacteria are among the most accessible of light-producing organisms, until recently attempts to obtain the light-producing reaction in vitro have been unsuccessful. Owing partly to the development of ultrasensitive light-detecting apparatus such as the quantum counter (l), it has been possible in our laboratory to develop procedures required to obtain a sustained bright luminescence from extracts of the luminous bacterium Achromobacter jischeri and from the other nine strains of luminous bacteria tested (2). Since it was a simple matter to detect the minimal luminescence emitted when an acetonized powder from luminous bacteria was suspended in water, a systematic investigation of the effect of various physical and chemical factors soon led to the experimental production of a bright luminescence. Initially, we found that DPNl or its reduced homologue was a factor which first became limiting for luminescence (3). Subsequently (4), a,t least two other factors were found to be necessary for optimal luminescence. One of these compounds is FMN; the other is a factor from hog kidney cortex which we have termed KCF. McElroy and coworkers have confirmed the finding of a DPNH, requirement for luminescence and they have also observed a requirement for FMN (5, 6). In addition, they observed that another factor obtained from the bacteria which they have considered analogous to firefly luciferin (7, 8) is necessary for luminescence. Their basis for this terminology was, by analogy to the inactivation of firefly luciferin, apparently the destruction of this heat-stable factor during luminescence. It is not at present clear whether this loss of activity is dependent on light emission or merely on removal by an unknown enzymatic action in the bacterial extracts. Recently, we have reported in preliminary form (9) the identification of