BERNARD L. STREHLER 223 



chemistry of the ten strains of luminous bacteria which have been 

 examined in vitro (Cormier and Strehler, 1954). Identical require- 

 ments were found for luminescence in terms of diffusible factors 

 among all these strains, e.g., reduced DPN, FMN, and long-chain 

 aldehydes are necessary for the luminescence of their extracts. Cer- 

 tain striking differences were also obvious. These included a wide 

 variation in apparent Michaehs constants and a considerable range of 

 temperature optima and temperature dependences (apparent activa- 

 tion energies ) for the luminous reaction. 



Inasmuch as there was a great diversity in the morphology of the 

 organisms studied and in the luminescence per unit dry weight of 

 acetonized powders (whose luminescence yield paralleled the in vivo 

 brightness of the strains ) , it would seem unlikely that they are closely 

 related to each other evolutionarily. On the other hand, the identical 

 biochemical requirements for extract luminescence indicate that the 

 mechanism operating in the various strains is probably identical. These 

 differences and similarities can all be accounted for if one assumes 

 that the luminescent pathway in all the luminescent bacteria studied 

 is derived from a normal respiratory pathway (Harvey, 1940). The 

 ability to produce light, then, can be visualized, as arising from a 

 special mutation in a flavin auto-oxidase pathway, permitting the 

 energy liberated on the oxidation of one or more flavins to be lib- 



