268 



INTRACELLULAR LUMINESCENCE 



At a given temperature, the composition of the medium, both with 

 respect to inorganic salts and nutrient constituents, can also pro- 

 foundly modify the expression of genetic potentialities for lumines- 

 cence. With minimal amounts (about 0.5%) of NaCl to permit growth 

 of A. fischeri in nutrient broth, no visible luminescence occurs (War- 

 ren, 1945; Johnson, 1947; Farghaly, 1950), although subcultures in 

 approximately isotonic (3%) NaCl luminesce normally. Complicated 



140- 



A 



LUMINESCENCE 



J \ \ L 



GROWTH-—, 



U- LUMINESCENCE 



i I \ L 



20 



100 



SO 



60 



40 



20 



TIME (hours) 



Fig. 3. Rate of growth and of increase in luminescence intensity of A. fischeri 

 on a basal medium consisting of inorganic salts plus glycerol (A), and on 

 the same medium with the addition of 3 micrograms of methionine per ml 

 (B). The points on the ordinate are expressed in terms of per cent, with 

 the highest value of luminescence and the corresponding amount of growth 

 on the basal medium without the added methionine arbitrarily taken as 

 100%. (After Farghaly, 1950.) 



relationships have been observed between the luminescence of cul- 

 tures and the types as well as concentrations of salts in the medium 

 (reviewed by Harvey, 1940, 1952). The same is true of specific nutri- 

 tive substances, as shown in quantitative studies by Farghaly (1950); 

 for example, the addition of small amounts of methionine to a basic 

 medium practically eliminates the lag in light production as com- 

 pared to growth ( Fig. 3 ) . 



Among different species of luminous bacteria, the maximum bright- 



