BIOLUMINESCENCE WITH SULFANILAMIDE AND URETHANE 



511 



Table 10-2 



Effects of Sulfanilamide and Urethane on Bacterial Luminescence at 

 Different Temperatures " 



Temp. 

 (°C) 



15 



20 

 25 

 30 

 35 



% Inhibition 



Sulfanil- 

 amide 



Ure- 

 thane 



Both 



Vibrio phosphorescens 



Photobacterium phosphoreum 



I ° ° § 



2 -2.2 -J 



I— I o 1^ g 



79.8 

 75.8 

 72.7 

 79.9 

 84.0 



" Data from Johnson et al. (1943). Iq is the intensity of luminescence in the absence 

 of inhibitors, I^ with sulfanilamide, !„ with urethane, and Is+„ with both inhibitors. 

 Concentrations: sulfanilamide, 3 m3I and urethane, 150 mM. The per cent inhibitions 

 calculated in the last column using the equation is+„ = ig + i„ — ij^. The urethane 

 concentration was 75 milf in the Photobacterium esxperiment. 



It is stated by Johnson et al. (1943) that antagonism, no effect, and syn- 

 ergism are all observed depending on the temperature. Their definitions 

 of these terms are quite different than those adopted above, since they 

 use "antagonism" to designate cases in which the combined inhibition is 

 lower than that of either inhibitor alone, "no effect" to indicate a com- 

 bined inhibition of the same magnitude as that of either inhibitor alone, 

 and "synergism" to indicate a greater combined inhibition than with ei- 

 ther inhibitor alone. It may be seen, however, in every case that the pres- 

 ence of one inhibitor reduces the inhibition produced by the other inhi- 

 bitor and it seems to the author that this would justify classifying the in- 

 teraction here as antagonism. 



It is interesting that the degree of antagonism varies markedly with 

 the temperature, especially in Vibrio where at 15° the inhibition by the sul- 

 fanilamide is almost completely counteracted while at 35° the situation 



