FRANK H. JOHNSON 291 



Although extensive studies concerning the action of inhibitors on 

 the luminescence of bacterial extracts have not been undertaken as 

 yet, exploratory experiments with the saturated system have yielded 

 some interesting results. Thus, sulfanilamide reduces the steady-state 

 level of luminescence, and the amount of inhibition at a given con- 

 centration of the drug decreases with rise in temperature, whereas it 

 is only slightly affected with rise in pressure, as in cells. The actual 

 concentration required for a given per cent inhibition in extracts of 

 A. fischeri, however, is many times higher than that required in cells 

 of this species, possibly because of the presence, in these extracts, of 

 large amounts of inert material on which the sulfanilamide adsorbs. 

 Ethyl alcohol or urethan also inhibit the steady-state luminescence of 

 extracts, at concentrations that are only 2 or 3 times greater than those 

 required for corresponding per cent inhibitions of cellular lumines- 

 cence under similar conditions of temperature and hydrostatic pres- 

 sure. The inhibitory concentrations of alcohol or urethan, however, 

 are considerably higher than those of sulfanilamide, and it is reason- 

 able to suppose that adsorption on inert substances has less effect in 

 altering the concentration initially added to the solution. As in cells, 

 the inhibitory effect of a given concentration of alcohol or urethan on 

 steady-state luminescence increases with rise in temperature and de- 

 creases with rise in pressure. These drugs also affect the spikes: at 

 optimum temperature and normal pressure, the spike is markedly 

 higher in the presence of inhibitory concentrations of either drug. 

 Subinhibitory concentrations of alcohol increase the steady-state in- 

 tensity of luminescence in extracts. Increases in the steady-state inten- 

 sity of cellular luminescence, in the presence of alcohol under certain 

 conditions, have also been noted (cf. Fig. 8). 



The role of the aldehyde remains to be clearly established. In the 

 absence of added aldehyde, the pressure-temperature relationships are 

 different, but the intensity of luminescence is so weak that these rela- 

 tionships have not been determined with a desirable accuracy by 

 means of the methods available in the initial study. The evidence at 

 hand indicates that unless adequate concentrations of aldehyde are 

 present, steady-state levels of luminescence are not significantly low- 

 ered by pressure at low temperatures, and the magnitude of the 

 spikes is somewhat less. Thus, the limiting reactions are not the same 



