INHIBITORS AND PHOTO PIGMENT SYNTHESIS 



57 



120 



180 240 



MINUTES 



300 



360 



Fig. 3. Effect of amj^al on growth and bacteriochlorophyll synthesis. The ex- 

 periment was conducted as described in the legend of Fig. 1, except that at 

 zero time one culture (open points) received amytal (1.6 x 10-3 jv/). Symbols 

 as for Fig. 1. 



These results can be summarized by saying that amytal mimics the 

 effect of a sudden ^gcrease in light intensity, while DNP and dicoumarol 

 mimic the effect of a sudden increase in light intensity. Bacterio- 

 chlorophyll synthesis is completely, although temporarily, inhibited by 

 the latter compounds. When the growth rate is reduced by lowering the 

 temperature or by addition of 5-methyl-tryptophan there is only a 

 partial inhibition of bacteriochlorophyll formation, 



Dicoumarol and DNP presumably uncouple phosphorylation and 

 electron transport; consequently, the electron transport chain becomes 

 more oxidized and bacteriochlorophyll synthesis is stopped. However, 

 the specific pigment content will decrease because of continued growth 



