VISCOSITY AND REACTION RATES IN BACTERIA 



363 



0.00 



•0.02 



-0.04 



Chromatium 



Glycerol (67%) 



410 



420 



X(m/A) 



430 



Fig. 4. The effect of glycerol upon the difference spectrum 

 for cytochrome oxidation in Chromatium . {MN -16). 



presence of glycerol than in its absence. Lastly, a consistent inhibition 

 of the rate of the light-off reaction is observed. 



An examination of the difference spectrum for the light effect in 

 the presence of glycerol shows the peak to be somewhat intensified and 

 shifted toward shorter wavelengths (Fig, 4). The maximum is approxi- 

 mately 422 m^, the wavelength employed in Fig. 3. 



Rho do spirillum rubnim. 



A series of experiments illustrated in Fig. 5 indicate the effect of 

 the aerobic- anaerobic transitions in R. rubrum (A), followed by illumi- 

 nation of the cells. The illumination interval is plotted on an enlarged 

 scale in B; it is seen that the light reaction can readily be measured 

 from the slopes of the traces. The effect of 40 per cent glycerol is 

 indicated in Record C. First, it is seen that the respiratory activity 

 is much slower, as evidenced by the prolonged interval required to 

 reach the anaerobic steady state. Illumination gives approximately the 

 same percentage change of steady states. In the enlarged view (D), one 

 sees that the light-on reaction proceeds very rapidly in spite of the 

 presence of 40 per cent glycerol but that the light-off reaction is con- 

 siderably slowed. Thus, we see characteristics in R. rubrum similar 

 to those in Chromatium and, on this basis, our data are consistent 

 with the possibility that the cytochrome-bacteriochlorophyll electron 

 transfer reaction in R. rubrum is of a similar mechanism to that of 

 Chromatium. 



