346 Marine Microbiology 



the three-day cultures exposed to hght with an intensity of 1.4 

 X 10^ erg/cm^ sec. is three times less than for cultures exposed to 

 6.28 X lO^ erg/cm^ sec, in this case on the seventh and later 

 on the tenth day, this difference will amount to only 10 to 15 

 per cent. 



In experiments with higher intensities (ranging from 5.77 

 X 10^ erg/cm^ sec. to 13.6 x lO^ erg/cm^ sec.) in which the 

 dynamics of development were observed daily, a great change 

 in the development of cultures was noted in one day; on the 

 second day the cultures exposed to intensities ranging from 9.2 

 and 13.5 X 10^ erg/cm^ sec. exceeded by four to five times the 

 cultures which had received about 5.77 X 10^ erg/cm^ sec; but 

 on the third day and especially on the fourth day the divergence 

 between the cultures considerably diminished (Table 4). 



TABLE 4 



The Dynamics of Development of Chr. vinosum at Exposure 

 Intensities from 5.77 to 13.5x10^ erg/cm^ Sec. 



Table 5 presents data from experiments carried out under 

 the intensity of physiological radiation amounting to 7.35, 11.75 

 and 23.3 X lO^ erg/cm^ sec. The table shows that Chromatium 

 vinosum developed favorably even at exposure intensity of 23.3 

 X 10^ erg/cm^ sec. The bacteria developed successfully also 

 under exposure of 32 X 10^ erg/cm^ sec. On this basis one may 

 assume that the threshold of luminous inhibition of the puiple 

 sulfur bacterium Chr. vinosum is beyond the tested intensities 

 of physiological radiation. 



Therefore, on the basis of the obtained data it is believed that 



