BIOGRAPHICAL MEMORANDA 



teria photosynthesis, and a year later Roelofsen [1934, 1935TI1], in 

 the same institute, made the important discovery that molecular hy- 

 drogen can also fulfil this function. Kluyver's continued interest in 

 this subject has made itself felt in the many and important contribu- 

 tions to photosynthesis published by the 'Biophysical Group' in Utrecht, 

 largely supported by the Rockefeller Foundation, and of which Kluy- 

 ver was one of the two directors. 



This same group also significantly advanced our knowledge of 

 bioluminescence. Although several of the publications on this phe- 

 nomenon deal with its physical aspects, some were clearly inspired 

 by the comparative biochemical approach; these may here be men- 

 tioned in particular. 



In a series of measurements on the relation between oxygen con- 

 sumption and intensity of luminescence of suspensions of luminous 

 bacteria under diverse conditions, it was convincingly established that 

 specific inhibitors of respiratory activity could reduce the rate of 

 oxygen utilization by a large factor without appreciably diminishing 

 the amount of radiant energy emitted. This result led to the notion 

 that bioluminescence, although characteristically an oxidative pro- 

 cess, should be interpreted as an incidental side reaction of the normal 

 respiratory mechanism. It also became the basis of a simple modifi- 

 cation of Beijerinck's classical method for demonstrating the depend- 

 ence of bioluminescence on the presence of oxygen, with which this 

 point can be illustrated in a striking and elegant manner. The exper- 

 iment of Beijerinck is carried out as follows: a glass tube is filled al- 

 most completely with a suspension of luminous bacteria, whereupon 

 the open end of the tube is closed off. After standing for some time the 

 suspension no longer emits light except at the very boundary between 

 the liquid column and the gas phase, because the oxygen initially 

 present in the suspension has been completely consumed. If now 

 one turns the tube upside-down, the air passes through the liquid, 

 which causes the entire suspension temporarily to become luminescent 

 once more ; the duration of this spectacle depends on the amount of 

 oxygen that has gone into solution as the air bubble passes through the 

 suspension, and on the rate of its consumption, which latter is nor- 

 mally determined by the density of the suspension. The experiment 

 can be repeated many times, and will only fail if all the oxygen in 

 the gas phase has been used up. 



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