EFFECT OF CARBON DIOXIDE ON BACTERIA 



"5 



left open. It may be presumed that the 

 C0 2 liberated during respiration diluted 

 the oxygen. 



Chapin (1918), following Wherry's 

 technique in primary isolation of the 

 gonococcus, carried the method a point 

 further, and applied carbon dioxide gas 

 directly. He obtained good growth over 

 a wide variety of concentrations. The 

 author also suggested that the growth of 

 B. subtilis not only diminishes oxygen, 

 but supplies carbon dioxide as well. 

 Hence, the same object could be attained 

 by supplying C0 2 or by placing a lighted 

 candle in the jar with the plates. 



Cohen's work was severely criticized by 

 Gates (1919). The latter claimed that 

 ascribing microaerophilic properties to 

 the meningococcus was an error, since the 

 organisms would grow successfully in 

 atmospheres of Z4, 3Z and 40 per cent 

 oxygen. Reduction of oxygen to 15 and 

 18 per cent respectively showed no inhibi- 

 tive or benefitting influence over the 

 control plates kept under ordinary atmos- 

 pheric conditions. Growths were equally 

 good at any points within 10 and 30 per 

 cent carbon dioxide, as long as the reac- 

 tion of the medium remained favorable. 

 The author concluded that if there was 

 any effect from carbon dioxide it was due 

 to changing the reaction of the medium 

 and making it favorable for the meningo- 

 coccus. 



St. John (1919) denied that there is any 

 influence exerted by C0 2 on the meningo- 

 coccus, and attributed the beneficial results 

 entirely to the increased moisture content 

 in the closed system. Kohman C I 9 I 9) 

 supported the view that carbon dioxide 

 is beneficial to the meningococcus, by 

 delicately adjusting the reaction to the 

 optimum pH range of the meningococcus. 

 By this adjustment a buffer system was 

 created and further deviations of pH pre- 

 vented. 



Stokes (1910), and Gershenfeld (192.0) 

 published their results of examinations of 

 carbonated beverages, undertaken largely 

 from the public health standpoint. It 

 appears, according to them, that a very 

 large per cent of carbonated beverages on 

 the market showed high bacterial counts. 

 The possibility of intestinal infection 

 through the consumption of such bever- 

 ages is pointed out. 



The interest in primary cultivation of 

 the gonococcus and other organisms of this 

 type under increased carbon dioxide ten- 

 tion, or sometimes reduced oxygen ten- 

 sion, has not in the least abated. Herrold 

 (192.0) described a modification of the 

 partial tension method whereby good 

 results were obtained. This consisted in 

 inverting the plates inoculated with 

 gonorrheal material over a plate inocu- 

 lated with B. subtilis, and joining the 

 two plates with a rubber band. Bicarbon- 

 ate was used also, instead of B. subtilis 

 in the lower plate. By the addition of 

 1 per cent sulphuric acid carbon dioxide 

 was liberated and the conditions necessary 

 for growth furnished. 



Swartz and Davis (192.0) created partial 

 tension conditions by heating the tubes 

 and sealing them with rubber stoppers. 

 Upon cooling, reduced tension was 

 obtained. This facilitated the handling 

 of a large number of cultures. 



Huddles on (19^0) changed from the 

 B. subtilis tandem culture method for 

 culturing Bact. abortus to one in which an 

 atmosphere containing 10 per cent carbon 

 dioxide by volume was employed. The 

 same object, i.e., increased C0 2 content, 

 was attained by him when the culture 

 tubes were sealed. His observations are 

 in accord with those of Cohen and Fleming 

 (1918), and of Ruediger (1919), with the 

 meningococcus, and of Chapin (191 8) with 

 the gonococcus. He apparently recog- 

 nized the importance of carbon dioxide 



QUAE. BBV. BIOL., VOL. Ill, NO. 2 



