ANHYDRIOBIOSIS 23 



Lion then investigated the protective properties of Naylor's 

 medium. Using each of its components separately and in com- 

 bination, he found that only the thiourea protected bacteria 

 from the lethal effects of oxygen (Fig. 5). 



Of various analogs of thiourea tested, such as methyl thiourea, 

 dimethyl thiourea, trimethyl thiourea, thioacetamide, urethan, 

 etc., only those in which the amino group was not totally 

 substituted, and which had the S=C rather than the 0=C 

 link, had protective powers. 



In view of reports on the protective properties of glucose, 

 many sugars, monosaccharides, disaccharides, and trisaccharides 

 were tested. In addition, the protective effects of inorganic salts 

 with different cations and anions were tested, as well as those of 

 reducing agents such as glutathione, cystein, cysteamine, sodium 

 hydrosulfite, etc. 



Table I summarizes the results. It may be seen that of the 

 inorganic salts, the Na cation, iodides, thiocyanates and nitrites 

 are particularly effective in protecting bacteria against the lethal 

 effect of air. The protective effect of Nal exceeds even that of 

 thiourea. 



As to the sugars, their protective properties depended neither 

 on their being fermented by the bacteria (lactose is fermented like 

 glucose, but lacks protective properties), nor on their reducing 

 character (m.altose which is reducing but not fermented lacks 

 activity, while a-methyl glucoside which is not reducing and not 

 fermented protects very well). 



Cystein and glutathione even increased the lethal effect of 

 oxygen while colloids like albumin or dextran had no effect 

 whatsoever. 



In another set of experiments it was found that the protective 

 substances may be added as late as ten seconds before freezing, 

 and still prevent death due to oxygen, thus indicating that they 

 have no metabolic effect. They were, however, ineffective when 

 added to the dried bacteria in the resuspending medium after 

 exposure of the organisms to air. 



Another very important finding was that the degree of 



References p . 29 



