984 



7. MERCURIALS 



occurs with the arsenicals, since Benigno and Santi (1946) found that 

 staphylococci tolerant to Hg++ grow when they have taken up much more 

 Hg++ than is required to prevent growth of the normal strain. The situation 

 with respect to the thiol content of the resistant organisms is confused, 

 since Akiba and Ishii (1952) showed that E. coli tolerant to PM have less 

 SH groups than normally, and Gerardin and Kayser (1959) found that tol- 

 erant Candida utilis contained 6 times more SH groups than the normal 

 strain. Zambonelli (1958 a,b) has obtained evidence that adapted yeast 

 produces more HgS and believed that this inactivates much of the Hg++. 

 Normal yeast produces HgS only from sulfite, whereas adapted strains pro- 

 duce it from sulfate and hyposulfite in addition, although not from cysteine 

 or glutathione. If the resistant strains are grown with only cysteine or glu- 

 tathione as the source of sulfur, Hg++ readily inhibits their growth. If 

 metabolic changes occur during adaptation, they are not marked. Thus 

 resistant Candida respires normally (Gerardin and Kayser, 1959) and re- 

 sistant yeast ferments glucose at the normal rate, although the respiration 

 may be slightly higher (Imshenetsky and Perova, 1957). Claus (1956) has 

 shown that the respiration of Aerobacter aerogenes is initially depressed by 

 Hg++ but recovers after several hours and reaches normal levels (Fig. 7-46). 



Fig. 7-46. Effects of Hg++ on the respiration of Aerobacter 

 aerogenes. The O2 uptake is given as mm^ Oj/ml/SO min. A: 

 Initial exposure to Hg++; B: inoculation of organisms from 

 3 in A and re-exposure. C, control; 1, 0.0011 mM; 

 2, 0.0022 mM; 3, 0.0044 mM; 4, 0.0088 mM; 5, 0.0178 

 mM; 6, 0.037 mM. (From Claus, 1956.) 



Adaptation to mercurials is apparently specific in most cases, since Se- 

 verens and Tanner (1945) found that Salmonella sp. tolerant to Hg++ are 

 not tolerant to Cu++, and vice versa, while Launoy and Levaditi (1913) 

 showed that spirochetes tolerant to antisyphilitic mercurials are not 

 tolerant to arsenicals. However, Blumenthal and Pan (1963) noted that 

 penicillin-resistant strains of staphylococci are more apt to be resistant to 



