Effect of Sulfur-Containing Compounds on Growth and Hydrogen Sulfide Production by Bacterium tularense . ∗

Abstract

Summary and Conclusions

1. Of all the substances studied, cystine, cysteine, and to a much lesser extent thioglycollic acid were the only compounds effective in promoting growth of Bad. lularense. 2. Under the conditions described it is confirmed that cystine or cysteine is an essential component of media for cultivation of Bad. tularense, as was found previously. 1 , 4 The effectiveness of glutathione could be ascribed to the cysteine moiety of the tripeptide, while that of thioglycollic acid may not be due to the utilization of the acid per se but to some intermediary metabolic product common to cystine and cysteine. 3. Inasmuch as practically no stimulation of growth of Bad. tularense by methionine and homocystine was observed, it appears justifiable to conclude that cystine and cysteine were not elaborated from these compounds. It is of interest to note that this is in contrast to results reported with animals. 12-18

4. Whenever definite growth of Bad. tularense was observed hydrogen sulfide was formed. It is not possible at present to state the paths of the reactions leading to hydrogen sulfide production from cystine and cysteine by this organism. It may be that the same mechanism prevails as was postulated by Fromageot 19 and Desnuelle 20 for other bacteria and Smythe 21 for liver tissue. 5. Ben-zylation of the -SH radical of cysteine and glutathione or benzoylation of the alpha amino groups of cysteine or cystine prevents the utilization of these amino acids for purposes both of growth and hydrogen sulfide production by Bact. tularense. These results parallel those obtained in metabolic experiments with animals. 22 Apparently this bacterium lacks the mechanism for effective splitting of benzyl and benzoyl radicals from the substituted amino acids. 6. Since homo-cystine did not permit growth or production of hydrogen sulfide by Bact. tularense while cystine was highly effective in both these respects, it is apparent that the length of the carbon chain as well as the availability of amino and -SH or S-S groups is of importance in the reactions involved.