Some Biochemical Differences 439 



DISCUSSION 



Knowledge of the general biochemistry of Desidfovibrio 

 desulfiiricans is still rather fragmentary, but the published data 

 reviewed recently (15) show no indication of essential differences 

 in the contents of pigments and metabolic enzymes between salt 

 water and fresh water strains. Hence such differences as must 

 exist are likely to be of more subtle kinds. The present study 

 has demonstrated tluee physiological differences that seem to 

 be consistently maintained and we can put forward four tentative 

 conclusions concerning growth of the strains studied in a saline 

 environment: 



(i) Growth in a saline environment increased the osmotic 

 stabilit>^ of O.F.V.s prepared from the organisms. 



(ii) Growth in a saline environment was associated with 

 production of a mucopolymannoside which was not chemically 

 related to the cell wall. 



(iii) Growth in a saline environment led to an increased 

 content "free amino-acid material" within the cell and to a 

 change in its quality. 



(iv) Adaptation of a fresh water strain to a saline environ- 

 ment included the acquirement of the three characters listed 

 above, together with a morphological change. For an adaptive 

 change in the reverse direction only the last character was studied 

 and it was not lost. 



It is reasonable to suppose that the possession of the ap- 

 propriate characters has survival value for the organisms in a 

 given environment, but the connection between some of the char- 

 acters reported here and survival in the marine environment is 

 not immediately clear. The data presented here may be a useful 

 pointer to further work, l^ut studies of more strains as well as 

 investigation of other cliaracters are necessary before a useful 

 comprehensive rationalization of these findings could be at- 

 tempted. 



ACKNOWLEDGMENTS 



We are indebted to Mrs. S. C. Hale (nee Selwyn) for con- 

 siderable assistance with the studies on osmotically fragile bodies. 

 This contribution is published by permission of the Director, 

 National Chemical Laboratory. 



