COMPARATIVE STUDIES ON RESPIRATION. 



X. Toxic and Antagonistic Effects of Magnesium in Relation 

 TO THE Respiration of Bacillus subtilis. 



By matilda MOLDENHAUER BROOKS. 



{From the Laboratory of Plant Physiology, Harvard University, Cambridge, 

 and the Marine Biological Laboratory, Woods Hole.) 



(Received for publication, January 14, 1920.) 



The behavior of magnesium is of special interest since in studies on 

 antagonism magnesium has been found to occupy an intermediate 

 position between the monovalent and the bivalent metals. In many- 

 cases it can act as an antagonist to calcium as well as to sodium. As 

 no investigations on respiration have been undertaken from this 

 point of view, the writer has made some experiments on this 

 subject. 



The experiments of Lipman^ on the rate of ammonification of Bacil- 

 lus subtilis have shown that there is some antagonism between sodium 

 and magnesium. On the other hand he found no antagonism, but 

 increased toxicity, when magnesium and calcium were combined.^ 

 Kelley,^ in studying the ammonification and nitrification of certain 

 soils, found no antagonism between magnesium and sodium. This 

 sort of antagonism was observed, however, in the case of nitrogen 

 fixation by Azotohacter chroococcum, as reported by Lipman and 

 Burgess.^ 



In view of these facts it seemed desirable to study the effects of 

 magnesium upon the respiration of Bacillus subtilis. The technique 

 employed was the same as that described in a previous publication.^ 



1 Lipman, C. B., Bot. Gaz., 1910, xlix, 207. 



2 Lipman, C. B., Bot. Gaz., 1909, xlviii, 105. 



^Kelley, W. P., Univ. of Calif ornia Pub., Agric. Sc, 1912, i, 39. 

 * Lipman, C. B., and Burgess, P. S., /. Agric. Sc, 1914, vi, 484. 

 5 Brooks, M. M., /. Gen. Physiol, 1919-20, ii, 5. 



331 



