8 HAROLD R. CURRAN 



Other future studies should include a reexamination of the mineral re- 

 quirements for sporulation of cells of the genus Clostridium using basal 

 media rendered as metal-free as possible. Synthetic media are usually more 

 complicated for species of Clostridium than for species of Bacillus and there- 

 fore might be considered more difficult to demineralize. However, it may 

 be recalled that Drs. Shankar and Bard at Indiana University in 1952 grew 

 cells of C. perfringens in demetalled media plus known concentrations of 

 certain essential ions. A sequel to their study might consist of the testing 

 of various combinations of metallic ions with this basal medium to learn 

 if sporulation. in addition to vegetative growth, could be obtained. 



A different type of unsolved problem in this general area of sporulation 

 research concerns the possible occurrence of metals that are required for 

 vegetative growth but not for spore formation. The solution of this problem 

 would be facilitated, of course, by the development of techniques for de- 

 mineralizing washed vegetative cells without impairing their viability for 

 should I say without injuring their ability to sporulateK 



Other problems in sporulation research that would be aided by a com- 

 plete knowledge of the mineral requirements for spore formation include 

 those associated with the age and previous history of the cells. For exam- 

 ple: during which phase of vegetative growth are the various essential 

 metals required? 



I believe that as the conference progresses, additional problems associ- 

 ated with mineral requirements may occur to us — and, perhaps some an- 

 swers to the problems Dr. Curran and I have outlined will also be forth- 

 coming. 



Informal Discussion 



CuRRAN: I would like to comment on Dr. Weinberg's mention of an as- 

 say procedure for manganese. According to my information, the chemists 

 lack a delicate test for detecting manganese in the presence of considerable 

 amounts of iron. I think about 0.1% is the least they can detect. In con- 

 nection with our studies on the need of manganese for sporulation. we find, 

 by plotting the logarithms of spores against the concentration of manga- 

 nese, that the sporulation curve rises abruptly around .01 to 03 /ig of man- 

 ganese, so this may provide us with a relatively delicate test for manganese 

 in the presence of large quantities of iron. 



Orin Halvorson: Did the spores produced in low concentrations of man- 

 ganese show any differences other than the difference in heat resistance? 



Curran : This again is Grelet's work. He found that in the absence of 

 manganese the spores were smaller when he started below certain levels of 

 manganese and their refractivity was lower. In one of his tests using an 



