114 BACTERIOLOGICAL CHEMISTRY 



with some difficulty, to grow in the absence of the extract, 

 or, in other words, to produce its own growth factor. 

 The substance, which is acidic in nature, is very stable 

 and can be extracted by glycerol, hot water, hot alcohol 

 or hot acetone. It can be replaced by alcoholic extracts 

 of a number of vegetable tissues and fungi. It can be 

 partially replaced by 0-1 /xg./ml. of phthiocol, 3-hydroxy- 

 2 -methyl- 1 : 4 -naphthoquinone, a constituent of tubercle 

 bacilli (see p. 392), or of 2 -methyl- 1 : 4 -naphthoquinone, 

 the anti-haemorrhagic vitamin K. 



The Sporogenes Factor. — CI. sporogenes, when inocu- 

 lated as a spore suspension into synthetic media shows 

 no growth. When active preparations from yeast or 

 from urine are added in very small quantities (0-4 /xg./ml.) 

 good growth ensues. The factor is widely distributed in 

 animal and vegetable tissues from which it can be ex- 

 tracted by 75 per cent, alcohol. It can be purified by 

 conversion into an alcohol soluble barium salt. The 

 regenerated acid is active in concentrations of 0-02 

 /Ag./ml. It can be further purified by distillation of its 

 methyl ester in a high vacuum (boiling point, 80 to 

 100°C. at 0-001 mm. of mercury). The ester is inactive 

 but the activity is restored on hydrolysis. The sporogenes 

 factor is an unsaturated hydroxy fatty acid, C11H14O4 or 

 C11H12O4, of molecular weight about 200. Its presence 

 appears to be essential for the growth of CI. botulinum 

 and CI. welchii as well as of CI. sporogenes. It is produced 

 by many, probably all, aerobic bacteria, for example. 

 Salmonella typhhnurium, Eherthella typhosa, and M. 

 tuberculosis and by the mould Aspergillus versicolor. It 

 is probable that it is required by all micro-organisms 

 but that the Clostridia have lost the power of sjnithesising 

 it for themselves. 



It will have been noticed that many of the substances 

 listed as growth factors are the prosthetic groups or the 



