GROWTH FACTORS l09 



The closely related tiiphosphopyridine nucleotide. 

 Co -enzyme II, which is concerned in reduction and 

 phosphorylation reactions, is also required by H. in- 

 fluenzce and H. parainfluenzoi. 



Organisms of the genus Hcemophilus afford another 

 example of symbiosis. H. canis needs hsematin but 

 synthesises Co-enzyme I ; H. parainfluenzce needs co- 

 enzyme I but synthesises haematin. If sown separately 

 in peptone water neither grows. If they are sown 

 together good growi}h results, each organism supplying 

 the other with the lacking factor. 



Pimelic acid— COOH.CH2.CH2.CH2.CH2.CH2.COOH. 

 It was shown by Mueller that pimelic acid was one of the 

 substances in liver extract which was required for the 

 gro^vth of C. diphtherice in sjoithetic media. The syn- 

 thetic acid is equally effective, but other dibasic acids, 

 such as azelaic acid, were not effective. Pimelic acid has 

 an observable effect in concentrations of 0-005 ju-g./ml. 

 and optimum effect at 0-01 [ig./ml. 



Although nothing is kno^vn of the way in which 

 pimelic acid acts it is, perhaps, significant that the 

 acid arises as a result of the hydrolysis and oxidation of 

 biotin (see p. 104). It is possible that pimelic acid may 

 be required in the synthesis of the carbon chain of biotin, 

 the other two carbon atoms of the chain being derived by 

 condensation with acetaldehyde. 



CH2OH 



I 

 C 



Pyridoxine. — CHaOH.t^ * ^j.oh ,2-methyl-3-hydroxy-4:5- 



Hc!« 2C.CH3 



di-(hydroxymethyl) pyridine. This substance has been 

 shown to be a rat anti -dermatitis factor, vitamin Bg, 



