BIOTIN 



rabbit uterus or on rabbit intestine when these were suspended in 

 solutions containing up to i part in 40,000 of biotin or when a frog's 

 heart was perfused in situ with a solution containing 200 /xg. of biotin. 

 Feeding excess biotin caused fatty livers, which contained large 

 amounts of cholesterol. The effect was inhibited by ^g^ white, 

 lipocaic or inositol when these were given at the same time as the 

 biotin 2 (see page 572). 



References to Section 14 



1. J. L. Schmidt and M. Landy, Proc. Soc. Exp. Biol. Med., 1942, 49, 



82. 



2. G. Gavin and E. W. McHenry, /. Biol. Chem., 1941, 141, 619. 



15. BIOTIN IN THE NUTRITION OF 2VUCRO-ORGANISMS 



Yeasts 



Biotin is an important growth factor for a number of micro- 

 organisms and can be detected by the yeast growth method (page 

 421) in as low a concentration as i part in 10,000,000,000.^ It is 

 essential for the growth of many strains of Saccharomyces cerevisiae ^ 

 and for the vast majority of a large number of other yeasts tested.^ 

 Many yeasts can utilise instead of biotin, desthiobiotin (page 447) 

 which is transformed into biotin within the cells.* Bacteria, however, 

 cannot utilise desthiobiotin in this way. Biotin was the only member 

 of the vitamin B complex that definitely increased the production of 

 alcohol by yeast. ^ 



The biotin content of different yeasts varies considerably, the 

 lowest value found in a series tested being 0-23 /xg. per g. and the 

 highest 7-6 jxg. per g.^" Some yeasts, e.g. S. cerevisiae, took up large 

 amounts of biotin from the culture medium, whereas others, e.g. 

 Endomyces magnusii, took up hardly any, although both require 

 biotin for growth ; obviously the uptake is not correlated with the 

 requirement in different species. Torulopsis utilis and Hansenula 

 anomala, which synthesise biotin, also did not take up biotin from the 

 medium. 



Other Fungi 



Biotin was necessary for the growth of a number of moulds includ- 

 ing Lophiodermum pinastri and Ashhya (Nematospora) gossypii,^ 

 Trichophyton alburn,"^ Eremothecium ashhyii,^ Neurospora sitophila and 

 its " pyridoxineless " X-ray mutant,^ Hypholoma fascicular e ' and 

 Marasmius androsaceus.^^ Biotin also stimulated the growth of 



438 



