PRODUCTS OF THE LOWER FUNGI 305 



to be a product of P. hrevirtntlc when (^ixjwu on bread 

 containing inorganic arsenic compounds. Dimethyl 

 selenium and dimethyl tellurium were similarly formed 

 from sodium seleiiide and potassium tellurite respectively 

 by P. brevicaule, P. chrysogenum and P. notatum. Di- 

 methyl ethyl arsine, (CH3)2.C2H5.As, arises from sodiimi 

 ethyl arsonate and methyl diethyl arsine, CH3.(C2H5)2.As, 

 from diethyl arsenic acid ; n-propyl arsonic acid gives 

 rise to dimethyl n-propyl arsine, (CH3)2.C3H7.As, in the 

 same way. Similar derivatives of antimony could not be 

 obtained by the growth of P. brevicaule in potassium 

 antimony tartrate nor does the mould methylate sulphur. 

 Challenger has suggested that the methylation is through 

 the agency of choline or betaine which contains a mobile 

 methyl group capable of being transferred under biological 

 conditions, as shown by experiments using choline or 

 betaine containing methyl groups " marked " with heavy 

 hydrogen. 



The wood rotting fungus, Schizophyllmn commune, 

 when grown on a synthetic medium containing inorganic 

 sulphates produces methyl mercaptan, CH3.SH. 



A. sydowi, which can also produce volatile arsenic 

 compounds, is capable of incorporating the inorganic 

 sulphur of the medium into cyclic choline sulphate, 



I I , which IS an anhydride of choline 



sulphate. It has been shown that Verticillium albo-atnun 

 and Botrytis cinereci, when grown on a medium containing 

 asparagine and ammonium salts as sources of nitrogen, 

 produce thiourea. The production of biotin (see p. 103) 

 and of penicillin (see p. 171) obviously also involves the 

 metabolism of inorganic sulphate with, formation of 

 organic sulphur compounds, as does, of course, the 

 synthesis of proteins which all contain sulphur in some of 

 their amino acids and as SH groups, and which are formed 

 by all micro-organisms. 



