62 BACTERIOLOGICAL CHEMISTRY 



ascribed various structures. The glycogen of yeast is 

 the most well known and satisfactorily proved of these ; 

 it is also said to occur in many bacteria. There is still 

 controversy as to whether the " granulose " of such 

 anaerobic bacteria as Clostridium hutyricum (Granulo- 

 hacter butylicum) is true starch or not, in spite of giving 

 a blue colour with iodine and being hydrolysed by 

 amylase. The amount of these polysaccharides (starch, 

 glycogen, granulose, iogen, etc.) varies with the age of 

 the cell and the amount of nutrient material available ; 

 their quantity falls off if the organism is starved and 

 immediately rises again if the cells are transferred to a 

 rich medium. 



Simpler carbohydrates also occur in micro-organisms. 

 Thus trehalose, a non-reducing disaccharide composed of 

 two glucose units, is to be found in yeast and many 

 moulds, up to 4-5 per cent, of Aspergillus niger consisting 

 of this substance. Pentoses occur in the nucleoproteins 

 of micro-organisms. 



The hexahydric alcohol, maimitol, is common in 

 moulds, especially in species of Aspergillus and Peni- 

 cillium, and in some bacteria. 



Lipoids. — The lipoids comprise all those compounds 

 which are soluble in the so-called " fat solvents," ether, 

 alcohol, acetone, chloroform and light petroleum. The 

 fats, waxes and phosphatides and certain of their break- 

 down products, such as the fatty acids, are thus included 

 in this group. As mentioned earlier the fat droplets in 

 micro-organisms can be stained in various ways, black 

 by osmic acid, red by Sudan III, blue by a- or ^-naphthol 

 and dimethyl-p-phenylenediamine in weak alkaline solu- 

 tion, or yellow by dimethyl amido-azobenzene. 



The total lipoid content is usually regarded as corre- 

 sponding to the material extracted by ether, which may 

 vary from 1-6 per cent, of the dry weight of Coryne- 

 bacterium diphtherice to 41 per cent, of Mycobacterium 

 tuberculosis. In yeasts the content varies from 2 to 5 



