:]4G BACTERIOLOGICAL CHEMISTRY 



mannitol and a- and j8-glucoheptitols, as Avas shown by 

 Hibbert and by Khouvine and their co-workers. 



Starch, or a polysaccharide giving a blue colour with 

 iodine, has been recorded as occurring in a number of 

 bacteria and fungi. Colman in 1862 claimed that it was 

 to be found in the spore tubes of Ascomycetes , whilst it 

 is formed by A. niger growing on a synthetic medium. 

 The spores of P. glaucum contain a " spore-starch " 

 which gives a blue colour with iodine and yields glucose 

 on hydrolysis. 



Many bacteria and fungi produce large yields of carbo- 

 hydrate " gums " which may be built up of one or more 

 of several sugar units. Thus Leuconostoc mesenteroides 

 forms dextran, a dextro-rotatory polysaccharide giving 

 glucose on hydrolysis, when grown on glucose and sucrose 

 but not when other sugars, such as melezitose, raffinose, 

 fructose, galactose, lactose, maltose, xylose or glycerol, 

 serve as the source of carbon. The polysaccharide, 

 [ajo + 180° and containing 0-5 per cent, of nitrogen, is 

 also formed by the action on sucrose of a cell-free, sterile 

 extract of the organism. The enzyme has no action on 

 glucose -1 -phosphate, and no inorganic phosphate is 

 liberated during its action on sucrose. Potato phos- 

 phorylase, which converts glucose- 1 -phosphate to starch, 

 has no effect on sucrose ; it is therefore concluded that 

 glucose -1 -phosphate is not an intermediate in the forma- 

 tion of dextran. This dextran has been shown to give 

 serological reactions with antisera prepared against 

 pneumococcus, Types II, XII and XX, but not Types I 

 and III, some Salmonella and Sir. salivarius, as well as 

 the homologous organism. As a result of the proportions 

 of di-, tri- and tetra-methyl methylglucosides formed by 

 hydrolysis of methylated dextran Hil^bert has suggested 

 that the polysaccharide has the branched chain struc- 

 ture : — 



