THE PROTEINS OF MICRO-ORGANISMS 337 



pneiimucocci give lihoiuicleic acud to tiie exteJit of 2 to 

 6 per cent, of their dry weight. Staphylococci also give 

 ribonucleic acid but Esch. coli contains desox^a^bonucleic 

 acid. 



It has been shown that the substance responsible for 

 the Gram -positive staining 7-eaction of CI. perfringens is 

 the magnesium salt of ribonucleic acid, which can be 

 removed by extraction with dilute aqueous bile salt 

 solutions leaving a Gram-negative cytoskeleton. The 

 extract itself is also Gram -negative but can recombine 

 with Gram -negative cell residue (but only if the latter is 

 in a reduced condition) to give a Gram -positive complex. 

 The ribonucleate will not combine with normally Gram- 

 negative organisms, nor can desoxyribonucleic acid, 

 nucleotides or nucleosides replace ribonucleic acid. 

 Sacch. cerevisice can be similarly extracted to yield 

 Gram -negative cells and nuclei. The extracted cells of 

 CI. perfringens and Sacch. cerevisice contain basic proteins 

 with a high proportion of arginine and it is suggested 

 that the Gram -positive material is a complex of reduced 

 basic protein and magnesium ribonucleate. Gram- 

 positive organisms often become Gram -negative in old 

 cultures and it has been found that Str. salivarius becomes 

 Gram -negative in media containing little magnesium or 

 in media so acid that magnesium ribonucleate cannot 

 exist. 



It has very recently been shown that the substance 

 responsible for the long known conversion of Rough 

 pneumococci into vSmooth organisms of another type is a 

 desoxyribonucleic acid, characteristic of the type of 

 pneumococcus from which it is derived. Thus an extract 

 from Smooth Tjrpe III cells will cause conversion of any 

 Rough pneumococcus to Smooth Type III but not to 

 any other type ; Smooth Type II extract gives rise to 

 the corresponding Smooth type only. The distinguishing 

 feature of Smooth, compared with Rough, pneumococcus 

 organisms is a non-nitrogenous polysaccharide whose 



