CHAPTER IV 



THE CHEMISTRY OF BACTERIA AND THEIR 

 PRODUCTS 



STRUCTURE AND PHYSICAL PROPERTIES^ 



In structure, as in nearl}' all other respects, bacterial cells stand 

 intermediate between the cells of ordinary plant and animal tissues. 

 Their cell wall seems to be generally more highly developed than that 

 of animal cells, and less so than the wall of most plant cells. The much 

 vexed question as to the existence or non-existence of a nucleus seems 

 to be best answered by Zettnow, who considers that the portion of the 

 bacterial cell usually made evident bj^ ordinary staining methods con- 

 sists of a mixture of nuclear substance (chromatin) with non-chromatic 

 substance {end o plasm) ; the outer membrane, which requires special 

 methods for its satisfactory demonstration, consists of a modified 

 cytoplasm {ectoplasm). Some bacteria consist chiefly of chromatin 

 (e. g., vibrios), but the proportion of the different elements varies 

 greatly, not only in different varieties, but also in the same variety 

 under different conditions. The fact that the chromatin is not aggre- 

 gated into the usual nuclear form may be ascribed to the low stage of 

 development reached by bacteria in the scale of evolution; or, as 

 Vejdovosky has suggested, to the extremely rapid rate of cell division 

 in the bacteria which prevents the chromatin from appearing in the 

 resting stage which a nucleus constitutes. Finer structures within 

 the bacterial cell have as yet been only imperfectly discerned. 



The thickness of the ectoplasm varies greatly even in the same 

 species, being generally greatest in older cultures. In some forms 

 the ectoplasm may constitute one-half of the total mass of the cells. 

 The capsule seems to arise through a swelling of the ectoplasm, and 

 is probably present in at least a rudimentary stage in all bacteria 

 (Migula). 



Plasmolysis and Plasmoptysis. — Under conditions of altered 

 osmotic pressure the bacterial cell behaves quite similarlj^ to the plant 

 cell. 2 If placed suddenly in a solution of higher osmotic pressure than 



1 In this chapter references will not generally be given that can be found by 

 consulting Kolle and Wassermann's Handbuch. A general consideration of the 

 Biology of the Bacteria, including references to the effects of light, heat, osmotic 

 pressure, etc., is given by Miiller, Ergb. der Physiol., 190-1 (4), 138; concerning 

 their chemistry see H. Fischer, Lafar's Handbuch der Technischen Mykologie, 

 1908 (1), 222. 



''Literature, see Gotschlich, Kolle and Wassermann's Handbuch, vol. 1. 



101 



