CHAPTER IV 



THE CHEMISTRY OF BACTERIA AND THEIR 

 PRODUCTS 



STRUCTURE AND PHYSICAL PROPERTIES ' 



In structure, as in uearly all other respects, bacterial cells stand 

 inteiinediate between the cells of ordinary plant and animal tissues. 

 Their cell wall seems to be generally more hig-hl}- developed than that 

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

 composition, however, the wall is more closely related to animal than 

 to vegetable tissues. 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 by ordinary staining methods consists of a mixture of nuclear 

 substance {chroiiiati)i) with non-chromatic substance {endoplasm) ; 

 the outer membrane, which requires special methods for its satisfac- 

 tory demonstration, consists of a modified cytoplasm {ectoplasm). 

 Some bacteria consist chiefly of chromatin (e. g., vibrios), but the 

 proportion of the ditit'erent elements varies greatly, not onh^ in dif- 

 ferent varieties, but also in the same variety under ditferent con- 

 ditions. The fact that the chromatin is not aggregated 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 pre- 

 vents the chromatin from appearing in the resting stage whicli a 

 nucleus constitutes. Finer structures witliiu tlie bacterial cell have 

 as 3'et been onl}^ 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 rudiniontary stage in all bacteria 



LMiguhi).' 



F^lasmolysis and Plasmoptysis. — I'mler conditions of altered 

 osmotic pressure the bacterial cell behaves quite similarly to the plant 



1 In this chapter reforcnees will not ponorally he <iiven that can he found hy 

 consul(in<j: Kolio and \Vass(>iinann's TIandliucli. A jxcncral consideration of the 

 Bio]o<,'y of the Bacteria, incliidinjj refercn<es 1o llie ctVecls of lijilit, heat, osmotic 

 pressure, etc., is friven hv Miiller, Krgb. der Physiol., 1004 (4), 13S; concerninc 

 their chemistry see H. Fisciier, Lafar's IIandl)uch der Teclinischcn ^lykologie, 

 1908 (1), 222." 



lOfl 



