CLASSIFICATION OF THE BACTERIA 29 



OUTLINE OF BACTERIAL CLASSIFICATION 



It was noted above that two only of the five orders of 

 bacteria will be discussed : the order of the true bacteria or 

 Eubacter idles, and the order of the thread bacteria or Acti- 

 nomycetales. 



ORDER EUBACTERIALES 



This order contains the forms usually termed the true 

 bacteria, that is, those which are considered least differen- 

 tiated and least specialized. They do not require hydrogen 

 sulphide or other sulphur compounds in abundance, and 

 the cells do not contain either sulphur granules or bacterio- 

 purpurin. The cells may be motile by means of flagella or 

 nonmotile, but they are never notably flexuous. Cell multi- 

 plication is always by transverse fission. Some of the gen- 

 era, particularly among the rod-shaped types, produce endo- 

 spores. The cells are usually minute and spherical, rod- 

 shaped, or spiral in shape, not commonly producing true 

 filaments, and never branching except in the so-called invo- 

 lution forms. This order includes most of the common bac- 

 teria. Altogether seven families belonging to order Eubac- 

 teriales are recognized. The following key may be used for 

 the differentiation of the families : 



KEY TO FAMILIES OF THE EUBACTERIALES 



A. Securing growth energy by direct oxida- 

 tion of carbon, hydrogen or nitrogen or 

 their compounds. Aerobic. Cells rod- 

 shaped or occasionally spherical I. Nitrobacteriaceae. 



AA. Not securing growth energy solely as 

 in preceding. 



B. Cells producing endospores II. Bacillaceae. 



BB. Cells not producing endospores. 



C. Cells spherical 



CC. Cells not spherical. ^ III. Coccaceae. 



D. Cells rod-shaped. 



