CLASSIFICATION OF THE BACTERIA 37 



IV. FAMILY PSEUDOMONADACEAE 



This family contains a single genus, Pseudomonas. The 

 cells are rod-shaped, and usually motile by means of polar 

 flagella. Frequently a fluorescent green or brown pigment 

 is produced in culture media. In other species an insolu- 



tt 

 * I 



FIG. 19. SARCINA. FIG. 20. PSEUDOMONAS. 



ble yellow pigment is formed. Among those producing a 

 green fluorescent pigment is the Pseudomonas aeruginosa, 

 an organism sometimes found in wounds. Many of the yel- 

 low and a few white species produce diseases in plants. 



V. FAMILY BACTERIACEAE 



This is the largest of the families of bac- 

 teria. It includes those rod-shaped bacteria 

 whose cells are usually regular in shape, do 

 not produce endospores, and when motile do 



FlG 21 E B . n t nave polar flagella only. In most genera 



YTHBOBACLLLUS the cells are gram-negative. Fluorescent 

 pigment is not produced. The important genera are 

 Erythrobacillus, Erwinia, Proteus, Bacterium, Pasteurella, 

 Hemophilus, and Lactobacilhts. 



Erythrobacillus. The organisms of this group are small 

 aerobic bacteria, producing a red or pink coloring matter, 

 sometimes yellow or orange. Some species are motile. 

 The most important species is Erythrobacillus prodigiosus. 



