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- 



» I 



FlG. 19. — Saecina. 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 Bacteeiaceae 



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 



jijQ 21 er. not have polar flagella only. In most genera 



tthbobacillos the cells are gram-negative. Fluorescent 

 pigment is not produced. The important genera are 

 Erythrobacilliis, Erwinia, Proteus, Bacterium, Pasteurella, 

 Hemophilus, and Lactobacillus. 



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. 



