GENERAL MORPHOLOGY AND PHYSIOLOGY 49 



Cells never in sheathed filaments. Conidia only in the mycelial. 



Mycobacteriaceae. Flagella often present. Free iron, sulphur, or 



bacterio-purpurin never present D. Eubacteriales 



2. ARTIFICIAL KEY TO THE FAMILIES OF THE EUBACTERIALES 



Cells spiral with polar flagella IV. Spirillace 



Not as above 



Cells spherical; rarely, if ever, motile; spores never produced; never 

 securing growth energy from nitrogen or ammonia . . V. Coccaceae 

 Not as above 



Cells short rod-shaped with a single rarely two polar flagellum; usually 

 forming green or yellow pigment .... III. Pseudomonadaceae 

 Not wholly as above 



Spores formed VIII. Bacillaceae 



Spores never formed 



Metabolism simple, securing growth energy form carbon, hydrogen 

 or their simple compounds ; flagella, if present, 



polar I. Nitrobacteriaceae 



Metabolism complex, dependent upon more complex carbohydrate 

 and protein substances; flagella, if present, peritrichic. Cells 

 clubbed, fusiform, filamentous, branching or mycelial; those not 

 distinctly so are either acid-fast or show barred irregular 



staining II. Mycobacteriaceae 



Not as above 



Gram-positive; non-motile VII. Lactobacillaceae 



Gram-negative; often motile VI. Bacteriaceae 



3. ARTIFICIAL KEY TO THE GENERA OF THE EUBACTERIALES 



I. Nitrobacteriaceae 



Fixing nitrogen or oxidizing its compounds 

 Fixing nitrogen 



Cells large; in soil 7. Azotobacter 



Rods minute; in roots of leguminous plants .... 8. Rhizobium 

 Oxidizing nitrogen compounds 



Oxidizing ammonia 5. Nitrosomonas 



Oxidizing nitrites . . . 6. Nitrobacter 



Not as above 



Oxidizing carbon compounds 



Oxidizing alcohol; branching forms common ... 4. Mycoderma 

 Not as above, using simpler carbon compounds 



Oxidizing CO 3. Carboxydomonas 



Oxidizing CH4 2. Methanomonas 



4 



