GENERAL SYSTEMATIC BACTERIOLOGY 105 



Key to the Genera of Tribe Streptococceae 



1. Parasites growing poorly, or not at all, on artificial media. 

 Cells usually in pairs Diplococcus 



2. Saprophytes, usually growing in cane sugar solutions. Cells in pairs or chains. 



Leuconostoc 



3. Chiefly parasites. Normally forming short or long chains, sometimes pairs, 



but never packets Streptococcus 



4. Parasites. Cells in groups or short chains, rarely in packets. 



Staphylococcus 



Key to Genera of Tribe Micrococceae 



1. Facultative parasites or saprophytes. Cells in plates or irregular masses 



(never in long chains or in packets) Micrococcus 



2. Cell division occurs in three planes forming packets. 



Sarcina 



3. Saprophytes. Cells in groups or packets. Form red pigment on agar. 



Rhodococcus 



Key to the Genera of Family Spirillaceae 



1. Cells short, bent rods, rigid, single or united into spirals. 



Vibrio 



2. Cells rigid, of various thickness and length and pitch of the spiral, forming 



either long curves or portions of a turn Spirillum 



Key to the Tribes of Family Bacteriaceae 



1. Produce pigment on solid media. The pigment may be red, yellow, violet, 



green or blue Chromobactereae 



2. Without pigment formation on agar or gelatin . Achromobactereae 



3. Cellulose digesting organisms occurring in soil. Cellulomonadeae 



4. Plant pathogens, growth usually whitish Erwineae 



5. Gram-positive rods, growing freely on artificial media. Do not attack 



carbohydrates Zopfeae 



6. Gram-negative rods growing freely on artificial media. Generally act on 



carbohydrates with formation of acid and gas. 



a. Without capsules Bactereae 



7. b. Encapsulated Encapsulateae 



8. Rods often long and slender. Gram-positive. Non-motile. Usually pro- 



duce lactic acid from carbohydrates Lactobacilleae 



9. Anaerobic, non-spore-forming rods Bacteroideae 



10. Gram-negative rods, showing bipolar staining. Parasitic forms. 



Pasteurelleae 



11. Minute parasitic forms growing only (or best) in the presence of hemoglobin, 



ascitic fluid or other body fluids Hemophileae 



Key to the Genera of Tribe Chromobactereae 



1. Small, aerobic rods, producing a red or pink pigment on agar or gelatin. 



Serratia 



