GENERAL SYSTEMATIC BACTERIOLOGY 107 



Key to Genera of Tribe Hemophileae 



1. Aerobic species Hemophilus 



2. Anaerobic species Dialister 



Key to the Genera of Family Bacillaceae 



A. Aerobic forms, mostly saprophites Bacillus 



B. Anaerobic forms. Often parasitic Clostridium 



Key to the Families of the Order Actinomycetales 



A. Filamentous forms, often branched, sometimes forming mycelia. Conidia 



sometimes present. Some species parasitic. .Actinomycetaceae 



B. Parasitic forms. Rod-shaped, rarely filamentous, and with only slight and. 



occasional branching. No conidia Mycobacteriaceae 



Key to the Genera of Family Actinomycetaceae 



A. Parasitic forms. 



a. Aerobic Actinobacillus 



h. Anaerobic or facultative Leptotrichia 



B. A few parasitic forms; mostly soil forms. 



a. Filamentous, often branched, sometimes forming mycelia. 



Actinomyces 



b. Rods forming long filaments which rarelj' show branching. 



Erysipelothrix 



Key to the Genera of Family Mycobacteriaceae 



A. Slender rods; acid fast Mycobacterium 



B. Slender, often slightl}' curved rods; not acid-fast. 



Corynebacterium 



C. Obligate parasites. Cells frequently fusiform. 



Fusiformis 



D. Slender, Gram-negative rods Pfeifferella 



Key to the Families of the Order Chlamydobacteriales 

 One family only: Chlamydobacteriaoeae. 



Key to the Genera of the Family Chlamydobacteriaceae 



1. Filaments usually not permanently attached. 



a. Filaments straight or at least not t-wisted. . Leptothrix 

 h. Filaments twisted Didymohelix 



2. Filaments attached. 



a. Filaments unbranched Crenothrix 



b. Filaments show pseudodichotomous branching. 



1. Swarm cells developed (motile conidia). Usually without a deposit 



of iron in the sheath Sphaerotilus 



2. Spherical, non-motile conidia. Usually with iron oxide. 



Clonothrix 



