30. Organisms grow on agar under aerobic conditions only if heavy inocula are used; slightly pleomorphic, including branched forms; 'propionic acid is produced fro7n glucose and also from lactic acid; catalase-positive. . . Propionibacterium p. 569 (P. arabinosum) Not as above 31 31. Small spindle-shaped cells usuallj^ occurring in long intertwined chains in liquid media; microaerophilic; ferments glucose with the production of ethyl alcohol with small amounts of CO2 and acetic acid and possibly lactic and formic acids; acid and gas in glucose in 3 to 5 days Zymobacterium p. 577 Not as above 32 32. Colonies usually 1 mm or less in diameter, colorless, little or no growth on media de- void of carbohydrates; rods frequently arranged in chains, grow in glucose broth, producing a pH much below 6.0; acid produced from lactose by all species except L. delbrueckii and L. brevis Lactobacillus p. 5^3 Not as above 33 33. Lactose fermented; cells pleomorphic; arranged in palisades and chinese-letter forms; frequently bar-shaped, beaded and clubbed Corynebacterium p. 579 Lactose not fermented 31 31. Organisms occur singly, in pairs or in short chains; not pleomorphic Brevibacteriiim p. 490 (See also B. healii) Organisms normally found in palisade or chinese-letter forms, pleomorphic; barred, beaded and club-shaped forms common Corynebacterium p. 579 Note: Criteria for separation of these two genera are inadequate. 35. Organisms produce a true branching mycelium which later disintegrates into simple rods, cocci and rods with remnants of branches Actinomyces p. 7^2 Organisms do not branch or, if branching occurs, it is limited to bifurcations and branching of isolated rods; no true mycelium formed 36 36. Endospores produced 37 No endospores produced 38 37. Organisms reduce CO2 to CH4 while oxidizing secondary alcohols to ketones and primary alcohols to acids Methanobacterium p. 250 {M. omelianskii) Not as above Clostridium p. 634 38. Cells motile; gas produced from peptone in the absence of carbohydrates Cillobacterium p. 566 Note: Glucose and other carbohydrates are fermented by all species; butyric acid is frequently among the byproducts. Cells non-motile 39 39. Visible gas produced in culture media either in the presence or absence of carbohj'drates 40 Note: In the ensuing section of the key, from 40 to 44 inclusive, the statement "acid from" infers "acid" or "acid and gas," since it is not clear whether gas produced in the presence of carbohydrate arises from the fermentation of the sugar or action on the peptone. Visible gas in culture media either in the presence or absence of carbohydrates; glucose fermentation not recorded; pathogenic to guinea pigs; rods occur singly, in pairs, in V-formation, in short chains and in clumps. See Eubacterium niosii and Eubacterium guintum No visible gas produced in culture media in the presence or absence of carbohydrates 45 40. Acid produced from glucose, lactose and fructose 41 Acid produced from glucose and fructose but not from lactose 42
