1. Bacillus megaleriuni de Bary, 1S84. (DeBary, Vergleichende Morph. und Biol, der Pilze, 1884, 499; Bacillus megatherium (sic) Schroeter, in Cohn, Kryptogamen- Flora V. Schlesien, 3, 1, 1886 (1889), 160.) me.ga.te'ri.um. Gr. adj. mega large; Gr. noun teras, teratis monster, beast; M.L. noun megaterium big beast. The second stem has been claimed to be a faulty trans- literation of the Gr. noun therium an animal. The Judicial Commission of the Interna- tional Committee on Bacteriological No- menclature has ruled, however, that the original spelling is to be preferred (Internat. Bull. Bact. Nomen. and Taxon., 1, 1951, 35). Rods, 1.2 to 1.5 by 2.0 to 4.0 microns, with rounded ends, occurring singly or in short chains. When lightly stained, protoplasm granular or foamy. Occasional shadow- or ghost-forms. Motile. Gram-positive. Vari- ations: 0.9 to 2.2 by 1.0 to 5.0 microns, oc- curring in filaments or long and tangled chains. Ends square. Protoplasm evenly stained. Many shadow-forms. Buds at end or side of rods. Non-motile. Gram-var- iable. On glucose agar, rods are usually larger, longer and more vacuolated because of numerous, large, fat globules, sometimes irregular in shape with pointed ends or corkscrew-shaped (in wet mount) . Spores, 1.0 to 1.2 by 1.5 to 2.0 microns, ellipsoidal, central to para-central. Thin- walled. Many formed in 48 hours. Varia- tions: Diameters 0.8 to 1.4 microns. Shapes are irregular, reniform, oviform, almost spherical and cylindrical. Lateral. Only a few are formed in 3 to 6 days. Sporangia not distinctly swollen. Gelatin stab: Slow liquefaction. Gelatin agar streak plate: Wide zone of hydrolysis. Agar colonies: Large, smooth, soft, glis- tening, round, convex, entire, non-spread- ing, dense, creamy white to yellow. Varia- tions: Rough, concentrically or radially ridged, thin edged. Agar slants: Growth abundant, smooth, soft to butyrous, opaque, glistening, slightly spreading, non-adherent, creamy white to yellow. Some browning with pellucid dots on aging. Variations: Rough, slightly wrin- kled, tough, adherent, non-spreading. Glucose agar slants: Growth usually more abundant and softer (somewhat slimy) than on agar. Variations : Gummy, coarsely wrin- kled. Pellucid dots more distinct than on agar. Glucose nitrate agar slants: Growth very heavy, raised. Soybean agar slants: Growth abundant. Better sporulation and fewer shadow-forms than on agar. Tyrosine agar slants: Deep black pigment b}^ few strains. Broth: Turbidity medium to heavy, uni- form, with or without abundant sediment. No pellicle. Variations: Turbidity flocculent or granular. Pellicle thin and friable. Broth clear with flocculent sediment. Milk: Peptonized. Milk agar streak plate : Wide zone of hy- drolysis of the casein. Potato: Growth abundant, smooth, soft to slimy, glistening, spreading, creamy white, pale to lemon-yellow or pink. Vari- ations: Rough, wrinkled. Potato blackened or orange-colored. No growth. Acid but no gas (with ammonium salts as source of nitrogen) from glucose, sucrose and mannitol. Acid usually produced from arabinose, xylose and glycerol. Acid pro- duction variable from lactose. Starch hydrolyzed. Acetylmethylcarbinol not produced. Citrates utilized as sole source of carbon. Nitrites usually not produced from ni- trates. No gas from nitrates under anaerobic conditions. Growth factors not essential.* Lecithinase not produced. f Aerobic. No growth in glucose broth under anaerobic conditions. Temperature relations: Optimum, be-
- Information on the nutritional requirements of this as well as of the succeeding species
was supplied by Knight and Proom (Jour. Gen. Microbiol., 4, 1950, 508). t The lecithinase reaction of this and succeeding species was reported by Colmer (Jour. Bact., 55, 1948, 777), McGaughey and Chu (Jour. Gen. Microbiol., 2, 1948, 334) and Knight and Proom {op. cit., 1950, 508).
