Rods, usually slightly thinner, in long chains twisted together to form strands. Agar colonies: Grayish, thin, widely spreading by means of long, twisted chains of cells, turning to the left or right (sinistral or dextral). The sinistral form occurs more often in soil (Gause, Mikrobiologia, 18, 1949, 154). Agar slants: Growth thin, rhizoid, gray- ish, widely spreading, adhering to or grow- ing into the agar. With aging, growth be- comes thicker and softer. Gordon (Jour. Bact., 39, 1940, 98) and Smith, Gordon and Clark (op. cit., 1952) showed that Bacillus mycoides lost its rhi- zoid character if grown from a small inocu- lum in flasks containing 100 ml of broth and plated on agar after 3 to 30 days. The result- ing non-rhizoid cultures could not be differ- entiated from Bacillus cereus. Dissociation occurred under other conditions, but not so rapidly or completely. Reversion to the rhizoid state was not observed, although the dissociants were grown under a variety of conditions intended to induce such re- version. Source: Isolated from soil. Habitat: Widely distributed in soil. 3. Bacillus anthracis Cohn, 1872, emend. Koch, 1876. (Les infusories de la maladie charbonneuse, Davaine, Compt. rend. Acad. Sci., Paris, 69, 1864, 393; Cohn, Beitrage z. Biol. d. Pflanzen, ^, Heft 2, 1872, 177; Koch, ibid., 2, Heft 2, 1876, 279; Bac- teridie des charbon, Pasteur and Joubert, Compt. rend. Acad. Sci., Paris, 84, 1877, 900.) an'thra.cis. Gr. noun anthrax charcoal, a red precious stone, a carbuncle; M.L. noun anthrax the disease anthrax; M.L. gen.noun anthracis of anthrax. Rods, 1.0 to 1.3 by 3.0 to 10.0 microns, with square or concave ends, occurring in long chains; resemble Bacillus cereus. When lightly stained, protoplasm granular or foamy. Encapsulated. Non-motile. Gram- positive. Spores ellipsoidal to cylindrical, 0.8 to 1.0 by 1.3 to 1.5 microns, central or para- central, often in chains. Germination polar. Sporangia ellipsoidal to cylindrical, not definitely swollen, in chains. Gelatin stab: Arborescent in depth, in- verted pine tree. Liquefaction crateriform becoming stratiform. Gelatin agar streak plate: Wide zone of hydrolysis. Agar colonies: Large, dense, irregular, composed of parallel chains of cells giving a curled or combed appearance; similar to certain strains of Bacillus cereus. Agar slants : Growth abundant, spreading, dense, grayish, with irregular borders. Blood hemolysis : Variable (Bekker, Zent. f. Bakt., I Abt., Orig., I47, 1941, 451; also see ibid., 150, 1943, 326). Broth: Little or no turbidity; thick pel- licle. Milk: Coagulated, slightly acid, pep- tonized. Milk agar streak plate: Wide zone of hy- drolysis of the casein. Potato: Growth abundant, spreading, white to creamy. Acid but no gas (with ammonium salts as source of nitrogen) from glucose, fruc- tose, sucrose, maltose, trehalose and dex- trin. Late and slight acidity from glycerol and salicin by some strains. No acid from arabinose, rhamnose, mannose, galactose, lactose, rafEnose, inulin, mannitol, dulcitol, sorbitol, inositol or adonitol. Starch hydrolyzed. Acetylmethylcarbinol produced. Nitrites produced from nitrates. Amino acids are necessary for growth. Lecithinase produced. Aerobic, facultatively anaerobic. Temperature relations: Optimum, about 35° C. Maximum, about 43° C. Pathogenicity: Cause of anthrax in man, cattle, swine, sheep, rabbits, guinea pigs, mice, etc. (Smith, Gordon and Clark {op. cit., 1952) considered Bacillus anthracis as a pathogenic variety of Bacillus cereus be- cause certain strains of the two were in close agreement in all characters except patho- genicity. As strains of Bacillus anthracis may become avirulent, and as certain strains of Bacillus cereus may be lethal in massive dosages (Clark, Jour. Bact., 33, 1937, 435), the relationship is closer than most investi- gators realize.)
