oped colonies are transparent with a bluish sheen by reflected light, circular and entire. Tellurite agar colonies: Grayish and pin- point in 24 hours, later increasing in size and becoming jet black. Broth: Slight turbidity with scant, gray- ish sediment. Litmus milk: No change. Indole not produced. Hj^drogen sulfide produced. Blood serum shows scant growth. No gas from carbohydrates. Acid from glucose, galactose, fructose and lactose. When the basic medium is very favorable, acid may be produced from xy- lose, arabinose, mannose, maltose, cello- biose and melibiose. Usually no acid from glycerol, sorbitol, mannitol, inositol, rham- nose, sucrose, trehalose, melezitose, raffi- nose, starch, inulin or salicin. The addition of yeast autolysate to media for fermenta- tion studies is recommended. Esculin not hydrolyzed. Final pH in yeast extract trj^pticase-glu- cose broth usually about 6. Blood agar: On prolonged incubation there is at first a greening and then a slight but definite clearing around the colonies. Nitrites not produced from nitrates. Catalase-negative. Facultatively anaerobic. Temperature range of growth, 16° to 41° C. The fastest growth rate is at about 37° C. The maximum cell crop is obtained near 33° C. Optimum pH, between 7.4 and 7.8. Tolerates phenol in concentrations to 0.2 per cent and potassium tellurite in concen- trations to 0.05 per cent. Source: Isolated from cases of swine ery- sipelas, human erysipeloid and mouse sep- ticemia; also isolated from infections in birds, e.g. turkeys and ducks. Transmissible to a large number of experimental animals : pigeons and mice are susceptible to experi- mental infection, but rabbits are less sus- ceptible, and guinea pigs are quite resist- ant; inoculation in man has been successful; susceptibility of swine is very variable. Fish handlers are especially subject to erysipe- loid infections derived from fish (Bedford and Leeds, Brit. Jour. Dermat. and Syph., U, 1932, 368; Niewiarowski, see Biol. Abst.,
- g7, 1953, No. 17069).
Habitat : This organism is widely distrib- uted in nature as indicated above. Genus IV. Microbacterium Orla-Jensen, 1919.* (The Lactic Acid Bacteria, 1919, 179.) Micro. bac.te'ri.um. Gr. adj. micrus small; Gr. neut.dim.n. hactcrium a small rod; M.L. neut.n. Microbacterium a small rodlet. Small rods with rounded ends; vary in length from 0.5 to 30 microns. Non-motile. Gran- ulations demonstrable with methylene blue stain. Gram-positive. Good surface growth on media supplemented with milk or yeast extract. Acid production weak with principally L (+)- lactic acid produced from fermented carbohydrates. Catalase-positive. Optimum temperature, 32° C. Thermoduric saprophytes found chiefly in dairy products and on utensils. The type species is Microbacterium lacticum Orla-Jensen. Key to the species of genus Microbacterium. I. Hydrolyzes starch; produces acid from maltose. 1. Microbacterium lacticum. II. Does not hydrolj^ze starch; acid not produced from maltose. 2. Microbacterium flavum. 1. Microbacterium lacticum Orla-Jen- sen, 1919. (The Lactic Acid Bacteria, 1919, 179.) lac'ti.cum. L. mas.n. lac, lactis milk; M.L. adj. lacticxis pertaining to milk, lactic. Small, diphtheroid rods, 0.4 to 0.7 by 1.0 Revised by Dr. R. N. Doetsch, University of Maryland, College Park, Maryland, April, 1953.
