Colonies: Flat, yellowish white, 2 to 3 mm in diameter. Old cultures have dark centers. Deep colonies globular (Luerssen and Kiihn). Whey agar colonies: Circular to irregular (White and Avery). Milk: Coagulation at 37° C. No gas. No decomposition of casein. Potato: Yellow-white colonies (Luerssen and Kiihn). No growth (Grigoroff), (Co- hendy), (White and Avery). Indole not produced (Grigoroff), (White and Avery). Results on acid production from sugars vary. Glucose, lactose and galactose are apparently always fermented while xylose, arabinose, sorbose, rhamnose, dulcitol, mannitol, dextrin, inulin and starch are never fermented. Early workers (GigorofT) (Cohendy) noted fermentation of fructose, maltose and sucrose. Later workers (Ber- trand and Duchacek), (Orla-Jensen), (Rahe), (Kulp and Rettger), (Sherman and Hodge) noted variable or negative results on sucrose, maltose and unheated fructose. Forms high acidity in milk. The lactic acid is optically inactive (Grigoroff), (Ber- trand and Duchacek), (White and Avery) or levo rotatory (White and Avery), (Orla- Jensen) with small quantities of volatile acid (White and Avery). Nitrites not produced from nitrates. Aerobic or anaerobic (Luerssen and Kiihn). Microaerophilic (White and Avery). Anaerobic in fresh isolation (Sherman and Hodge). Temperature relations: Optimum, be- tween 45° and 50° C. Minimum, 22° C. (Lu- erssen and Kiihn). Distinctive characters: This species at present is regarded as including the high- temperature organisms isolated from milk with difficulty. These ferment glucose, ga- lactose and lactose but usually do not fer- ment sucrose, maltose or unheated fructose when freshly isolated. Source: Originally isolated from yogurt. Habitat: Probably present in many milk products if held at high temperature. 7. Lactobacillus iherniophilus Ayers and Johnson, 1924. (Jour. Bact., 9, 1924, 291.) ther.mo'phi.lus. Gr. noun therme heat; Gr. adj. philus loving; M.L. adj. thermo- philus heat -loving. Description of Ayers and Johnson sup- plemented by material from Charlton (Jour. Dairy Sci., 15, 1932, 393). Rods 0.5 b}- 3.0 microns. Non-motile (Charlton). Stain irregularly. Gram-posi- tive. Gelatin stab: No liquefaction. Agar plate: Small colonies. Agar slant: Slight, translucent growth (Charlton). Broth: Turbid (Charlton). Litmus milk: Acid. Acid from glucose, lactose, sucrose, starch and trace from glycerol; no acid from sali- cin, mannitol, raffinose or inulin (Ayers and Johnson). Acid from fructose, galactose, mannose, maltose, raffinose and dextrin; no acid from arabinose, xylose, glycerol, rhamnose, salicin, inulin or mannitol. Dex- tro rotatory lactic acid formed (Charlton). Nitrites not produced from nitrates (Charlton). Facultatively anaerobic. Grows best aer- obically. Temperature relations: Optimum, be- tween 50° and 62.8° C. Minimum, 30° C. Maximum, 65° C. Thermal death point, 71° C. for 30 minutes or 82° C. for 2^ min- utes. This is the thermophilic lactobacillus ob- tained from pasteurized milk which causes pin-point colonies on agar plates. Source: Isolated from pasteurized milk. Habitat: Known only from pasteurized milk. 8. Lactobacillus delbrueckii (Leich- mann, 1896) Beijerinck, 1901. {Bacilhis del- hriickii Leichmann, Cent. f. Bakt., II Abt., 2, 1896, 284; Beijerinck, Arch, n^erl. d. sci. exact, et nat., Hadrlem, S4r. 2, 7, 1901, 212.) del.bruec'ki.i. M.L. gen. noun delbrueckii of Delbriick; named for Prof. M. Delbriick, a German bacteriologist. Description of Leichmann supplemented by material from Henneberg (Cent. f. Bakt., II Abt., 11, 1903, 154). Rods, 0.5 to 0.8 by 2.0 to 9.0 microns (Hen- neberg), occurring singly and in short chains. Non-motile. Gram-positive.
