Bact., 46, 1943, 12) describe a variety of this species from the feces and intestinal con- tents of guinea pigs. Source : Isolated from the feces of milk-fed infants. Also found in the feces of older persons on high milk-, lactose- or dextrin- containing diets. Habitat: Same as for the source. 5. Lactobacillus bifidus (Tissier, 1900) Holland, 1920. (Bacillus bifidus communis and Bacillus bifidus Tissier, Recherches sur la flore intestinal des nourrissons, Paris, 1900, 85; Holland, Jour. Bact., 5, 1920, 223.) bi'fi.dus. L. adj. bifidus cleft, divided. Description supplemented from Weiss and Rettger (Jour. Bact., 28, 1934, 501). Small, slender rods, the average length of which is 4.0 microns, 0.5 to 0.7 by 2 to 8 microns (Weiss and Rettger), occurring singly or in pairs and short chains, parallel to each other, very variable in appearance. Branched and club forms develop in some cultures. Non-motile. Gram-positive but stains irregularly in old cultures (Tissier). Little or no growth in carbohydrate-free agar (Weiss and Rettger). Deep sugar-agar colonies: After 3 days, solid with slightly irregular edge, whitish. Grow up to 3 cm from the surface forming a ring. Average diameter 3 mm. No gas. Sugar broth: Good growth. Turbid within 3 days. Clears with fiocculent precipitate. Milk: Good growth with large inoculum. No coagulation (Tissier). May or may not coagulate milk (Weiss and Rettger). Acid but no gas from glucose (Tissier). Acid from glucose, fructose, galactose, su- crose, inulin and usually from dextrin, starch, maltose, raffinose and trehalose. A few strains form acid from lactose and sali- cin. The acid consists of optically inactive lactic acid and 18 to 25 per cent of volatile acid (Weiss and Rettger). Orla-Jensen (The Lactic Acid Bacteria, 1919, 192), Eggerth (Jour. Bact., 30, 1935, 295) and Weiss and Rettger (Jour. Bact., 85, 1938, 17; Jour. Inf. Dis., 62, 1938, 115) describe a more anaerobic variety of this species which produces more volatile acid as well as dextro rotatory lactic acid and which ferments arabinose, xylose and melezitose but not mannose. Strict anaerobe (Tissier). Strict anaerobe in primary culture, becoming microaero- philic (Weiss and Rettger). Optimum temperature, 37° C. May show slight growth at 20° C. Killed at 60° C. in 15 minutes. Non-pathogenic for mice or guinea pigs. Distinctive characters: Bifurcations and club-shaped forms (Tissier), particularly in infant feces and in primary culture (Weiss and Rettger). Comment: A variety of this species that grows more readily in human than in cow's milk is discussed by Gyorgy and Rose (Jour. Bact., 69, 1955, 483) and in papers listed in the bibliography of this report. This differ- ence appears to be due to a specific growth factor, the so-called bifidus factor. Source: Isolated from feces of nursing infants. Habitat: Very common in the feces of infants. May constitute almost the entire intestinal flora of breast-fed infants. Also present in smaller numbers with bottle-fed infants. Possibly more widely distributed than indicated in the intestines of warm- blooded animals. 6. Lactobacillus biilgaricus (Luerssen and Kiihn, 1907) Holland, 1920. {Bacillus A, Grigoroff, Revue M6d. Suisse romande, 25, 1905; Bacillus biilgaricus Luerssen and Kuhn, Cent. f. Bakt., II Abt., 20, 1907, 241; Holland, Jour. Bact., 5, 1920, 215.) bul.ga'ri.cus. M.L. adj. bulgaricus Bul- garian. Description of Luerssen and Kiihn sup- plemented by Grigoroff {op. cit., 1905), Co- hendy (Compt. rend. Soc. Biol. Paris, 58, 1906, 364), Kuntze (Cent. f. Bakt., II Abt., 21, 1908, 737), Bertrand and Duchacek (Ann. Inst. Past., 23, 1909, 402), White and Avery (Cent. f. Bakt., II Abt., 25, 1910, 161), Rahe (Jour. Bact., 3, 1918, 420), Orla-Jensen (The Lactic Acid Bacteria, 1919, 164), Kulp and Rettger (Jour. Bact., 9, 1924, 357) and Sher- man and Hodge (Jour. Dairy Sci., 19, 1936, 494). Slender rods with rounded ends, often in chains. Non-motile. Gram-positive, older cultures showing unstained portions (Lu- erssen and Kiihn). Whey gelatin: No liquefaction (White and Avery).
