Hydrogen sulfide produced in cysteine and thiosulfate media. Sugar media: Very slight acidity from glucose and sucrose; no gas from carbohy- drates. Acetylmethylcarbinol not produced. Starch is hydrolyzed. Nitrites produced from nitrates. Urease not produced. Utilizes nitrates and ammonium salts as nitrogen sources; citrates utilized as sole carbon source. Catalase-positive. Aerobic, facultatively anaerobic. Temperature relations: Optimum, be- tween 20° and 32° C; slight growth at 10° and at 37° C; no growth at 45° C. Source: Isolated from soil by Conn and Dimmick (Soil Sci., 65, 1948, 349). Cultures of yellow forms were labelled Arthrobacter aurescens and were distributed to other investigators under this name. Habitat: Soil. 6. Arthrobacter ureafaciens (Krebs and Eggleston, 1939) Clark, 1955. (Culture NC, Dubos and Miller, Jour. Biol. Chem., 121, 1937, 431; Krebs and Eggleston, En- zymologia, 7, 1939, 310; Corynebacterium creatinovorans , name used by Dubos on Cul- ture NC (ATCC No. 7562) as sent to Amer. Type Culture Coll., December, 1941, and used in the Catalogue of Cultures, 1949, and later in the literature by various authors such as Kalinsky, Proc. Soc. Exp. Biol, and Med., 7J^, 1950, 767, and Barron, Ardac and Hearson, Arch. Biochem., 29, 1950, 130; Clark, Internat. Bull, of Bact. Nomen. andTaxon.,5, 1955, HI; also see Bact. Rev., 19, 1955, 273.) u.re.a.fa'ci.ens. Gr. noun urum urine; M.L. noun urea urea; L. v. jacio to make, produce; M.L. part. adj. ureafaciens urea- producing. Rods which vary in shape and size accord- ing to the nature of the culture medium: in young cultures, 0.5 by 1.0 to 3.0 microns on plain agar and 0.7 by 2.0 to 7.0 microns on richer media; the cells are irregular and may be curved, bent or swollen. In older cultures the cells are cocci and coccoid rods, measuring 0.6 by 0.8 micron. Non-motile. The rods and cocci are Gram-negative. Gelatin stab: Stratiform liquefaction; cream-colored surface growth; liquid slightly turbid and flaky. Sediment is abun- dant. Agar colonies: Circular, 1.5 to 2.0 mm in diameter, convex, yellow, smooth, glisten- ing. Agar slant: Growth moderate, filiform, yellow, glistening with a metallic sheen, soft; surface uneven, becoming wrinkled. Soil-extract agar slant: Growth filiform, pale gray becoming yellow, glistening, soft; surface uneven; edge finely wrinkled. Asparagine agar slant: Growth filiform, lemon-yellow, glistening, soft; surface un- even; edge becoming wrinkled. Broth: Moderately turbid; no surface growth; cream-colored sediment. Potato: Growth moderate, raised, yellow- ish brown, dull, cheesy in consistency. Milk: Flaky, yellowish surface growth; clearing without coagulation; cream-colored sediment. Indole not produced. Hydrogen sulfide produced in cysteine media. Sugar media: Little or no acidity; no gas. Acetjdmethylcarbinol not produced. Starch is not hydrolj^zed. Nitrites not produced from nitrates. Urea produced from creatine, creatinine and uric acid. Urease not produced. Utilizes nitrates and ammonium salts as nitrogen sources. Catalase-positive. Aerobic. Temperature relations: Optimum, 32° C. No growth at 10° or at 45° C. Good growth between 25° and 37° C. Source: Isolated from soil. Habitat: Soil. 7. Arthrobacter tumescens (Jensen, 1934) Conn and Dimmick, 1947. {Corynebac- terium tumescens Jensen, Proc. Linn. Soc. New So. Wales, 59, 1934, 45; Conn and Dim- mick, Jour. Bact., 54, 1947, 295, Fig. 3, and 302.) tu.mes'cens. L. part. adj. tumescens swell- ing up. Rods, 0.5 to 0.8 by 2.0 to 6.0 microns, oc- curring in an angular arrangement and
