ganism as a member of the genus Mycococcus on the basis of the resting cells and branch- ing rods; it resembles a tetracoccus on the basis of the characteristic cell groupings. It differs from Mycococcus capsulatus in that the capsules form on practically all media. Source: Isolated from soil of the Quy- bishev Agricultural Institute. Habitat: Infrequently found in soil. 4. Mycococcus luteus Krassilnikov, 1938. (Microbiologia (Russian), 7, Part I, 1938, 349.) lu'te.us. L. adj. luteus yellow. Original description supplemented by material from Krassilnikov (Guide to the Actinomycetes, Izd. Akad. Nauk, U.S.S.R., Moskau, 1941, 217). Cells coccoid, ovoid or irregular, 0.5 to 0.8 micron in diameter, united somewhat into short rods. After 5 to 7 days there are found enlarged, lemon-shaped, spherical cells up to 1.5 microns in diameter; they are later destroyed and disappear. In old cul- tures there are resting cells with thicker protoplasm; they reproduce like the spores of an actinomycete. In liquid media, some strains form individual short rods, 0.7 by 1.0 micron, which branch infrequently. Gelatin: No liquefaction by two strains, weak liquefaction by one. Colonies: Bright yellow, sometimes golden or brown. No soluble pigment. Milk: No coagulation; no peptonization. Sucrose is weakly inverted. Acid from glucose and fructose; no acid from sucrose. Citric and acetic acids are not utilized as sources of carbon. No growth on paraffin. Source: Isolated from soil. Habitat: Infrequently found in soil. 5. Mycococcus flavus Krassilnikov, 1941. (Guide to the Actinomycetes, Izd. Akad. Nauk, U.S.S.R., Moskau, 1941, 127.) fla'vus. L. adj. flavus yellow. Morpholog}^ same as that of Mycococcus luteus. Gelatin: Rapid liquefaction. Colonies: Brownish yellow; no soluble pigment. Milk: Coagulation and peptonization. Acid from glucose. Starch: No hydrolysis. Citric and acetic acids are utilized as sources of carbon. Source: Isolated from soil of Zabolgia, Russia. Habitat: Infrequently found in soil. 6. Mycococcus citreus Krassilnikov, 1938. (Microbiologia (Russian), 7, Part I, 1938, 349.) cit're.us. L. adj. citreus of the citrus tree; M.L. adj. citreus lemon-yellow. Original description supplemented by ma- terial from Krassilnikov (Guide to the Ac- tinomycetes, Izd. Akad. Nauk, U.S.S.R., Moskau, 1941, 127). Cells extremely variable in size: in the same culture are found cells from 0.2 mi- cron and smaller up to 1.0 micron in diameter. Cells are frequently round, single or united into short chains of two or three cells. Protoplasm is light and uniform. Rod forms up to 1.5 microns in length are occa- sionally seen in liquid media; branched forms are observed in hanging drop prepa- rations. Resting forms are found in old cultures. Gelatin: Rapid liquefaction. Colonies: Yellow-green and lemon- colored; smooth; waxy. Milk: Peptonization and coagulation. Sucrose is inverted. Acid from glucose, fructose and sucrose. Nitrites produced from nitrates by most strains. Starch: Active hj^drolysis. No growth on organic acids. No growth on paraffin. Comment: Ten cultures were isolated, all of which differed from each other in in- tensity of pigment and in certain physio- logical properties. Krassilnikov regards these differences as insufficient to separate them into distinct species or even strains. One culture, isolated in the Institute of Microbiology of the Academy of Sciences under the name Micrococcus, was found to be Mycococcus citreus. Source: Isolated from soil. Habitat: Found in soil rather frequently.
