708 



ORDER V. ACTINOMYCETALES 



uber subsp. ietragenus. 



limy capsule. 



aa. Cells frequently united into groups of four 

 2a. Mxjcococcu 

 2. Colonies mucoid and spreading. 



a. Cells occur singly or in short chains; surrounded by a thick 



3. Mycococcus capsulatus. 



aa. Cells occur in groups of four; surrounded by a thin, slimy capsule. 



3a. Mycococcus capsulatus subsp. mucosus. 

 B. Chromogenesis yellow. 



1. Colonies bright yellow or brownish yellow. 



a. Colonies bright yellow; fermentative capacity weak. 



4. Mycococcus luteus. 



aa. Colonies brownish yellow; fermentative capacity strong. 



5. Mycococcus flavus. 



2. Colonies yellow-green or lemon -yellow. 



6 



1. Mycococcus albus Krassilnikov, 1938. 

 (Microbiologia (Russian), 7, Part I, 1938, 

 350.) 



al'bus. L. adj . albus white. 



Original description supplemented by 

 material from Krassilnikov (Guide to the 

 Actinomycetes, Izd. Akad. Nauk, U.S.S.R., 

 Moskau, 1941, 124). 



Cells round or slightly ovoid, 0.7 to 1.0 

 micron in diameter. On some media, such as 

 salt agar, are found rod-shaped cells, 0.7 

 by 1.0 to 1.2 microns, with wide branches. 

 In 2- to 5-day-old cultures there are found 

 large, spherical and lemon-shaped cells up 

 to 1.5 microns in diameter; these frequently 

 form on the surface of the medium when the 

 culture has been seeded upon a fresh sub- 

 strate. There are marked differences be- 

 tween the daughter and mother cells. In 

 old cultures many cells are changed into 

 resting forms. Not acid-fast. Gram-positive. 



Gelatin: Rapid liquefaction. 



Colonies: Well developed on all media; 

 large, moist and shiny. 



Malt agar: Excellent growth; colonies 

 pasty. 



Synthetic agar with sucrose: Excellent 

 growth. 



Glycerol agar: Excellent growth. 



Potato: Good growth by some strains. 



Milk: Coagulated and peptonized. 



Acetic acid and citric acid media: Good 

 growth. 



Sucrose is inverted. 



Acid from glucose and fructose. 



Starch: Good growth; hydrolysis. 



No growth on paraffin. 



Comment: Krassilnikov (loc. cil.) recog- 



Mycococcus citreus. 



nizes two subspecies: Mycococcus albus 

 subsp. albidus, distinctive because of its 

 weak ability to attack substances, and 

 Mycococcus albus subsp. lactis, distinctive 

 because of the way in which it coagulates 

 milk. 



Source: Isolated from soil at Yershovo 

 Station, Russia. 



Habitat: Infrequently found in soil. 



la. Mycococcus albus subsp. albidus Kras- 

 silnikov, 1941. (Guide to the Actinomycetes, 

 Izd. Akad. Nauk, U.S.S.R., Moskau, 1941, 

 124.) 



al'bi.dus. L. adj. albidus white. 



Cells rounded or slightly angular, usually 

 0.6 to 0.7 micron in diameter, occurring 

 singly or in short chains of 3 to 5 cells. Rod- 

 shaped forms and enlarged forms have not 

 been observed. Resting forms, 0.8 micron 

 in diameter, are found in old cultures. 



Gelatin: Weak liquefaction. 



Colonies on solid nutrient media poorly 

 developed; they are white and are smaller, 

 flatter, smoother, more shiny and of a more 

 compact consistency than those of Myco- 

 coccus albus. 



Protein media: Good growth. 



Synthetic agar with sucrose: Good 

 growth. 



Milk: Slow coagulation; weak peptoniza- 

 tion; slightly alkaline. 



No acid from glucose, sucrose or lactose. 



Starch : Hydrolysis slow, forming a narrow 

 zone of not more than 2 mm around the 

 colony. 



Nitrites rapidly produced from nitrates. 



Proteolytic action weak. 



Comment: One culture (No. 25), after a 



