FAMILY XII. CORYNEBACTERIACEAE 



Rods, 0.5 to 1.0 by 1.0 to 4.0 microns, 

 which may be curved or club-shaped; oc- 

 casionally rudimentary filamentous forms 

 maj' occur, although branching is infre- 

 quent. The longer forms fragment into short 

 rods and cocci. Cells in older cultures are 

 almost exclusively coccoid and vary from 

 1.0 to 3.0 microns in diameter. When trans- 

 ferred to fresh media, the larger coccoid 

 cells (cystites) germinate, giving rise to one 

 or two rod-shaped cells (Sguros, Jour. Bact., 

 69, 1955, 28). Non-motile. Gram-negative; 

 the cystites are Gram-negative and usually 

 possess a Gram-positive granule. 



Gelatin stab: Slow, crateriform liquefac- 

 tion. 



Agar colonies: Punctiform or circular, 

 convex, opaque, smooth, glistening; viscid 

 or butj'rous varieties may occur. 



Agar slant: Growth abundant, filiform, 

 opaque, smooth, glistening; yellow and 

 pearl-gray strains occur, the former being 

 viscid and the latter butyrous in consist- 

 ency. 



Asparagine agar: Growth filiform, opaque, 

 smooth, glistening; development of chromo- 

 genesis retarded. 



Nicotine agar: Abundant growth with the 

 production of a diffusible, deep blue pigment 

 which turns reddish to yellowish brown with 

 age. 



Broth: Abundant growth; surface ring; 

 viscid sediment. 



Potato: Abundant growth, yellow to gray 

 varying with the strain. 



Milk: Slow peptonization and reduction 

 of litmus; reaction alkaline. 



Indole not produced. 



Hydrogen sulfide not produced. 



Acid but no gas from fructose and su- 

 crose; acid in glucose broth weak and tran- 

 sient; with other carbohydrates, reaction 

 alkaline. 



Acetylmethylcarbinol not produced. 



Starch is hydrolyzed. 



Nitrites produced from nitrates. 



Utilizes nitrates and ammonium salts as 

 nitrogen sources; citrates utilized as sole 

 source of carbon. 



Catalase-positive. 



Aerobic. 



Optimum temperature, 25° C. 



Comment: Yellow-viscid and pearl -white- 



butyrous biotypes of this species have been 

 recognized (Sguros, loc. cit.). 



Source: Isolated from tobacco leaves. 



Habitat: Probably soil. 



5. Arthrobacter aurescens (Clark, 1951) 

 Phillips, 1953. (Arthrobacter globifonne var. 

 aurescens Clark, Proc. Soil Sci. Soc. Amer., 

 15, 1951, 180; Phillips, Iowa State Coll. Jour. 

 Sci., 27, 1953, 240.) 



au.res'cens. L. v. auresco to become 

 golden; L. part. adj. aurescens becoming 

 golden. 



Rods which vary in shape and size accord- 

 ing to the nature of the culture medium: 

 0.5 by 1.0 to 3.0 microns on plain agar and 

 0.6 to 0.8 by 1.0 to 6.0 microns on enriched 

 solid media; the cells may be straight, 

 curved or swollen or may show rudimentary 

 branching, especially in enriched liquid 

 media. In older cultures the cells become 

 coccoid, measuring 0.6 micron in diameter. 

 Non-motile. Gram-variable; the cocci are 

 generally Gram-negative although the 

 larger coccoids (cystites) are usually Gram- 

 positive. 



Gelatin stab: Stratiform liquefaction; 

 yellowish surface growth; moderate sedi- 

 ment; liquid very turbid. 



Agar colonies: Circular, up to 2 mm in 

 diameter, convex, yellow, opaque, smooth, 

 glistening. 



Agar slant: Growth abundant, filiform, 

 opaque, smooth, creamy lemon-yellow, soft, 

 waxy luster with a metallic sheen. 



Soil-extract agar slant: Growth filiform, 

 smooth, cream-colored becoming pale yel- 

 low, glistening, soft. 



Asparagine agar slant: Growth filiform, 

 lemon-yellow, soft, waxy luster; surface 

 uneven; edge finely indented. 



Nicotine agar: Growth slow and sparse, 

 flat, translucent, colorless. 



Broth: Moderately turbid; no surface 

 growth; considerable cream-colored sedi- 

 ment. 



Potato: Growth moderate, brownish yel- 

 low, dull, cheesy in consistency. 



Milk : Pale yellow surface and ring growth ; 

 clearing (3 to 4 daj's) without coagulation; 

 cream-colored sediment. 



Indole not produced. 



