612 



ORDER IV. EUBACTERIALES 



ter're.gens. L. noun terra soil; L. part. adj. 

 egens requiring; M.L. part. adj. terregens 

 soil-requiring. 



Rods, 0.6 to 0.8 by 1.0 to 5.0 microns, usu- 

 all}^ occurring in V-shaped pairs as a result 

 of snapping division. The cells vary in shape 

 from short, straight rods to irregular, curved 

 or swollen forms; some of the longer rods 

 show rudimentary budding. In older cul- 

 tures (usually after 3 days), coccoid cells, 

 formed by the fragmentation of long rods, 

 predominate. The cocci vary in size accord- 

 ing to the medium: on soil extract agar the 

 cells measure 0.6 to 0.7 micron, and on 

 richer media containing yeast extract, they 

 are 0.8 to 0.9 micron in diameter. When 

 freshl}^ transferred, the larger coccoids 

 (cystites) may germinate rod forms, up to 

 three in number. Gram-negative; the coc- 

 coid cells are Gram-variable, usually Gram- 

 negative. 



Requires a growth factor, 'terregens fac- 

 tor' (TF), present in soil extract or in cul- 

 ture filtrates of Arthrobacter pascens. No 

 growth in standard media; these may be 

 rendered suitable for growth by addition of 

 soil extract or culture filtrate of A . pascens. 



Gelatin stab: Yellowish growth, best at 

 surface; no liquefaction. 



Agar colonies: Circular, 1.0 to 2.5 mm in 



diameter, entire, convex, yellowish brown, 

 glistening. 



Agar slant: Growth filiform, flat, pale 

 brown, glistening. 



Soil extract agar slant: Growth filiform, 

 flat, yellowish brown, glistening, soft; sur- 

 face finely roughened. 



Broth: Moderately turbid; no surface 

 growth; stringy, yellowish sediment. 



Potato: Slight or no growth. 



Milk: No change after 6 weeks. 



Indole not produced. 



Hydrogen sulfide not produced. 



Slight acid from glucose and sucrose; 

 trace or no acid from other sugars; no gas 

 produced. 



Acetylmethylcarbinol not produced. 



Starch not hydrolyzed. 



Nitrites produced from nitrates. 



Urease not produced. 



Unable to utilize nitrates or ammonium 

 salts as nitrogen source, or citrates as sole 

 carbon source, even in presence of growth 

 factor. 



Catalase-positive. 



Aerobic. 



Optimum temperature, between 20° and 

 26° C.; grows from 15° to 35° C.; no growth 

 at 10° or 37° C. 



Source: Isolated from soil. 



Habitat: Soil. 



