COMPREHENSIVE KEY 1017 



24. Curved and irregular cells; may branch in young cultures; capable of using phenolic 



compounds as the sole source of carbon; gas, presumably nitrogen, produced in 0.1 

 per cent nitrate broth but no nitrites are produced; no acid from carbohydrates 



Mycoplana p. 304 

 Not as above 25 



25. Curved rods, very small, about 1.0 micron in length, which, during growth, produce 



closed rings, 2.0 to 3.0 microns in diameter, which later change to two horseshoe- 

 shaped halves fastened together without any evidence of divisional lines. These 

 divide into separate rods which reproduce the cycle; encapsulated; grow well in 



0.5 per cent peptone water Microcyclus p. 25S 



Not as above 26 



26. Curved or S-shaped rods, 0.1 to 0.2 bj' 6 to 8 microns or longer; very poor growth on 



peptone agar; 



or 

 short straight rods 0.5 by 1 to 2 microns; good growth on peptone agar; on inorganic 

 thiosulfate agar, small watery colonies produced which turn white from the deposi- 

 tion of sulfur; grow autotrophically, oxidizing thiosulfate to sulfur and sulfate 



Thiobacillus p. 83 

 Not as above 27 



27. Curved cells, 1 by 5 to 10 microns, which form chains which may twist around each 



other to form coiled, non-septate, non-motile colorless bundles; enclosed in a spheri- 

 cal, solid gelatinous mass from 10 to 17 microns in diameter; found floating on water 



containing decomposing plant material Myconostoc p. 260 



Not as above 28 



28. Curved organisms which grow on precipitated-cellulose mineral-salts agar producing 



a clearing of the medium around the colonies; also grow in 0.5 per cent peptone 

 water in which a strip of filter paper is half immersed, weakening the filter paper 

 sufficiently for the fibers to separate on slight agitation or reducing it to a pulpy 

 mass; organisms are arranged in palisade fashion similar to the corj^nebacteria 



Cellulomonas p. 601 

 (See also Vibrio agarliquefaciens and V. fuscus.) 

 Not as above 29 



29. Curved organisms which grow on a filter-paper mineral-salts medium oxidizing the 



cellulose to oxycellulose 30 



Not as above 31 



30. Sickle-shaped; cells no longer than 2.0 microns; stain more intensely at the center than 



at the ends; no growth on a mineral salts agar containing starch; green, cream or 



brownish on filter paper Cellfalcicula p. 252 



Curved cells 1.5 to 5.0 microns in length, with rounded ends; grow moderately well on 

 mineral salts agar containing starch; cream, brown or no pigment on filter paper 



Cellvibrio p. 250 



31. Curved rods which transform completely into coccoid forms during growth of the 



colony. Rods elongate and divide. At the point of division the rods grow out at an 

 angle to the original axis and divide again at the angle when the cell has doubled its 

 length. This process continues until a colony is formed. Ultimately the rods trans- 

 form completely into cocci Arthrobacter p. 605 



Note: The emphasis lies on the final transformation into cocci. Some authori- 

 ties may consider that limited true branching may occur. If this is admitted, 

 the dividing line between Arthrobacter and Nocardia becomes very slim. The 

 author's observations of Arthrobacter globiforme fit the above statement, and it 

 is suggested that these criteria be adopted, true branching forms which later 

 disintegrate being assigned to Nocardia. 

 Not as above 32 



