igig] DRECHSLER— ACTINOMYCES 157 



ACTINOMYCES XII 



A. aureus Waksman and Curtis 



Cultural characters. — On glucose agar, nutritive mycelium 

 yellowish on reverse side; aerial mycelium changing from white to 

 pale yellowish gray; soluble stain absent. On potato agar, nutri- 

 tive mycelium darker on reverse side; aerial mycelium more 

 profuse, forming a somewhat more deeply colored felty layer; 

 tyrosinase reaction moderate. Identity with Actinomyces aureus 

 established by comparison with authentic material of the latter. 



Morphology. — In this species long prostrate filaments termi- 

 nate in more or less erect fructifications. Secondary branches are 

 proliferated from the lateral elements, generally in successive 

 sequence. A more or less pronounced cuneate thickening of the 

 hyphae below the insertion of a branch is characteristic of the 

 species. The ellipsoidal, uninucleated spores, o . 5-0 .7X0. 8-1 . 2 n, 

 are formed by the insertion of conspicuous septa in open, sinistrorse 

 spirals of 2-7 turns, 3.0-4.PJU in diameter. 



Isolated twice from soil collected in Cambridge, Massachusetts. 



ACTINOMYCES XIII 



Cultural characters. — On glucose agar, nutritive mycelium 

 light orange-brown, the separate individuals fused into a massive 

 pellicle with a depressed, crimped margin. On potato agar, nutri- 

 tive mycelium dark chocolate-brown, wrinkled, lichenoid, secret- 

 ing a diffusible red pigment; t>Tosinase reaction absent. Aerial 

 mycelium on both substrata loose, cottony; developing slowly, 

 first white, later changing to a dull bluish tint. 



Morphology. — The aerial mycehum consists of extremely long 

 filaments, which rarely show any evidence of branching (figs. 74 

 75), and toward their terminations follow an undulating or slightly 

 spiral course. Sporulation occurs as the result of protoplasmic 

 contractions without the appearance of visible septa, the chains of 

 cylindrical spores, 0.4X1 .2-1 .6 /x, being held together for some 

 time by the evacuated portions of hyphal wall, that seem to undergo 

 no apparent constriction. 



Isolated 3 times from soil collected in Cambridge, Massachusetts. 



