Chapter III — 57 — Morphology 



The cylindrical oidinspores may swell, giving rise to spherical bodies. 

 This manner of sporulation is characteristic of the genus Nocardia and 

 of certain species of Strcptomyces. 



Drechsler recognized three types of sporulation: (a) by means of 

 true fragmentation, (/?) by means of doubling of the cell wall, (c) by 

 means of contractions similar to segmentation. According to DucHE, 

 the last process alone results in the production of three types of spores: 

 (fi) regular and irregular arthrospores, (I?) microarthrospores, produced 

 in the substrate mycelium, and (c) endospores in the aerial mycelium. 

 The true conidia or fragmentation spores are formed only in the aerial 

 mycelium, whereas the vegetative mycelium gives rise to chlamydospores 

 or arthrospores. 



These chlamydospores are produced by the concentration of the 

 plasma in the substrate mycelium and are abundant in some species. 

 They are spherical spores (1.5-1.7[j,), v\ath thick plasma, and are sepa- 

 rated from the rest of the hyphae by cross walls. They are distin- 

 guished from involution forms by a thicker, light-reflecting plasma. 

 They are not produced readily on protein media. 



Spiral formation.— The sporophores in the aerial mycelium are either 

 straight or spiral-forming. The manner of spiral formation is described 

 in detail by Krassilnikov (236). The spirals in the mycelium curve 

 not long before the spores are produced; the branch may be curved 

 completely or only at the end. The number of turns varies in accord- 

 ance with the length of the spiral. There may be as many as 15 or as 

 few as 1 to 3 turns; usually there are 5 to 6. Some species are char- 

 acterized by long spirals and others by short spirals, some by compact 

 and others by extended spirals. The curvature of the branches may 

 be clockwise (dextrorse) or counterclockwise (sinistrorse). Drechs- 

 ler considered the manner of spiral curvature as characteristic of the 

 species. Since certain species show both types of curvature in the same 

 culture, this distinction can hardly be accepted. 



Not all the aerial hyphae give rise to spores, some of the hyphae 

 being sterile. 



Nature of spores.— The spores of actinomycetes are spherical (0.8- 

 03l). in diameter), oval, or cylindrical (0.8-1 X 0.7[ji.). The shape and 

 size of the spores are characteristic of the species, with a certain degree 

 of gradation and variation. Actinomyces spores are reproductive bodies, 

 comparable to fungus spores, rather than resistant bodies like bacterial 

 spores. Actinomyces spores are destroyed by heat at 60° to 65°C. for 

 10 to 15 minutes. It has been (225) reported that the spores are 

 somewhat more resistant than the mycelium. 



When brought into a favorable medium, the spores swell and give 

 rise to one to four germ tubes. The different spores vary greatly in this 

 respect. Both the conidia and the oidiospores germinate in a manner 

 sirpilar to that of the corresponding spores of fungi. The germ tubes 

 may appear at one end or at both ends of the cylindrical oidiospore. 



