.M(tIn'll()l.()(;^■, ('VT()l,()(;^•. and i.ii'I': ('^■('I-!';s 



83 



The sjiiral-shnpod sponilatinj; liypliac aic 

 characteristic in their sti-uclurc and lcii<ith, 

 the iiiiinlx'f (»!' turns Ixmiiu; I to •_'(), usually 

 .") to 10, the cui\atui"('s IxMiiji; clockwise 

 tilext lorse) oi' countorcl()ck\vis(> (siiiisli-orse). 

 Kutzuei- (>\ainino(l 'AS'2 strains of Slnpli)- 

 miices. Of these, 20o fornied no spirals, 1 .").'; 

 produced sinistrorse and 2() dexti'orse spirals, 

 similar to the prexious ohserxations of 

 Dreclisler anil Stapp (l!)")^). 



The sporulating liyphae consist of sterile 

 axial filaments bearing sporulating branches 

 in a i-aceinose or caj>itat(> arrangement. The 

 primary branches may function directly as 

 sporogenous hyphae or may produce second- 

 ary sporulating branches. Sporogenesis is 

 usually conhned to the terminal elements, 

 and the hyphal portions below the points of 

 attachment of such branches remain sterile. 



The specializetl, sporogenous hyphae can 

 l)e distinguished from the sterile hj'^phae of 

 the aerial mycelium at an early stage of 

 development. The diameter of the sterile 

 mycelium, which arises through the elonga- 

 tion of the growing hyphal filaments, shows 

 little increase. In the beginning, the sporoge- 

 nous hyphae are usually thinner than the 

 axial hyphae from which they are derived. 

 After the final linear extension has been 

 attained, the sporogenous hyphae are in 

 most cases appreciably thicker. 



The pigmentation of the aerial mycelium 

 is characteristic of the species and depends 

 on the composition of the medium and the 

 length of incubation period. The pigments 

 range from white or gray to yellow, orange, 

 red, rose, lavender, blue and green. 



The sporophores in the aerial mj'celium of 

 streptomycetes are highly characteristic. 

 Pridham et al. (1958) ba.sed a system of 

 classification of the genus Streptomyccs upon 

 this property, as shown in Chapter 20, \o\- 

 ume II. The sporophores are either straight 

 or spiral-forming. As shown prexiously, the 

 spirals curve not long before the spores are 

 produced; the sporulating hyphae may be 



cur\('d throughout or onl>' at the end. The 

 number of turns wirics in accordance with 

 the length ol the spiral, as shown al)o\('. Not 

 all t he aerial hyphae gi\'e ri.se to spores, some 

 of the hyi)liae remaining sterile. 



.Vnothcr interesting phenomenon obserxcd 

 in the aeiial mycelium of some species of 

 Slrcploinucc.s is verticil formation, the sporu- 

 lating hyphae lieing arranged in groups of 

 .') to 10, eiiuidistant from one another. 

 Waksman (11)19) first reported this for S. 

 reticuli and N. reticuloruber , the second 

 producing the verticils on the side branches 

 of the aerial mycelium. Kriss (1937), Kras- 

 .silnikov (1941), Xakazawa (1954-1955), and 

 others attached so much importance to this 

 that the S. reticuli group was considered as 

 of considerable taxonomic interest. Some of 

 them produce straight and others spiral- 

 shaped sporulating branches. The compo- 

 sition of the medium is of great significance, 

 synthetic media being most favorable to 

 their formation. Shinobu differentiated be- 

 tween the Nitella type of verticil, in which 

 the sporulating branches are straight {S. 

 reticuli type of Waksman), and the Anitella 

 type, in which the sporulating branches are 

 spiral shaped. The "tuft" type of Waksman 

 is considered as a form of the Nitella type 

 in which the distance between nodes is very 

 short. More detailed studies of this have 

 been made by ]*ridham et al. and others. 



Prolonged cultivation of actinomycetes 

 may lead to an alteration in the tj'pe of aerial 

 mycelium or to complete loss of formation 

 of aerial mycelium. ^Morphological changes 

 in\'ohing similar structures in other micro- 

 organisms were found to be influenced by 

 diffusible substances from streptomyces 

 (Grossbard). Dondero and Scotti have shown 

 that old laboratory strains of streptomyces, 

 which had been carried on artificial media 

 for 4 to 40 years, could be induced syner- 

 gistically to form aerial hyphae again; \'ar- 

 ious strains excreted diffusilile substances 



