276 



THE ACTINOMYCETES, Vol. I 



for plant growth has not been fully eluci- 

 dated. 



Formation of small tubers on the roots of 

 the oleander has been demonstrated by Ro- 

 berg (1934). The organism is similar to A. 

 alni and was described as A. elaeagni. 



All three of these actinomycetes definitely 

 belong to the genus Nocardia. Only one of 

 them is included in the classification, namely, 

 A'', alni. 



A further study of these associations has 

 been made by von Plotho (1941). It was sug- 

 gested (Lieske) that the role of actinomy- 

 cetes consists in enabling the plant to fix 

 atmospheric nitrogen. 



Actinomycetes and Plant Development 



Lutman suggested that the occurrence of 

 actinomycetes in the outer layers of roots 

 and tubers of the potato plant corroborates 

 his theory that these organisms play an im- 

 portant role in plant growth. The stems 

 above ground are also infected; but the tips 

 of young roots and stems contain only a few 

 strands between the cells. These facts sug- 

 gested that the infection is systemic and he- 

 reditary. Young potato plants grown from 

 disinfected seed and in disinfected soil are 

 found to contain numerous actinomycete fil- 

 aments. 



According to Lutman, potato scab lesions 

 are associated with strands of actinomycetes 

 extending from the abnormal cells of the 

 cork camljium to the interior of the tuber. 

 Similar strands have been found in clean 

 tubers grown on land never known to pro- 

 duce scabby tubers. The strands found under 

 the scabs seem to be unusually large and 

 numerous, especially those about fi\^e to ten 

 cells below the pathological tissue. 



The cell walls of .lerusalcm artichoke tu- 

 bers and the enlarged roots of beets, carrots, 

 parsnips, and turnips contain gram-i)ositiv(! 

 filaments which seem to he of the same sort 

 as those occui-i'ing in the potato plant. The 

 suggestion was made that sincc^ actinomy- 



cetes are abundant in the roots of plants, 

 they may take part in the synthesis of alka- 

 loids and proteins. Since large numbers of 

 soil actinomycetes are pectin-dissolving, the 

 different varieties found in the various host 

 plants may be only modifications of one large 

 species. The walls of higher plants were be- 

 lieved to be living, through the presence and 

 action of strands of actinomycetes. The ef- 

 fects of actinomycete filaments surrounding 

 every cell suggested the theory that the ma- 

 terials they withdraw from the cells and the 

 products which they excrete and which must 

 be absorbed by the cells change the charac- 

 teristics of the cells. 



Richards outlined in detail the method of 

 staining the potato scab organism. The or- 

 ganism can be selectively impregnated with 

 carbol-auramin and when exposed to ultra- 

 violet radiation, it fluoresces bright yellow. 

 The hyphae are stained bright yellow. This 

 permits ready localization and study of the 

 micropathology of the tissue with a simple 

 fluorescence microscope. The staining tech- 

 nic is done at room temperature. No counter- 

 stain is used. The results obtained tended to 

 confirm Lutman's conclusion that the fila- 

 ments are intercellular and grow within the 

 middle lamellae. After complete remo\'al of 

 the paraffin, the sections are strained 4 min- 

 utes in carbon-aiu'amin (distilled water 97 

 ml, liquefied phenol 3 ml, certified auramin 

 0.1 gm), washed, destained in a 0.5 per cent 

 solution of XaCl in 70 per cent alcohol with 

 0.5 ml of HCl (cone.) per 100 ml, washed, 

 and mounted in glycerol. 



Voros et al. reported that streptomycin 

 exerts a protectiA-e effect upon the potato 

 plant, rendering it resistant to Phijthophtora, 

 via the polyphenol-polyphenolase system of 

 the host plant. The fact that polyphenolases 

 are copper enzjniies, their acti^•ity depend- 

 ing upon the copper supply of the plant, and 

 the fa(^t that copper and streptomycin were 

 found to exert a synergistic effect may help 

 to explain the aboN'e effect of streptomycin. 



