A POSSIBLE FUNCTION OF ACTINOMYCETES 



IN SOID 



H. JOEL CONN 

 Agricultural Experiment Station, Geneva, New York 



It is not generally agreed whether Actinomycetes are to be 

 classed with bacteria or with molds. They are thought to be- 

 long with the Hyphomycetes by some mycologists; but those 

 that occur in the soil have generally been considered in con- 

 nection with the bacterial flora rather than with the soil fungi. 

 The reason why they have been studied by soil bacteriologists 

 may be partly because Actinomycetes can be handled by much 

 the same methods as the lower bacteria; and partly because both 

 of these groups seem to be much more numerous than molds 

 proper in normal soil. 



The abundance of Actinomycetes in soil has been recognized 

 for some time. In 1903 Hiltner and Stormer (1903) showed 

 that of the colonies developing on gelatin plates from normal 

 soil, 5 per cent were ordinarily liquefiers, 70 per cent non- 

 liquefiers, and 20 per cent Streptothrix forms (a name often, al- 

 though incorrectly, applied to this group). Probably every- 

 one who has plated soil in gelatin, provided he has incubated 

 his plates long enough for the slow-growing organisms to ap- 

 pear, will recognize these figures as typical of ordmary soil. 



Perhaps the most interesting recent work on soil Actinomycetes 

 is that of Krainsky (1914). It contains a valuable classification 

 of these organisms and shows that the reason why few species 

 have been distinctly recognized in the past is because the Actino- 

 mycetes require special media in order to bring out their specific 

 characteristics. His further contention, however, that these 

 special media are necessary in ord6r to show the abundance of 



1 Presented at Seventeenth Annual Meeting of the Society of American Bac- 

 teriologists, Urbana, Illinois, December 29, 1915. 



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