54 INTERRELATIONSHIPS AMONG MICROORGANISMS 



(361), whether the organisms thereby affected are able to overcome 

 their effect, and whether they are destroyed by other members of the 

 soil or water microbiological population (947, 951). 



Different organisms possess different degrees as well as different 

 mechanisms of antagonism. Often one organism may completely check 

 the growth of another j later, growth may be resumed, although it will 

 not be quite normal. Antagonism stimulates spore-production and 

 brings about deformed growth of the mycelium in fungi or the forma- 

 tion of gigantic cells in bacteria. Distortions were found to be produced 

 in Alternar'ia (231) and in HelTninthosforium (695) by a bacterial 

 antagonist. The morphological effects produced by the antagonists com- 

 prise changes in form, size, and structure of hyphae, direction of growth, 

 and complete cessation of growth and abbreviation of hyphal segments. 



In surveying the phenomena of antagonism among microorganisms, 

 Porter (695) reached the conclusion that, among bacteria, the spore- 

 formers are strong inhibitors. Actinomycetes also exhibit strong inhibi- 

 tory action against most filamentous fungi. Phycomycetes usually 

 neither cause inhibition nor are inhibited j the Basidiomycetes contain 

 very few organisms possessing antagonistic properties. Ascomycetes 

 and Fungi Imperfecti vary greatly in their ability to produce antibac- 

 terial substances; some yeasts are strong inhibitors. Certain algae, no- 

 tably species of Chlorella, produce a substance (chlorellin) that inhibits 

 the growth of various gram-positive and gram-negative bacteria (701). 



