Activation of Soil Microflora by Fungus Spores in Relation to Soil Fungistasis

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Abstract
Bacterial numbers in natural soil supplemented with living fungus spores or cell-free aqueous washings of spores, then incubated for 8 hr. or more, were several-fold higher than those in non-supplemented soil. Rates of oxygen uptake in natural soil supplemented with washed or unwashed fungus spores, cell-free aqueous washings of spores, killed spores or diluted nutrients, were several-fold higher than those in non-supplemented soil. Increased respiration occurred rapidly on addition of these supplements to soil. A single brief water washing of urediospores of Puccinia rubigo-vera or of conidia of Neurospora sp. extracted about 10% of the spore dry weight. Washed bacteria or Streptomyces spp., when incubated with fungus spores in absence of added nutrients, inhibited fungus spore germination, whereas sterile filtrates of bacteria were not inhibitory. The results indicate that fungus spores, by virtue of nutrients in their exudates, stimulate rapid activity of microbes in soil, and that the enhanced microbial activity causes inhibition of fungal spore germination.