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Mechanism of Lysis of Fungal Mycelia in Soil. Wen- hsiung Ko, Department of Botany and Plant Pathology, Michigan State University, East Lansing 48823, Present address of senior author: Department of Plant Pathology, University of Hawaii, Hawaii Agricultural Experiment Station, Hilo 96720; John L. Lockwood, Department of Botany and Plant Pathology, Michigan State University, East Lansing 48823. Phytopathology 60:148-154. Accepted for publication 25 August 1969. DOI: 10.1094/Phyto-60-148.

The role of autolysis in the lysis of fungal mycelia in natural soil was investigated. Beta- d-glucosidase and chitinase activity in living mycelia of Helminthosporium victoriae, Glomerella cingulata, and Fusarium solani increased rapidly during incubation on membrane filters placed on soil or sterile sand leached slowly with running water. Enzyme activation stopped when mycelium was transferred to a nutrient solution, but resumed when mycelium was returned to soil or leached sand. Activity of lytic enzymes in mycelia of the three fungi, or of the same fungus at different ages, during incubation on soil, was directly correlated with susceptibility to lysis. Several streptomycetes that caused only slight lysis of dead mycelia of the three fungi completely lysed living mycelia in buffer solutions. No antibiotic activity was detected in such cultures, nor in concentrated aqueous or organic solvent extracts of soil amended with 0.1% (dry wt basis) of mycelium of H. victoriae or G. cingulata. These data support the autolysis hypothesis for lysis of fungal mycelia in soil, and indicate that autolysis is induced by nutrient deprivation without involvement of antibiotics.