|Budget Amount *help
¥1,400,000 (Direct Cost : ¥1,400,000)
Fiscal Year 1999 : ¥500,000 (Direct Cost : ¥500,000)
Fiscal Year 1998 : ¥900,000 (Direct Cost : ¥900,000)
The bacteria-lysing substances released by the myxamoebae of a true slime mold, Didymium sp. Strain H-1 were studied. A drop of secretion from the myxamoebae was deposited on an agar plate containing a dense suspension of bacteria, Klebsiella pneumoniae. After appropriate incubation, a zone of lysis of bacteria, or a plaque, was formed at the point where the secretion had been deposited. The plaque ordinally consisted of two portions, a central transparent circle and a peripheral translucent ring. The myxamoebae secreted the bacteria-lysing substance and superoxide explosively during the initial stages of culture under aerobic conditions. This 'initial burst' was not observed under anaerobic conditions. The plaque made by the secretion from the 'initial burst' was large and transparent all over the circle. We consider, based on the results of gel filtration experiments, that the myxamoebae release two kinds of bacteria-lysing substance ; one with high molecular weight and the other with low molecular weight. We also consider that the high molecular substance only makes translucent plaque, but it can form a transparent zone if the low molecular substance cooperates. Whole-transparent plaque may be formed by the secretion from the 'initial burst' with the help of a low molecular substance synthesized to excess under oxidative conditions. In this microenvironment, as soon as the myxamoebae meet bacteria, they may release these substances explosively to obtain the best conditions to voraciously endocytose bacteria in order to ensure their own survival. This phenomenon may be termed the 'initial burst'.