Strain of Strain of Colony Colony Cell type Effect Cell type Effect Capsule No capsule 静 ● ● Smooth(S) Live S strain Rough(R) Live R strain (a) (b) Effect e888。 Live R strain Effect Heat-killed Heat-killed S strain S strain Live S and R strains (c) (d) isolated from dead mouse Figure 2.2 Griffith's transformation experiments.(a)Virulent strain S S.pneumoniae kill their host;(b)avirulent strain R bacteria cannot infect successfully,so the mouse survives;(c)strain S bacteria that are heat-killed can no longer infect;(d)a mixture of strain R and heat-killed strain S bacteria kills the mouse.The killed virulent(S)bacteria have transformed the avirulent(R)bacteria to virulent(S). 转化：将无毒的R型菌在加热杀死的$型菌的作用下，转 化为有毒的$菌，称为转化。转化：将无毒的R型菌在加热杀死的S型菌的作用下，转 化为有毒的S菌，称为转化