The Bacillus subtilis exhibited strong resistance to the effect of plasma ( Fig. 2 A). However, obvious damages to the bacterium occurred when the plasma treatment time was long. The external wall of (gram-positive) Bacillus subtilis , was deformed when treatment extended to 120 s ( Fig. 3 C-2). As shown in Fig. 3 C-1, dense protoplasts are surrounded by a less dense spore cortex and a thick and multilayered spore coat. During the course of 120 s treatment the cortex became less dense and larger in size, and the endospore coats became more diffuse and partially degraded ( Fig. 3 C-2)