Microplasma has the advantage of reducing the discharge voltage compared with other atmospheric plasmas. It is generated at atmospheric pressure at only around 1.0 kV since its discharge gap is on the order of micrometers. The experiment was performed with air and argon as the process gases, to confirm the influence of different radical species in the microplasma, on the bacteria cultures. The process gas flows through the parallel plate electrodes with holes which were covered with dielectric material and energized at about 1.0 kV. The active species generated by the dielectric-barrier discharge microplasma flows toward the exposed Escherichia coli on the agar media at a distance of 2 mm from the electrodes. The process is known as remote microplasma sterilization method. Microplasma generated by both air and Ar is effective for sterilization. Observation by the scanning-electron-microscope images shows that the E. coli had a shrunk shape after the microplasma treatment.