Recently, spreading of infectious diseases caused by antibiotic-resistant bacteria became a serious public health issue in the world. To combat antibiotic-resistant bacteria, it is very important to develop new antibiotics continuously. However, inost of the pathogenic bacteria easily gain resistance in a very short teriu (within few months) against newly developed antibiotics. Thus, there is an urgent need for the development of no vel antimicrobial agents, which act through a different mechanism from conventional antibiotics.