Most organic solvents (OSs) are toxic and inhibit growth of microorganisms even at low concentrations. Therefore, they are used to sterilize microbial cultures and to maintain solutions in a sterile condition. However, the physiological basis of such phenomenon is poorly understood. Although there are some microorganisms that can utilize a number of OSs as their sole carbon and energy sources, OSs must be provided as a vapor or at a very low concentration to avoid growth inhibition.