Comparison of methods for measuring viable E. coli cells during cultivation: Great differences in the early and late exponential growth phases

Four methods, namely enumeration of colony-forming units (CFU), aerobic respiration, MTT reduction capacity and succinate dehydrogenase activity were compared to determine the viability of E. coli cells at the early and late exponential growth phases. Our results revealed that great differences in cell viability existed between these methods and that the choice of method to determine cell viability must be made with caution.