Abstract
Freshwater is essential to life in a closed habitation. An enormous amount of freshwater is used for drinking, daily use and hydroponics and recycled. In order to control the microbiological quality of the water used in a closed habitation system, it is important to rapidly obtain accurate information of the numbers and types of organisms. In this study, we applied the fluorescent vital staining (double staining with 6-carboxyfluorescein diacetate (CFDA) and 4',6-diamidino-2-phenyl indole (DAPI)) and microcolony method to freshwater used in the Closed Ecology Experiment Facilities (CEEF) and determined the abundance and physiological activity of the bacteria in this closed habitation system. Bacterial population dynamics were analyzed by denaturing gradient gel electrophoresis (DGGE) with the PCR-amplified 16S rRNA gene of bacteria in water used in closed habitation system. Bacterial numbers in the purified water in the tank, tap water and shower of this system were 103 to 105 cells/mL during the experimental period. Many of the cells had esterase- and/or growth activities and the proportion of bacteria with the growth activities gradually increased. In the water used for hydroponics, the bacterial number was 105 to 106 cells/mL. The bacterial community structure was steady in purified water in the tank, but the dominant bacteria in the hydroponic solution in the tank were significantly changed. These techniques would provide early warning of an impending problem and might be applicable to rapid and accurate microbial monitoring of a closed habitation.
