Culture conditions of R2A media for the enumeration of bacteria in purified water
2006
Kakinuma, S.(Tanabe Seiyaku Co. Ltd., Osaka (Japan)) | Nawata, M. | Furusu, T. | Tachikawa, M. | Takahashi, E. | Yaku, K. | Osawa, T.
Bacteria present in purified water were enumerated by plate counts on R2A media and SCDA media, and identified. After 14 days of incubation, the number of colony forming units on R2A media was I to 4 times higher than on SCDA media. The isolated strains on R2A media were more diverse compared with those on SCDA media, and belonged almost entirely to the a Proteobacteria group. Therefore, it was more useful to use R2A media than SCDA media for the detection of the various kinds of heterotrophic bacteria in oligotrophic samples such as purified water. Bradyrhizobium sp. constituted a major part of the total number of strains isolated from purified water on R2A media. While many bacterial counts were obtained after incubation at 20 to 25 deg C on SCDA media, incubation at 30 to 35 deg C was adequate for plate counts on R2A media. However, bacteria present in water differed at each sampling point. Therefore, it is important to determine the culture conditions in advance. It is desirable to fix incubation periods at 7 days or more than 14 days according to the purpose of the microbial monitoring such as daily or periodic examinations.
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