抄録
Growth characteristics of flock forming Microcystis (K-3A, K-3, K-5) isolated from Lake Kasumigaura were studied under the various physical and chemical conditions. Moreover, effects of associated bacteria on the growth of Microcystis were investigated. K-3A was a bacteria free strain, while K-3 and K-5 were bacteria associated strains. The maximum specific growth rate (μmax) of these strains were observed at 30° to 35°C and the μmax value was 1.5 day-1. The light intensity for the maximum cell growth of all strains were between 1, 000 to 3, 000 lux, while the μmax of K-3 and K-5 was observed at 5, 000 and K-3A was at 3, 000 lux. The light intensity of μmax was higher than that of the maximum cell growth. The nitrogen, phosphorus and iron concentrations for μmax of all strains were 0.3 mg/l, 0.005 mg/l and 0.005 mg/l, respectively. It was concluded that physical and chemical environment conditions of Lake Kasumigaura in summer season were suited for the well growth of Microcystis. The μmax and the maximum cell growth of K-3A were significantly lower than those of K-3. It was considered that the association with bacteria was of great advantage to the growth of Microcystis.
