Dynamic analysis of coliform group in the sea and estuary of Ariake-kai bay

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Bacteria of coliform group concluding Escherichia coli are not usually found in natural environment such as sea and river. However, it is known that such bacteria can be detected in the sea and river polluted by sewage of towns and cities. In present study, we attempt to clarify the dynamic analysis of coliform group in the sea and estuary of Ariake-kai bay. In Shirakawa River, that flows in Ariake-kai through Kumamoto city, we observed a large amount of coliform group. And, we could detect also the bacteria in the whole sea area of Ariake-kai bay, though the amount of those was a little. From the experimental observation that cells of Escherichia coli could survive in seawater for at least one month, it is considered that a constant amount of coliform group may exist always in the sea and coastal zone of Ariake-kai.However, we found the interesting fact that coliform group could not detect in several tidelands of Ariake-kai. From these results, some factor(s) in the soil of tideland are considered to affect the survival of coliform group. Therefore, we carried out to identify the factor(s) in the soil of that. Although we could not identify perfectly the factor(s), it seems that the factor(s) are certain microorganism(s) which are lethal over the temperature of 60 ℃ and their size of cells is l.2〜5.0μm. Further study is needed on the identification and property of the factor(s) of tideland. It should be very interesting to clarify the role of tideland affecting the preservation of natural environment contaminated by external bacteria such as Escherichia coli. Studies along this line are in progress in our laboratory.