| Budget Amount *help |
¥1,900,000 (Direct Cost: ¥1,900,000)
Fiscal Year 1996: ¥700,000 (Direct Cost: ¥700,000)
Fiscal Year 1995: ¥1,200,000 (Direct Cost: ¥1,200,000)
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| Research Abstract |
The bottom sediments, sampled at several sites in Northern and Southrn basin of Lake Biwa, were separated according to their depth (0-1,2-3,5-6,9-10cm) from its surface. The microbial flora in the sediments were investigated by counting colonies formed on agar plates of a nutrient broth and a diluted nutrient broth agar medium. The activity of the sediments to decompose organic substances (minerilization activity), supposed to relate a remediation activity of the sediments, were investigated by measuring the ^<14>CO_2 production when ^<14>C-labeled glucose was added to the sediments.
Followings were observed concerning the microbial flora, 1) the number of oligotrophic microbes were greater than that of eutrophic ones, 2) In the deeper sediments less aerobes were found (especially in summer), 3) in the Northern basin slow-growing microbes were major, contrary to this 4) in the Southern basin fast-growing microbes were major.
The activity to decompose organic substance (glucose) were similar between the sediments in the Northern basin and that in the Southern basin, despite the difference in the number of microbes. Many more facultative anaerobes in the Northern basin compared with the Southern basin seemed to produce much more CO_2.
In the layr of sediments from 0 to 10mm deep, almost all the microbes were aerobes. The number of microbes in the layr from 0 to 1mm changed greatly in different seasons.
In a related research, the number of microbes resistant to various antibiotics were investigated. The ratio of the resistant microbes were greater in the deeper sediments. Some progress was made in the relevant studies such as the development of a system to measure the microbial attachment force, the analysis of the polymer structure at microbial cells and its relation with the cell attachment.
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