細胞生物学的研究手法を用いた自然環境の調査方法の探索

Abstract

This research aims to develop new teaching materials for Natural Sciences education customized for liberal arts students. To raise students' awareness of global environmental issues and encourage practical measures, it is necessary to understand the key factors that causing these issues and how they affect nature. Plants and microbes have great abilities to absorb industrial pollutants and degrade biomass for recycle, playing a central role in natural purification. However, the increasing consumption of natural resources and loss of biodiversity have severely disrupted the balance, resulting in excessive accumulation of harmful elements and substances that cannot be easily visualized or recognized in our environment. Therefore, this preliminary study attempts to design molecular and cell biological methods to help students detect and analyze pollutants and understand the importance of biodiversity, and furthermore, to provide scientific evidence and reasonable solutions for environmental issues. The investigations focused on the soil and water organisms at the Musashi University campus and air pollution control in Tokyo Metropolitan area. In the soil samples collected at four different locations, a large number of microbes were detected using streak plate method, in which soil bacteria are isolated and cultured in agar plates to form visible colonies (in microbiology, a colony is defined as a group of bacteria originating from a single mother cell). Four sampling sites represent different ecological environments, where tall evergreen tree (A), grass (B) and shrubs at downstream (C) and upstream (D) of an artificial river (Susugi River) are nourished. Accordingly, the soil components and texture are also different as observed. Humic substances are high molecular weight organic compounds in soil, which are formed during natural decomposition and transformation of biomass residues by the action of microorganisms. Humic acids, one of the three categories of humic substances, contribute to soil fertility and help trapping heavy metal ions from waters. In this report, acid-base extraction method was employed to isolate humic acids from soil samples, and the adsorption capacity of humic acids was investigated by observing color changes of copper sulfate solution and bentonite (a natural clay) sediments. To investigate the abundance of biomass in soil and water, protein quantitation was performed using an advanced Bradford method. This analysis requires the operation of micropipettes to deal with small volumes of reagents under 1 mL, and a high-throughput detection was achieved by using microplate reader, which can measure 96 samples at a time in 1 minute. Among four soil samples, the highest protein content was found in site D; while in the water samples, the downstream of Susugi River (C) showed a higher protein concentration than that of the upstream (D). However, in the colony counting result, water D sample contained much more bacteria than water C sample, suggesting that water flow might affect microorganism survival and organic matter accumulation. In the air pollution investigation, 80 sites in Tokyo Metropolitan area were monitored and the concentration (ppm) of nitrogen dioxide (NO2), an air pollutant, was measured by a colorimetric assay using Salzman's reagent. Although all the monitoring locations have passed the Air Quality Standards (under 0.020 ppm), the NO2 concentration was found to be closely related to the traffic volume by comparing main streets with residential areas. It was also suggested that plants (leaves) may have a NO2 absorption effect. In the future, repeated experiments are required to confirm statistical significance; and moreover, investigation on different types of plants and soil microorganisms may provide more useful evidence to address environmental problems.