興味対象の発見を支援するためのビデオカメラおよびビデオフレームアルバムの活用

ビデオカメラおよびビデオフレームアルバムの授業への活用を検討した。すなわち、学生にビデオカメラを持たせて、大学構内を自由に散策させ、その際気がついたこと、興味をもったことなどをビデオカメラで記録させた。さらに著者らがその映像記録をフレームアルバム化し、後日授業時間内で学生に返却して、見せるといった一連の授業を試みることにより、今回の試みが学生の新たな発想や興味対象の発見へのきっかけ作りになりうるかどうか検討した。ビデオカメラによる野外活動の行動様式への影響を支持する学生が多く、その理由として「ビデオを手にすると注意深くなる」「自分の印象深いものを人にわかるように撮った」といった感想と関連していると考えられる。また、自分の興味対象の発見に対してフレームアルバムを分析することは、比較的効果的であると評価され、「ビデオフレームアルバムはビデオを視聴するよりも全体の流れがわかってよい」といった感想も見られた。また、教授者にとっても映像記録を画像要素ごとに分類し、類似した画像のコマ数の多いものに注目することにより、各学生の興味対象を容易に比較分析することができた。今回の試みは、学生の野外観察時の行動様式や新たな興味対象の発見などに何らかの影響をおよぼしたものと考えられる。さらに、教授者が学生の興味対象を容易に比較分析できるため、学生との議論材料にも活用できるものと思われる。This study examined the effectiveness of a video camera and video-frame-albums to help students discover objects of particular interest to them. Biology students video-recorded things that interested them while they were walking outdoors. Video-frame-albums provided by an Automatic Printing System for Time-Sampled Video Pictures were efficiently used to analyze and compare students\u27 interests. The students concluded that the video-frame-albums were useful for discovering objects that interested them. They also concluded that carrying the video camera influenced their style of activity in the outdoors. These results suggest that trials in this study are effective to help students discover objects that interest them

Active Transport and Accumulation of Iodide by Newly Isolated Marine Bacteria

Iodide (I(−))-accumulating bacteria were isolated from marine sediment by an autoradiographic method with radioactive (125)I(−). When they were grown in a liquid medium containing 0.1 μM iodide, 79 to 89% of the iodide was removed from the medium, and a corresponding amount of iodide was detected in the cells. Phylogenetic analysis based on 16S rRNA gene sequences indicated that iodide-accumulating bacteria were closely related to Flexibacter aggregans NBRC15975 and Arenibacter troitsensis, members of the family Flavobacteriaceae. When one of the strains, strain C-21, was cultured with 0.1 μM iodide, the maximum iodide content and the maximum concentration factor for iodide were 220 ± 3.6 (mean ± standard deviation) pmol of iodide per mg of dry cells and 5.5 × 10(3), respectively. In the presence of much higher concentrations of iodide (1 μM to 1 mM), increased iodide content but decreased concentration factor for iodide were observed. An iodide transport assay was carried out to monitor the uptake and accumulation of iodide in washed cell suspensions of iodide-accumulating bacteria. The uptake of iodide was observed only in the presence of glucose and showed substrate saturation kinetics, with an apparent affinity constant for transport and a maximum velocity of 0.073 μM and 0.55 pmol min(−1) mg of dry cells(−1), respectively. The other dominant species of iodine in terrestrial and marine environments, iodate (IO(3)(−)), was not transported

Hydrogen Peroxide-Dependent Uptake of Iodine by Marine Flavobacteriaceae Bacterium Strain C-21▿

The cells of the marine bacterium strain C-21, which is phylogenetically closely related to Arenibacter troitsensis, accumulate iodine in the presence of glucose and iodide (I−). In this study, the detailed mechanism of iodine uptake by C-21 was determined using a radioactive iodide tracer, 125I−. In addition to glucose, oxygen and calcium ions were also required for the uptake of iodine. The uptake was not inhibited or was only partially inhibited by various metabolic inhibitors, whereas reducing agents and catalase strongly inhibited the uptake. When exogenous glucose oxidase was added to the cell suspension, enhanced uptake of iodine was observed. The uptake occurred even in the absence of glucose and oxygen if hydrogen peroxide was added to the cell suspension. Significant activity of glucose oxidase was found in the crude extracts of C-21, and it was located mainly in the membrane fraction. These findings indicate that hydrogen peroxide produced by glucose oxidase plays a key role in the uptake of iodine. Furthermore, enzymatic oxidation of iodide strongly stimulated iodine uptake in the absence of glucose. Based on these results, the mechanism was considered to consist of oxidation of iodide to hypoiodous acid by hydrogen peroxide, followed by passive translocation of this uncharged iodine species across the cell membrane. Interestingly, such a mechanism of iodine uptake is similar to that observed in iodine-accumulating marine algae

Microbial participation in iodine volatilization from soils.

The roles of microorganisms in iodine volatilization from soils were studied. Soils were incubated with iodide ion (I-), and volatile organic iodine species were determined with a gas chromatograph. Iodine was emitted mainly as methyl iodide (CH3I), and CH3I emission was sometimes enhanced by the addition of glucose. Soils were then incubated with a radioactive iodine tracer (125I), and radioiodine emitted from soils was determined. The emission of iodine was enhanced in the presence ofyeast extract, but was inhibited by autoclaving of soils. Theaddition of streptomycin and tetracycline, antibiotics which inhibit bacterial growth, strongly inhibited iodine emission, while a fungal inhibitor cycloheximide caused little effect. Forty bacterial strains were randomly isolated from soils, and their capacities for volatilizing iodine were determined. Among these, 14 strains volatilized significant amounts of iodine when they were cultivated with iodide ion. Phylogenetic analysis based on 16S ribosomal DNA sequences showed that these bacteria are widely distributed through the bacterial domain. Our results suggest that iodine in soils is methylated and volatilized as CH3I by the action of soil bacteria, and that iodine-volatilizing bacteria are ubiquitous in soil environments. The pathway of iodine volatilization by soil bacteria should be important for understanding the biogeochemical cycling of iodine as well as for the assessment of long-lived radioactive iodine (129I) in the environment