@misc{oai:tokyo-metro-u.repo.nii.ac.jp:00007025,
 author = {イデイ, アイリ and 出井, 愛理 and Idei, Airi},
 month = {Mar},
 note = {Microbial metabolism in iron-rich hot springs can provide insights into the role of both ancient and contemporary microbes related to iron oxidation. The oxidation of Fe(II) in some ancient periods, resulting in iron deposition, can partially be understood from the reaction with oxygen produced by cyanobacteria or oxygenic phototrophs. However, Fe(II) together with oxygen is toxic to many organisms, and cyanobacteria are no exception. A previous study showed that cyanobacteria responded negatively to anoxic and Fe(II) rich conditions. In this study, cyanobacteria obtained from iron-rich environments were tested to determine whether they were tolerant to iron-rich conditions. Two types of enrichment culture were obtained from microbial mats in Jinata hot springs in Shikine island, one of Izu islands. The marine hot springs had neutral pH and included 250 μM Fe(II). One area contained unicellular cyanobacteria (JNT 01) and phylogenetic analysis indicated that the bacterium is related to Cyanobacterium aponium (99 % identity). Cyanobacteria from the springs were cultured in the absence of Fe(II), aerobically. Then, the cyanobacteria cultured were grown in air-tight bottles under anoxic and Fe(II) containing conditions, at the beginning, in order to reveal the effect of Fe(II) on growth. The growth of one microcosm, containing a morphotype referred to here as JNT 01, was different from Synechococcus PCC 7002, as a control. JNT 01 in 600 μM initial Fe(II) grew as fast as in 0 μM Fe(II). The growth of Synechococcus PCC 7002 in 600 μM Fe(II) was about half of the growth in 0 μM Fe(II). During the growth of cells, the Fe(II) concentration diminished in several hours in both cultures. To reveal the difference in the growth of JNT 01 and Synechococcus PCC 7002 with Fe(II) in early growth phase, the growth conditions were changed. Synechococcus PCC 7002 sometimes grew in 200 μM better than in 0 μM. It seems to be the effect of Fe on the metabolism. Therefore, the timing of the addition of ferric citrate – a growth nutrient – was changed from before autoclaving to after autoclaving. Under the changed conditions, the growth of JNT 01 and Synechococcus PCC 7002 was similar. These experiments seemed to suggest that Synechococcus PCC 7002, but not JNT 01, was sensitive to an effect of the form of Fe as a nutrient for growth, and that the timing of autoclaving affected this. Since Fe(II) decreased in less than 24 hours in these experiments, it was difficult to make conclusions about the effects of Fe(II). To investigate these effects on growing cells, the initial growth of cells was examined. Less than 24 hours after the start of growth, Fe(II) was decreasing but still present. During this period, the growth of JNT 01 is significantly different from the growth of PCC 7002. In the later time when Fe(II) decreased, the difference became less significant. These results together suggested that the enriched unicellular cyanobacteria inhabiting in the Fe(II)-rich hot springs were tolerant to the ferrous iron rich conditions. It is possible that they have been adapted to iron-rich environments which are similar to that expected for Precambrian environments. This study provides insights into ancient iron transformations and mechanisms of Fe(II) toxicity in both modern and ancient ocean cyanobacteria., 首都大学東京, 2018-03-25, 修士（理学）},
 title = {Tolerance of Fe(II) Toxicity by Cyanobacteria Inhabiting an Iron-rich Hot Spring},
 year = {2018}
}