Satoshi Imura - Academia.edu (original) (raw)

Papers by Satoshi Imura

Research paper thumbnail of Microbiomic Analysis of Bacteria Associated with Rock Tripe Lichens in Continental and Maritime Antarctic Regions

Journal of Fungi

Increased research attention is being given to bacterial diversity associated with lichens. Rock ... more Increased research attention is being given to bacterial diversity associated with lichens. Rock tripe lichens (Umbilicariaceae) were collected from two distinct Antarctic biological regions, the continental region near the Japanese Antarctic station (Syowa Station) and the maritime Antarctic South Orkney Islands (Signy Island), in order to compare their bacterial floras and potential metabolism. Bulk DNA extracted from the lichen samples was used to amplify the 18S rRNA gene and the V3-V4 region of the 16S rRNA gene, whose amplicons were Sanger- and MiSeq-sequenced, respectively. The fungal and algal partners represented members of the ascomycete genus Umbilicaria and the green algal genus Trebouxia, based on 18S rRNA gene sequences. The V3-V4 sequences were grouped into operational taxonomic units (OTUs), which were assigned to eight bacterial phyla, Acidobacteriota, Actinomyceota, Armatimonadota, Bacteroidota, Cyanobacteria, Deinococcota, Pseudomonadota and the candidate phylum S...

Research paper thumbnail of Meteorological data from ice-free areas in Yukidori Zawa, Langhovde and Kizahashi Hama, Skarvsnes on Sôya Coast, East Antarctica during December 2014-December 2016

Research paper thumbnail of A new interstitial genus and species of Acrocirridae from Okinawa-jima Island, Japan

Zoosymposia, 2020

A new interstitial acrocirrid, Actaedrilus yanbarensis gen et. sp. nov., is described from Okinaw... more A new interstitial acrocirrid, Actaedrilus yanbarensis gen et. sp. nov., is described from Okinawa-jima Island, Japan. Individuals of the new genus and species were collected from the interstices of subtidal coarse sand (about 1 m depth). The new genus is comprised of the new species and A. polyonyx (Eliason, 1962) comb. nov. and it is characterized by the presence of two pairs of long branchiae, non-retractile head, minute body, and short club-shaped palps. We infer the phylogenetic position of A. yanbarensis gen. et sp. nov. within Acrocirridae using five gene markers (COI, 16S, 18S, 28S, Cyt B).

Research paper thumbnail of Complete Genome Sequence of Novel Psychrotolerant Legionella Strain TUM19329, Isolated from Antarctic Lake Sediment

Microbiology Resource Announcements, 2020

Here, we report the complete genome sequence characteristics of Legionella strain TUM19329, a can... more Here, we report the complete genome sequence characteristics of Legionella strain TUM19329, a candidate for a novel psychrotolerant species isolated from Antarctic lake sediment. The genome assembly contains a single 3,750,805-bp contig with a G+C content of 39.1% and is predicted to encode 3,538 proteins.

Research paper thumbnail of First records of Brada kudenovi Salazar-Vallejo, 2017 (Annelida, Flabelligeridae) from Japan

Check List, 2020

We reassess two specimens, part of the late Dr Minoru Imajima’s collections, from Japan of the fl... more We reassess two specimens, part of the late Dr Minoru Imajima’s collections, from Japan of the flabelligerid genus Brada Stimpson, 1853. We re-identify the specimens as B. kudenovi Salazar-Vallejo, 2017 and newly record this species from Japan, which represents the southernmost locality of the genus worldwide. The specimens were previously reported as B. inhabilis (Rathke, 1843), which has Molde, Norway as its type locality. However, the morphological features are identical to the original description of B. kudenovi in the following: the body is whitish in alcohol; there are one or two multiarticulate notochaetae per parapodium; the neuropodial lobes are low, not projecting; and the body papillae are short.

Research paper thumbnail of Species Identification of Pinus Pollen Found in Belukha Glacier, Russian Altai Mountains, Using a Whole-Genome Amplification Method

Forests, 2018

Pollen taxa in sediment samples can be identified based on morphology. However, closely related s... more Pollen taxa in sediment samples can be identified based on morphology. However, closely related species do not differ substantially in pollen morphology, and accurate identification is generally limited to genera or families. Because many pollen grains in glaciers contain protoplasm, genetic information obtained from pollen grains should enable the identification of plant taxa at the species level. In the present study, species identification of Pinus pollen grains was attempted using whole-genome amplification (WGA). We used pollen grains extracted from surface snow (depth, 1.8–1.9 m) from the Belukha glacier in the summer of 2003. WGA was performed using a single pollen grain. Some regions of the chloroplast genome were amplified by PCR, and the DNA products were sequenced to identify the pollen grain. Pinus includes approximately 111 recognized species in two subgenera, four sections, and 11 subsections. The tree species Pinus sibirica and P. sylvestris are currently found at the...

Research paper thumbnail of STRUCTURE OF MOSS COLONIES IN THE SYOWA STATION AREA, ANTARCTICA (15th Symposium on Polar Biology)

Proceedings of the Nipr Symposium on Polar Biology, 1994

Research paper thumbnail of Micro-relief distribution of major mosses in ice-free areas along the Soya Coast, the Syowa Station area, East Antarctica

Polar Bioscience, Feb 1, 2004

Micro-relief distribution of five major mosses, Pottia heimii, Ceratodon purpureus, Bryum pseudot... more Micro-relief distribution of five major mosses, Pottia heimii, Ceratodon purpureus, Bryum pseudotriquetrum, Grimmia lawiana and Bryum argenteum, in the ice-free areas along the Sôya Coast, continental part of East Antarctica have been compared. Those five mosses showed three di#erent types of micro-relief distribution, at three di#erent types of sites: mounds, slopes and hollows. Pottia heimii and Ceratodon purpureus prevailed on mound sites mixed with cyanobacteria. In dryer mound environments cyanobacteria was supposed to play an important role in nitrogen fixation. Bryum pseudotriquetrum and Grimmia lawiana dominated on hollow sites covered with sand. A more moisture rich condition of the hollow may promote their abundance associated with their high photosynthetic ability at moist sites. Bryum argenteum showed a rather unclear micro-relief distribution pattern. It appeared chiefly on mounds, but on hollows also. Rich nutrient input by sea birds into its habitats may allow various site selection under environments favorable to distribution.

Research paper thumbnail of On the structures of moss colony in the Yukidori Valley, Langhovde, East Antarctica

Polar Bioscience, Feb 1, 2004

The moss vegetation developing in the Yukidori Valley, Langhovde, East Antarctica, was investigat... more The moss vegetation developing in the Yukidori Valley, Langhovde, East Antarctica, was investigated as based on the samples in the vertical cross-section housed as the herbarium specimens to categorize the structure of the moss colony and to determine the specific composition. The vegetation consists of pure colonies of one species, and mixed colonies composed of two or rarely three moss species. Each colony was classified by species composition and degree of unevenness. The active zone, decomposed zone which were seen in the vertical cross-section, and epiphytic condition on the surface such as cyanobacteria and imperfect lichens, and rhizoidal layers in the inside of colony were determined and measured. Furthermore, the relationship between epiphytic condition and the thickness of the pure and mixed colonies was discussed taking account of ecological significances of these structural features.

Research paper thumbnail of Culture of rhizoidal tubers on an aquatic moss in the lakes near the Syowa Station area, Antarctica

Proceedings of the Nipr Symposium on Polar Biology, Mar 1, 1992

Research paper thumbnail of A spectroscopic study on the effect of ultra-violet solar radiation in Antarctica on the human skin fibroblast cells

Geoscience Frontiers, 2013

A study on the effect of the solar ultraviolet radiation on the human skin fibroblast cells revea... more A study on the effect of the solar ultraviolet radiation on the human skin fibroblast cells revealed that the production of matrix metalloproteinase-2 was inhibited by the radiation. A CO 2 incubator connected by optical fibers to a reflector telescope for collecting the solar light was built at Syowa station by the 49th Japanese Antarctica Research Expedition. The direction of the telescope was continuously controlled by a sun-tracker to follow the movement of the Sun automatically. The intensity of the collected light was monitored by a portable spectrophotometer housed inside. The human skin fibroblast cells were incubated in the CO 2 chamber to investigate the effect of the solar radiation at Syowa station and were compared with those reference experiments at a laboratory in Japan. The results showed cell damage by strong UV radiation. The production of matrix metalloproteinase-2 was prompted by the moderate UV-B, but was inhibited by the strong UV-B radiation, as studied under laboratory conditions in Japan. The effect of strong solar radiation at Syowa station involving the radiation of UV-B region was estimated to be of the same extent of the radiation caused by an artificial UV-B light with the intensity more than 50 mJ/cm 2 .

Research paper thumbnail of Reproductive phenology of subalpine moss, Polytrichurn ohioense Ren. et Card

The reproductive phenology of Polytrichum ohioense was investigated in a sub-alpine forest at the... more The reproductive phenology of Polytrichum ohioense was investigated in a sub-alpine forest at the foot of Mt. Tyausu, in the Yatsugatake Mountains, Central Honshu, Japan. Shoots were collected every 2 weeks from May to October from the study site. Developmental stages of gametangia and sporophytes formed in the current and previous year were registered. The temperature above the turf occasionally dropped below OC before June, while the temperature in the turf did not drop below OC. Juvenile antheridia formed about one month earlier than archegonia. Mature antheridia and archegonia are observed from late May to early August and from late June to mid-July, respectively. Fertilization seems to occur from late June to mid July. Longer persistence of mature antheridia is supposed to contribute to higher efficiency of fertilization to supply its sperm for a relatively long period. And delayed formation of archegonia in the warm season may contribute to the adaptation to the temperature decrease at the beginning of the growing season. Sporophytes were found first at the end of June, then gradually grew and reached the ECI stage by October. The sporophytes seemed to spend the period of snow cover in the ECI stage, and started to grow again in the next growing season in May. Spore dispersal was observed from mid-July to mid-August. Sporophytes took 13 months to mature including a 6 month resting period. The phenological parameters observed in the present study provide a way to adapt to the the short growing season in the sub-alpine zone in Central Honshu, Japan.

Research paper thumbnail of Environmental changes in Syowa Station area of Antarctica during the last ,-** years inferred from organic components in lake sediment cores

Polar Bioscience

Organic components in sediment cores from Namazu Ike (lake) (length .* cm) and O «-ike (lake) (le... more Organic components in sediment cores from Namazu Ike (lake) (length .* cm) and O «-ike (lake) (length-, cm) from Syowa Station area, Antarctica were studied to clarify their features in relation to paleoenvironmental changes, together with carbon-+. dating by Tandetron accelerator mass spectrometry. Namazu Ike sediment core was mainly composed of algal (mainly cyanobacteria) and aquatic moss debris, whereas O «-ike sediment core was comprised of coarse and fine sands with the influence of algal (mainly cyanobacteria) debris. The ages of core bottoms of Namazu Ike and O «-ike were estimated to be +//* and ,-* years before present (yBP), respectively. The sedimentation rates of Namazu Ike and O «-ike were calculated to be-* and /3 years/cm, respectively. Very high total organic carbon (TOC) contents (average ,../ῌ) of Namazu Ike revealed that the sediment core was mainly composed of organic matter. Dramatic increase of TOC/total nitrogen ratios at a depth of ,/ cm in Namazu Ike strongly suggests that aquatic moss increased from ++** yBP to the core top. Changes in n-alkanes, n-alkanoic and n-alkenoic acids, and sterol compositions in the O «-ike sediment core, suggest that microbial composition changed considerably, but their source organisms are not clear and further studies are required.

Research paper thumbnail of Archaeal and bacterial community structures in the anoxic sediment of Antarctic meromictic lake Nurume-Ike

Polar Science, 2010

Prokaryotic community structures in the anoxic sediment of the Antarctic meromictic Lake Nurume-I... more Prokaryotic community structures in the anoxic sediment of the Antarctic meromictic Lake Nurume-Ike were revealed by sequence analysis of 16S rRNA gene clones. The archaeal clones obtained (205 total) consisted of only three phylotypes, and were dominantly affiliated with uncultured euryarchaeotes. Specifically, 93% of the clones were identified as marine benthic group-D archaeal phylotype. In contrast to the limited archaeal diversity, 53 phylotypes were detected within 312 bacterial clones. Major bacterial phylotypes were affiliated with a-Proteobacteria (20% of clones), d-Proteobacteria (9%), Planctmycetales (7%), and Cyanobacteria (7%). A small numbers of clones belonging to g-Proteobacteria, Actinobacteria, Spirochaetes, Flavobacteria, and Verrucomicrobia were also found. A total of 53% of the bacterial clones, consisting of 13 phylotypes, could not be classified into any known group. These results indicated that the bacterial community of Lake Nurume-Ike sediment consisted of numerous phylogenetic groups and had a diversity comparable to the diversity of other Antarctic lakes communities previously reported. Interestingly, however, there were very few phylotypes shared between the communities of lakes Nurume-Ike and five other lakes located in the Vestfold Hills area. This is the first comprehensive study to analyze more than 500 16S rDNA clones for microbial community analysis of an Antarctic lake sediment sample, and the results significantly expand current views of bacterial diversity in Antarctic lakes.

Research paper thumbnail of Microflorae of aquatic moss pillars in a freshwater lake, East Antarctica, based on fatty acid and 16S rRNA gene analyses

Research paper thumbnail of Cultivation and Characterization of Microorganisms in Antarctic Lakes

OCEANS 2008 - MTS/IEEE Kobe Techno-Ocean, 2008

Microorganisms were isolated from Antarctica lakes and identified based on 16S rDNA sequence anal... more Microorganisms were isolated from Antarctica lakes and identified based on 16S rDNA sequence analysis. The lake samples were collected from Antarctic lakes in Skavrvsnes near Syowa Station area. When cultivation of lake water was performed at 4 ºC and 20 ºC in several selection media, most of microorganisms could not grow at 20 ºC, but they could efficiently grow at 4 ºC, indicating that low incubation temperature was more suitable for microorganisms in Antarctica lake. 16S rDNA of each isolate was sequenced. Homology search on GenBank showed that some clones were closely related to class of Flavobacteria, Bacilli, Actinobacteria, Alpha-proteobacteria, and Gamma-proteobacteria. A strain which grew at 20 ºC was identical to previously characterized bacterium (Gillisia limnaea) with 93% of 16S rDNA similarity, which suggested that this strain might be representative of novel genera.

Research paper thumbnail of コラーゲン人工皮膚を用いた紫外線カット素材の紫外線防御評価

FIBER, 2009

For preventing damages on the skin by UV-rays, various UV-cut materials have been developed. In t... more For preventing damages on the skin by UV-rays, various UV-cut materials have been developed. In the present study, the authors made a collagen sheet (hereafter "collagen artificial skin") to imitate the human skin on an experimental basis and, after having covered this sheet with a film added with various UV-protecting agents, subjected it artificially to UV-irradiation. Under such condition, the skin protective effect of each kind of UV-cut materials against UV rays was examined, and the various methods to evaluate damages on the sheet caused by UV rays were also reviewed. First, the UV-rays were applied to the collagen artificial skin that was not covered with the film, and the extracts were obtained from the sheet after irradiation. The analysis of the extracts by electrophoresis revealed that the bands of three molecular chains such as- ,-, and-chains of polypeptides were disappeared under UV-irradiation even only for 15 minutes (UV-Energy : 7.58×10 4 J/m 2 , at 310nm). When the irradiation time reached 25 hours (UV-Energy : 7.58×10 6 J/m 2 , at 310nm), hydrolysates from the collagen in the sheet started to appear, and when the irradiation time exceeded further 200 hours (UV-Energy : 6.06×10 7 J/m 2 , at 310nm), a considerable amount of hydrolysates was recognized. Also it was found that the longer the irradiation time of UV-rays, the higher the concentration of the terminal amino group in the extracts from the collagen was observed. Then, the UV-rays were irradiated to the collagen artificial skin added with various UV-scattering agents. As a result, addition of UV-scattering agents to the film of any of the materials reduced scission of the collagen molecular chains caused by UV-rays, resulting in reduction of the increase of the terminal amino group concentration. From the above results, it was suggested that the use of a collagen artificial skin was one of the effective measures as a method for examining the protective effect against UV-rays.

Research paper thumbnail of Abundance and diversity of functional genes involved in the degradation of aromatic hydrocarbons in Antarctic soils and sediments around Syowa Station

Environmental science and pollution research international, 2015

Hydrocarbon catabolic genes were investigated in soils and sediments in nine different locations ... more Hydrocarbon catabolic genes were investigated in soils and sediments in nine different locations around Syowa Station, Antarctica, using conventional PCR, real-time PCR, cloning, and sequencing analysis. Polycyclic aromatic hydrocarbon ring-hydroxylating dioxygenase (PAH-RHD)-coding genes from both Gram-positive and Gram-negative bacteria were observed. Clone libraries of Gram-positive RHD genes were related to (i) nidA3 of Mycobacterium sp. py146, (ii) pdoA of Terrabacter sp. HH4, (iii) nidA of Diaphorobacter sp. KOTLB, and (iv) pdoA2 of Mycobacterium sp. CH-2, with 95-99 % similarity. Clone libraries of Gram-negative RHD genes were related to the following: (i) naphthalene dioxygenase of Burkholderia glathei, (ii) phnAc of Burkholderia sartisoli, and (iii) RHD alpha subunit of uncultured bacterium, with 41-46 % similarity. Interestingly, the diversity of the Gram-positive RHD genes found around this area was higher than those of the Gram-negative RHD genes. Real-time PCR showed di...

Research paper thumbnail of Absence of a Medieval Climate Anomaly, Little Ice Age and twentieth century warming in Skarvsnes, Lützow Holm Bay, East Antarctica

Antarctic Science, 2014

Palaeoclimate changes, such as the Medieval Climate Anomaly and the Little Ice Age, are well-defi... more Palaeoclimate changes, such as the Medieval Climate Anomaly and the Little Ice Age, are well-defined in the Northern Hemisphere during the past 2000 years. In contrast, these anomalies appear to be either absent, or less well-defined, in high-latitude regions of the Southern Hemisphere. Here, we inferred environmental changes during the past two millennia from proxies in a sediment core from Mago Ike, an East Antarctic lake in Skarvsnes (Lützow Holm Bay). Variations in lake primary production were inferred from fossil pigments, sedimentological and geochemical proxies and combined with absolute diatom counts to infer past diatom productivity and community changes. Three distinct stratigraphic zones were recognized, resulting from a shift from marine to lacustrine conditions with a clear transition zone in between. The presence of open-water marine diatoms indicates a coastal zone seasonally free of sea ice between c. 2120–1500 cal yr bp. Subsequently, the lake became isolated from t...

Research paper thumbnail of Novel Biogenic Aggregation of Moss Gemmae on a Disappearing African Glacier

PLoS ONE, 2014

Tropical regions are not well represented in glacier biology, yet many tropical glaciers are unde... more Tropical regions are not well represented in glacier biology, yet many tropical glaciers are under threat of disappearance due to climate change. Here we report a novel biogenic aggregation at the terminus of a glacier in the Rwenzori Mountains, Uganda. The material was formed by uniseriate protonemal moss gemmae and protonema. Molecular analysis of five genetic markers determined the taxon as Ceratodon purpureus, a cosmopolitan species that is widespread in tropical to polar region. Given optimal growing temperatures of isolate is 20-30uC, the cold glacier surface might seem unsuitable for this species. However, the cluster of protonema growth reached approximately 10uC in daytime, suggesting that diurnal increase in temperature may contribute to the moss's ability to inhabit the glacier surface. The aggregation is also a habitat for microorganisms, and the disappearance of this glacier will lead to the loss of this unique ecosystem.

Research paper thumbnail of Microbiomic Analysis of Bacteria Associated with Rock Tripe Lichens in Continental and Maritime Antarctic Regions

Journal of Fungi

Increased research attention is being given to bacterial diversity associated with lichens. Rock ... more Increased research attention is being given to bacterial diversity associated with lichens. Rock tripe lichens (Umbilicariaceae) were collected from two distinct Antarctic biological regions, the continental region near the Japanese Antarctic station (Syowa Station) and the maritime Antarctic South Orkney Islands (Signy Island), in order to compare their bacterial floras and potential metabolism. Bulk DNA extracted from the lichen samples was used to amplify the 18S rRNA gene and the V3-V4 region of the 16S rRNA gene, whose amplicons were Sanger- and MiSeq-sequenced, respectively. The fungal and algal partners represented members of the ascomycete genus Umbilicaria and the green algal genus Trebouxia, based on 18S rRNA gene sequences. The V3-V4 sequences were grouped into operational taxonomic units (OTUs), which were assigned to eight bacterial phyla, Acidobacteriota, Actinomyceota, Armatimonadota, Bacteroidota, Cyanobacteria, Deinococcota, Pseudomonadota and the candidate phylum S...

Research paper thumbnail of Meteorological data from ice-free areas in Yukidori Zawa, Langhovde and Kizahashi Hama, Skarvsnes on Sôya Coast, East Antarctica during December 2014-December 2016

Research paper thumbnail of A new interstitial genus and species of Acrocirridae from Okinawa-jima Island, Japan

Zoosymposia, 2020

A new interstitial acrocirrid, Actaedrilus yanbarensis gen et. sp. nov., is described from Okinaw... more A new interstitial acrocirrid, Actaedrilus yanbarensis gen et. sp. nov., is described from Okinawa-jima Island, Japan. Individuals of the new genus and species were collected from the interstices of subtidal coarse sand (about 1 m depth). The new genus is comprised of the new species and A. polyonyx (Eliason, 1962) comb. nov. and it is characterized by the presence of two pairs of long branchiae, non-retractile head, minute body, and short club-shaped palps. We infer the phylogenetic position of A. yanbarensis gen. et sp. nov. within Acrocirridae using five gene markers (COI, 16S, 18S, 28S, Cyt B).

Research paper thumbnail of Complete Genome Sequence of Novel Psychrotolerant Legionella Strain TUM19329, Isolated from Antarctic Lake Sediment

Microbiology Resource Announcements, 2020

Here, we report the complete genome sequence characteristics of Legionella strain TUM19329, a can... more Here, we report the complete genome sequence characteristics of Legionella strain TUM19329, a candidate for a novel psychrotolerant species isolated from Antarctic lake sediment. The genome assembly contains a single 3,750,805-bp contig with a G+C content of 39.1% and is predicted to encode 3,538 proteins.

Research paper thumbnail of First records of Brada kudenovi Salazar-Vallejo, 2017 (Annelida, Flabelligeridae) from Japan

Check List, 2020

We reassess two specimens, part of the late Dr Minoru Imajima’s collections, from Japan of the fl... more We reassess two specimens, part of the late Dr Minoru Imajima’s collections, from Japan of the flabelligerid genus Brada Stimpson, 1853. We re-identify the specimens as B. kudenovi Salazar-Vallejo, 2017 and newly record this species from Japan, which represents the southernmost locality of the genus worldwide. The specimens were previously reported as B. inhabilis (Rathke, 1843), which has Molde, Norway as its type locality. However, the morphological features are identical to the original description of B. kudenovi in the following: the body is whitish in alcohol; there are one or two multiarticulate notochaetae per parapodium; the neuropodial lobes are low, not projecting; and the body papillae are short.

Research paper thumbnail of Species Identification of Pinus Pollen Found in Belukha Glacier, Russian Altai Mountains, Using a Whole-Genome Amplification Method

Forests, 2018

Pollen taxa in sediment samples can be identified based on morphology. However, closely related s... more Pollen taxa in sediment samples can be identified based on morphology. However, closely related species do not differ substantially in pollen morphology, and accurate identification is generally limited to genera or families. Because many pollen grains in glaciers contain protoplasm, genetic information obtained from pollen grains should enable the identification of plant taxa at the species level. In the present study, species identification of Pinus pollen grains was attempted using whole-genome amplification (WGA). We used pollen grains extracted from surface snow (depth, 1.8–1.9 m) from the Belukha glacier in the summer of 2003. WGA was performed using a single pollen grain. Some regions of the chloroplast genome were amplified by PCR, and the DNA products were sequenced to identify the pollen grain. Pinus includes approximately 111 recognized species in two subgenera, four sections, and 11 subsections. The tree species Pinus sibirica and P. sylvestris are currently found at the...

Research paper thumbnail of STRUCTURE OF MOSS COLONIES IN THE SYOWA STATION AREA, ANTARCTICA (15th Symposium on Polar Biology)

Proceedings of the Nipr Symposium on Polar Biology, 1994

Research paper thumbnail of Micro-relief distribution of major mosses in ice-free areas along the Soya Coast, the Syowa Station area, East Antarctica

Polar Bioscience, Feb 1, 2004

Micro-relief distribution of five major mosses, Pottia heimii, Ceratodon purpureus, Bryum pseudot... more Micro-relief distribution of five major mosses, Pottia heimii, Ceratodon purpureus, Bryum pseudotriquetrum, Grimmia lawiana and Bryum argenteum, in the ice-free areas along the Sôya Coast, continental part of East Antarctica have been compared. Those five mosses showed three di#erent types of micro-relief distribution, at three di#erent types of sites: mounds, slopes and hollows. Pottia heimii and Ceratodon purpureus prevailed on mound sites mixed with cyanobacteria. In dryer mound environments cyanobacteria was supposed to play an important role in nitrogen fixation. Bryum pseudotriquetrum and Grimmia lawiana dominated on hollow sites covered with sand. A more moisture rich condition of the hollow may promote their abundance associated with their high photosynthetic ability at moist sites. Bryum argenteum showed a rather unclear micro-relief distribution pattern. It appeared chiefly on mounds, but on hollows also. Rich nutrient input by sea birds into its habitats may allow various site selection under environments favorable to distribution.

Research paper thumbnail of On the structures of moss colony in the Yukidori Valley, Langhovde, East Antarctica

Polar Bioscience, Feb 1, 2004

The moss vegetation developing in the Yukidori Valley, Langhovde, East Antarctica, was investigat... more The moss vegetation developing in the Yukidori Valley, Langhovde, East Antarctica, was investigated as based on the samples in the vertical cross-section housed as the herbarium specimens to categorize the structure of the moss colony and to determine the specific composition. The vegetation consists of pure colonies of one species, and mixed colonies composed of two or rarely three moss species. Each colony was classified by species composition and degree of unevenness. The active zone, decomposed zone which were seen in the vertical cross-section, and epiphytic condition on the surface such as cyanobacteria and imperfect lichens, and rhizoidal layers in the inside of colony were determined and measured. Furthermore, the relationship between epiphytic condition and the thickness of the pure and mixed colonies was discussed taking account of ecological significances of these structural features.

Research paper thumbnail of Culture of rhizoidal tubers on an aquatic moss in the lakes near the Syowa Station area, Antarctica

Proceedings of the Nipr Symposium on Polar Biology, Mar 1, 1992

Research paper thumbnail of A spectroscopic study on the effect of ultra-violet solar radiation in Antarctica on the human skin fibroblast cells

Geoscience Frontiers, 2013

A study on the effect of the solar ultraviolet radiation on the human skin fibroblast cells revea... more A study on the effect of the solar ultraviolet radiation on the human skin fibroblast cells revealed that the production of matrix metalloproteinase-2 was inhibited by the radiation. A CO 2 incubator connected by optical fibers to a reflector telescope for collecting the solar light was built at Syowa station by the 49th Japanese Antarctica Research Expedition. The direction of the telescope was continuously controlled by a sun-tracker to follow the movement of the Sun automatically. The intensity of the collected light was monitored by a portable spectrophotometer housed inside. The human skin fibroblast cells were incubated in the CO 2 chamber to investigate the effect of the solar radiation at Syowa station and were compared with those reference experiments at a laboratory in Japan. The results showed cell damage by strong UV radiation. The production of matrix metalloproteinase-2 was prompted by the moderate UV-B, but was inhibited by the strong UV-B radiation, as studied under laboratory conditions in Japan. The effect of strong solar radiation at Syowa station involving the radiation of UV-B region was estimated to be of the same extent of the radiation caused by an artificial UV-B light with the intensity more than 50 mJ/cm 2 .

Research paper thumbnail of Reproductive phenology of subalpine moss, Polytrichurn ohioense Ren. et Card

The reproductive phenology of Polytrichum ohioense was investigated in a sub-alpine forest at the... more The reproductive phenology of Polytrichum ohioense was investigated in a sub-alpine forest at the foot of Mt. Tyausu, in the Yatsugatake Mountains, Central Honshu, Japan. Shoots were collected every 2 weeks from May to October from the study site. Developmental stages of gametangia and sporophytes formed in the current and previous year were registered. The temperature above the turf occasionally dropped below OC before June, while the temperature in the turf did not drop below OC. Juvenile antheridia formed about one month earlier than archegonia. Mature antheridia and archegonia are observed from late May to early August and from late June to mid-July, respectively. Fertilization seems to occur from late June to mid July. Longer persistence of mature antheridia is supposed to contribute to higher efficiency of fertilization to supply its sperm for a relatively long period. And delayed formation of archegonia in the warm season may contribute to the adaptation to the temperature decrease at the beginning of the growing season. Sporophytes were found first at the end of June, then gradually grew and reached the ECI stage by October. The sporophytes seemed to spend the period of snow cover in the ECI stage, and started to grow again in the next growing season in May. Spore dispersal was observed from mid-July to mid-August. Sporophytes took 13 months to mature including a 6 month resting period. The phenological parameters observed in the present study provide a way to adapt to the the short growing season in the sub-alpine zone in Central Honshu, Japan.

Research paper thumbnail of Environmental changes in Syowa Station area of Antarctica during the last ,-** years inferred from organic components in lake sediment cores

Polar Bioscience

Organic components in sediment cores from Namazu Ike (lake) (length .* cm) and O «-ike (lake) (le... more Organic components in sediment cores from Namazu Ike (lake) (length .* cm) and O «-ike (lake) (length-, cm) from Syowa Station area, Antarctica were studied to clarify their features in relation to paleoenvironmental changes, together with carbon-+. dating by Tandetron accelerator mass spectrometry. Namazu Ike sediment core was mainly composed of algal (mainly cyanobacteria) and aquatic moss debris, whereas O «-ike sediment core was comprised of coarse and fine sands with the influence of algal (mainly cyanobacteria) debris. The ages of core bottoms of Namazu Ike and O «-ike were estimated to be +//* and ,-* years before present (yBP), respectively. The sedimentation rates of Namazu Ike and O «-ike were calculated to be-* and /3 years/cm, respectively. Very high total organic carbon (TOC) contents (average ,../ῌ) of Namazu Ike revealed that the sediment core was mainly composed of organic matter. Dramatic increase of TOC/total nitrogen ratios at a depth of ,/ cm in Namazu Ike strongly suggests that aquatic moss increased from ++** yBP to the core top. Changes in n-alkanes, n-alkanoic and n-alkenoic acids, and sterol compositions in the O «-ike sediment core, suggest that microbial composition changed considerably, but their source organisms are not clear and further studies are required.

Research paper thumbnail of Archaeal and bacterial community structures in the anoxic sediment of Antarctic meromictic lake Nurume-Ike

Polar Science, 2010

Prokaryotic community structures in the anoxic sediment of the Antarctic meromictic Lake Nurume-I... more Prokaryotic community structures in the anoxic sediment of the Antarctic meromictic Lake Nurume-Ike were revealed by sequence analysis of 16S rRNA gene clones. The archaeal clones obtained (205 total) consisted of only three phylotypes, and were dominantly affiliated with uncultured euryarchaeotes. Specifically, 93% of the clones were identified as marine benthic group-D archaeal phylotype. In contrast to the limited archaeal diversity, 53 phylotypes were detected within 312 bacterial clones. Major bacterial phylotypes were affiliated with a-Proteobacteria (20% of clones), d-Proteobacteria (9%), Planctmycetales (7%), and Cyanobacteria (7%). A small numbers of clones belonging to g-Proteobacteria, Actinobacteria, Spirochaetes, Flavobacteria, and Verrucomicrobia were also found. A total of 53% of the bacterial clones, consisting of 13 phylotypes, could not be classified into any known group. These results indicated that the bacterial community of Lake Nurume-Ike sediment consisted of numerous phylogenetic groups and had a diversity comparable to the diversity of other Antarctic lakes communities previously reported. Interestingly, however, there were very few phylotypes shared between the communities of lakes Nurume-Ike and five other lakes located in the Vestfold Hills area. This is the first comprehensive study to analyze more than 500 16S rDNA clones for microbial community analysis of an Antarctic lake sediment sample, and the results significantly expand current views of bacterial diversity in Antarctic lakes.

Research paper thumbnail of Microflorae of aquatic moss pillars in a freshwater lake, East Antarctica, based on fatty acid and 16S rRNA gene analyses

Research paper thumbnail of Cultivation and Characterization of Microorganisms in Antarctic Lakes

OCEANS 2008 - MTS/IEEE Kobe Techno-Ocean, 2008

Microorganisms were isolated from Antarctica lakes and identified based on 16S rDNA sequence anal... more Microorganisms were isolated from Antarctica lakes and identified based on 16S rDNA sequence analysis. The lake samples were collected from Antarctic lakes in Skavrvsnes near Syowa Station area. When cultivation of lake water was performed at 4 ºC and 20 ºC in several selection media, most of microorganisms could not grow at 20 ºC, but they could efficiently grow at 4 ºC, indicating that low incubation temperature was more suitable for microorganisms in Antarctica lake. 16S rDNA of each isolate was sequenced. Homology search on GenBank showed that some clones were closely related to class of Flavobacteria, Bacilli, Actinobacteria, Alpha-proteobacteria, and Gamma-proteobacteria. A strain which grew at 20 ºC was identical to previously characterized bacterium (Gillisia limnaea) with 93% of 16S rDNA similarity, which suggested that this strain might be representative of novel genera.

Research paper thumbnail of コラーゲン人工皮膚を用いた紫外線カット素材の紫外線防御評価

FIBER, 2009

For preventing damages on the skin by UV-rays, various UV-cut materials have been developed. In t... more For preventing damages on the skin by UV-rays, various UV-cut materials have been developed. In the present study, the authors made a collagen sheet (hereafter "collagen artificial skin") to imitate the human skin on an experimental basis and, after having covered this sheet with a film added with various UV-protecting agents, subjected it artificially to UV-irradiation. Under such condition, the skin protective effect of each kind of UV-cut materials against UV rays was examined, and the various methods to evaluate damages on the sheet caused by UV rays were also reviewed. First, the UV-rays were applied to the collagen artificial skin that was not covered with the film, and the extracts were obtained from the sheet after irradiation. The analysis of the extracts by electrophoresis revealed that the bands of three molecular chains such as- ,-, and-chains of polypeptides were disappeared under UV-irradiation even only for 15 minutes (UV-Energy : 7.58×10 4 J/m 2 , at 310nm). When the irradiation time reached 25 hours (UV-Energy : 7.58×10 6 J/m 2 , at 310nm), hydrolysates from the collagen in the sheet started to appear, and when the irradiation time exceeded further 200 hours (UV-Energy : 6.06×10 7 J/m 2 , at 310nm), a considerable amount of hydrolysates was recognized. Also it was found that the longer the irradiation time of UV-rays, the higher the concentration of the terminal amino group in the extracts from the collagen was observed. Then, the UV-rays were irradiated to the collagen artificial skin added with various UV-scattering agents. As a result, addition of UV-scattering agents to the film of any of the materials reduced scission of the collagen molecular chains caused by UV-rays, resulting in reduction of the increase of the terminal amino group concentration. From the above results, it was suggested that the use of a collagen artificial skin was one of the effective measures as a method for examining the protective effect against UV-rays.

Research paper thumbnail of Abundance and diversity of functional genes involved in the degradation of aromatic hydrocarbons in Antarctic soils and sediments around Syowa Station

Environmental science and pollution research international, 2015

Hydrocarbon catabolic genes were investigated in soils and sediments in nine different locations ... more Hydrocarbon catabolic genes were investigated in soils and sediments in nine different locations around Syowa Station, Antarctica, using conventional PCR, real-time PCR, cloning, and sequencing analysis. Polycyclic aromatic hydrocarbon ring-hydroxylating dioxygenase (PAH-RHD)-coding genes from both Gram-positive and Gram-negative bacteria were observed. Clone libraries of Gram-positive RHD genes were related to (i) nidA3 of Mycobacterium sp. py146, (ii) pdoA of Terrabacter sp. HH4, (iii) nidA of Diaphorobacter sp. KOTLB, and (iv) pdoA2 of Mycobacterium sp. CH-2, with 95-99 % similarity. Clone libraries of Gram-negative RHD genes were related to the following: (i) naphthalene dioxygenase of Burkholderia glathei, (ii) phnAc of Burkholderia sartisoli, and (iii) RHD alpha subunit of uncultured bacterium, with 41-46 % similarity. Interestingly, the diversity of the Gram-positive RHD genes found around this area was higher than those of the Gram-negative RHD genes. Real-time PCR showed di...

Research paper thumbnail of Absence of a Medieval Climate Anomaly, Little Ice Age and twentieth century warming in Skarvsnes, Lützow Holm Bay, East Antarctica

Antarctic Science, 2014

Palaeoclimate changes, such as the Medieval Climate Anomaly and the Little Ice Age, are well-defi... more Palaeoclimate changes, such as the Medieval Climate Anomaly and the Little Ice Age, are well-defined in the Northern Hemisphere during the past 2000 years. In contrast, these anomalies appear to be either absent, or less well-defined, in high-latitude regions of the Southern Hemisphere. Here, we inferred environmental changes during the past two millennia from proxies in a sediment core from Mago Ike, an East Antarctic lake in Skarvsnes (Lützow Holm Bay). Variations in lake primary production were inferred from fossil pigments, sedimentological and geochemical proxies and combined with absolute diatom counts to infer past diatom productivity and community changes. Three distinct stratigraphic zones were recognized, resulting from a shift from marine to lacustrine conditions with a clear transition zone in between. The presence of open-water marine diatoms indicates a coastal zone seasonally free of sea ice between c. 2120–1500 cal yr bp. Subsequently, the lake became isolated from t...

Research paper thumbnail of Novel Biogenic Aggregation of Moss Gemmae on a Disappearing African Glacier

PLoS ONE, 2014

Tropical regions are not well represented in glacier biology, yet many tropical glaciers are unde... more Tropical regions are not well represented in glacier biology, yet many tropical glaciers are under threat of disappearance due to climate change. Here we report a novel biogenic aggregation at the terminus of a glacier in the Rwenzori Mountains, Uganda. The material was formed by uniseriate protonemal moss gemmae and protonema. Molecular analysis of five genetic markers determined the taxon as Ceratodon purpureus, a cosmopolitan species that is widespread in tropical to polar region. Given optimal growing temperatures of isolate is 20-30uC, the cold glacier surface might seem unsuitable for this species. However, the cluster of protonema growth reached approximately 10uC in daytime, suggesting that diurnal increase in temperature may contribute to the moss's ability to inhabit the glacier surface. The aggregation is also a habitat for microorganisms, and the disappearance of this glacier will lead to the loss of this unique ecosystem.