沿岸海域における窒素固定ラン藻の生態・ゲノム学的研究

京都大学0048新制・課程博士博士(農学)甲第19778号農博第2174号新制||農||1041(附属図書館)学位論文||H28||N4994(農学部図書室)32814京都大学大学院農学研究科応用生物科学専攻(主査)教授 左子 芳彦, 教授 澤山 茂樹, 准教授 吉田 天士学位規則第4条第1項該当Doctor of Agricultural ScienceKyoto UniversityDFA

The first assessment of cyanobacterial and diazotrophic diversities in the Japan Sea

The diversity of cyanobacteria and diazotrophs in the Japan Sea was investigated by analyzing sequences of cyanobacterial 16S rRNA genes and nitrogen fixation genes (nifH) from seawater sampled at depths ranging from the surface to 100 m at two stations. Of the 107 cyanobacterial 16S rRNA gene sequences obtained, 97 and three sequences were assigned to Synechococcus sub-cluster 5.1 and Prochlorococcus HL (II), respectively. Unlike other oceanic regions, at our two sampling stations the composition ratio of the sequences assignable to Synechococcus sub-cluster 5.3 was relatively high (8 %). No sequences of diazotrophic cyanobacteria were found in the cyanobacterial 16S rRNA genes. In the nifH clone library (36 sequences), ten sequences were identified as a UCYN-A group of diazotrophic cyanobacteria; the other 26 sequences (72 %) were assigned to proteobacteria. These results suggest that heterotrophic bacteria, including UCYN-A, dominate the diazotrophic community in the Japan Sea. Our study reveals the dominance of Synechococcus in cyanobacterial community and (photo)heterotrophic diazotrophs in the diazotrophic community in the Japan Sea, suggesting its unique characteristics

Reducing energy consumption of heat pumps by introducing a thermal energy storage system

We proposed a short-term thermal energy storage system by applying Phase Change Materials (PCMs) in air ducts connected to an indoor air conditioning unit within a ceiling space. PCM tubes were arranged in a staggered layout in the air duct and cooled by chilled air from the air conditioning unit during “charging” mode, whereas the PCM tubes released cold energy to the room space without operation of the compressor during “discharging” mode. The charging mode allowed for an increase in the partial load ratio of the heat pump to prevent low-efficiency operation at <20% load, which can increase seasonal energy efficiency. We constructed an energy simulation program, where the heat exchange coefficient between the PCM tubes and air was varied with airflow rate and the temperature difference between the PCM and air, in accordance with results from CFD analysis. Switching between the charging and discharging modes was based on the outlet temperature (Tout) and 30% of the rated capacity of the indoor unit (Lr). The heat balance between the charging and discharging modes was improved by this change to the system control. A higher load factor and higher COP resulted in a 7.6% reduction in energy consumption

Diurnal infection patterns and impact of Microcystis cyanophages in a Japanese pond.

Viruses play important roles in regulating the abundance, clonal diversity, and composition of their host populations. To assess their impact on the host populations, it is essential to understand the dynamics of virus infections in the natural environment. Cyanophages often carry host-like genes, including photosynthesis genes, which maintain host photosynthesis. This implies a diurnal pattern of cyanophage infection depending on photosynthesis. Here we investigated the infection pattern of Microcystis cyanophage by following the abundances of the Ma-LMM01-type phage tail sheath gene g91 and its transcript in a natural population. The relative g91 mRNA abundance within host cells showed a peak during the daylight hours and was lowest around midnight. The phage g91 DNA copy numbers in host cell fractions, which are predicted to indicate phage replication, increased in the afternoon, followed by an increase in the free-phage fractions. In all fractions, at least 1 of 71 g91 genotypes was observed (in tested host cell, free-phage, and RNA fractions), indicating that the replication cycle of the cyanophage (i.e., injection, transcription, replication, and release of progeny phages) was occurring. Thus, Microcystis cyanophage infection occurs in a diel cycle, which may depend on the light cycle. Additionally, our data show that the abundance of mature cyanophage produced within host cells was 1 to 2 orders of magnitude greater than that of released phages, suggesting that phage production may be higher than previously reported

Cytoskeletal Regulation by AUTS2 in Neuronal Migration and Neuritogenesis

Mutations in the Autism susceptibility candidate 2 gene (AUTS2), whose protein is believed to act in neuronal cell nuclei, have been associated with multiple psychiatric illnesses, including autism spectrum disorders, intellectual disability, and schizophrenia. Here we show that cytoplasmic AUTS2 is involved in the regulation of the cytoskeleton and neural development. Immunohistochemistry and fractionation studies show that AUTS2 localizes not only in nuclei, but also in the cytoplasm, including in the growth cones in the developing brain. AUTS2 activates Rac1 to induce lamellipodia but downregulates Cdc42 to suppress filopodia. Our loss-of-function and rescue experiments show that a cytoplasmic AUTS2-Rac1 pathway is involved in cortical neuronal migration and neuritogenesis in the developing brain. These findings suggest that cytoplasmic AUTS2 acts as a regulator of Rho family GTPases to contribute to brain development and give insight into the pathology of human psychiatric disorders with AUTS2 mutations

Coefficient of Friction in Diamond-Like Carbon Films

The pin-on-plate and the pin-on-disk friction test were carried out to clarify the mechanism of low friction coefficient of diamond like carbon (DLC) films. As the test piece, six kinds of commercially available DLC coated specimens were prepared. The hydrogen content of DLC was determined by elastic recoil detection analysis (ERDA) method using 2 MeV of He ion beam from the tandem accelerator. Pin-on-plate type friction test was carried out with the combination of DLC coated pin and high-speed tool steel plate. As a result of the friction test, it became clear that in the case of these combinations, all DLC show a low coefficient of friction of 0.08 - 0.09 in initial term, and it rises with time. In the case of DLC with a low hydrogen content, debris of heat-affected DLC was not observed in and around the wear truck of plate. These tendency were different from the conventional experiment that coated DLC to a plate. As a general tendency in this experiment, harder DLC film maintained lower coefficient of friction. From this result, it was estimated that DLC with low abrasion maintain high contact pressure and develop a low coefficient of friction

Empagliflozin in Patients with Chronic Kidney Disease

Background The effects of empagliflozin in patients with chronic kidney disease who are at risk for disease progression are not well understood. The EMPA-KIDNEY trial was designed to assess the effects of treatment with empagliflozin in a broad range of such patients. Methods We enrolled patients with chronic kidney disease who had an estimated glomerular filtration rate (eGFR) of at least 20 but less than 45 ml per minute per 1.73 m(2) of body-surface area, or who had an eGFR of at least 45 but less than 90 ml per minute per 1.73 m(2) with a urinary albumin-to-creatinine ratio (with albumin measured in milligrams and creatinine measured in grams) of at least 200. Patients were randomly assigned to receive empagliflozin (10 mg once daily) or matching placebo. The primary outcome was a composite of progression of kidney disease (defined as end-stage kidney disease, a sustained decrease in eGFR to &lt; 10 ml per minute per 1.73 m(2), a sustained decrease in eGFR of &amp; GE;40% from baseline, or death from renal causes) or death from cardiovascular causes. Results A total of 6609 patients underwent randomization. During a median of 2.0 years of follow-up, progression of kidney disease or death from cardiovascular causes occurred in 432 of 3304 patients (13.1%) in the empagliflozin group and in 558 of 3305 patients (16.9%) in the placebo group (hazard ratio, 0.72; 95% confidence interval [CI], 0.64 to 0.82; P &lt; 0.001). Results were consistent among patients with or without diabetes and across subgroups defined according to eGFR ranges. The rate of hospitalization from any cause was lower in the empagliflozin group than in the placebo group (hazard ratio, 0.86; 95% CI, 0.78 to 0.95; P=0.003), but there were no significant between-group differences with respect to the composite outcome of hospitalization for heart failure or death from cardiovascular causes (which occurred in 4.0% in the empagliflozin group and 4.6% in the placebo group) or death from any cause (in 4.5% and 5.1%, respectively). The rates of serious adverse events were similar in the two groups. Conclusions Among a wide range of patients with chronic kidney disease who were at risk for disease progression, empagliflozin therapy led to a lower risk of progression of kidney disease or death from cardiovascular causes than placebo