Phylogenetic analysis of Rhodococcus erythropolis based on the variation of ribosomal proteins as observed by matrix-assisted laser desorption ionization-mass spectrometry without using genome information

Rhodococcus erythropolis strains characterized as antibiotic producers can be classified into three groups according to their antibiotic spectrum and growth compatibility. Due to their high genotypic similarity, the taxonomic relationship of these strains has not been elucidated. In this study, ribosomal protein profiling using matrix-assisted laser desorption ionization-mass spectrometry (MALDI-MS) was employed to classify twenty-one strains of R. erythropolis (15 antibiotic producers and 6 non-antibiotic producers). In the first step in this method, a total of 30 intense peaks observed for purified ribosomal subunit proteins of the type strain (R. erythropolis JCM 3201^T) were selected as the reference peaks. The mass spectra observed for the cell lysates of each sample strain were then checked as to whether peaks were observed at the same masses of the reference peaks. The results of peak matching were processed by cluster analysis, generating a dendrogram. Four major clusters of the R. erythropolis strains corresponded to three antibiotic groups and the non-antibiotic group. Furthermore, the topology of the dendrogram was highly comparable with the phylogenetic tree based on DNA gyrase subunit B gene (gyrB) sequencing. These results indicate that our proposed ribosomal protein profiling method using MALDI-MS is a potentially reliable and sufficiently high-throughput technique for the taxonomic analysis of closely related bacterial strains without using DNA sequence information.     

資源環境の保全をめざした二次副産材を導入するコンクリ一ト材料の発展的利用に関する研究

日本では,21世紀半ばに人工の固体物質の代表である解体コンクリート塊の排出量がピークを迎えると同時に,最終処分が困難になる状況が想定されていることから,コンクリート材料の完全資源型の利活用要求はより一層高まるといえる.本研究は,副産微粉,再生骨材などの二次副産材を積極的に混和し,同一産地*種類型の調合条件のもとで,コンクリートの物性改善,資源有効利活用を目的としたコンクリートを製造し,その基礎的物性の評価と環境影響評価を行い,環境保全に資するコンクリート材料の発展的利用のあり方を検討した.     

Structural and magnetic properties of Lix(MnyFe1−y)PO4 electrode materials for Li-ion batteries

A series of LiMn_yFe_1−yPO₄ samples have been prepared in the whole range 0 ≤ y ≤ 1. Chemical delithiation could be achieved to obtain Mn_yFe_1−yPO₄ in the range 0 ≤ y ≤ 0.8, keeping the same crystal phase (olivine structure, space group Pnma). The composition y = 0.8 is the limit where the delithiated phase is still crystallized, but abruptly suffers strains at the molecular scale evidenced by both optical spectroscopy and X-ray diffraction. The analysis of the magnetic properties shows that in all the samples the concentration of impurities is negligible. The concentration of polarons, either holes associated to Li vacancies in LiMn_yFe_1−yPO₄ or electrons associated to the existence of Li left in the matrix of Mn_yFe_1−yPO₄, is found to be small (≤1%) in all the samples. For y ≤ 0.6, all the Mn³⁺ ions Mn_yFe_1−yPO₄ are in the high-spin state (S = 2). At larger manganese concentration, however, the Mn³⁺ ions in excess of the critical concentration y_c = 0.6 undergo a transition to the low-spin state (S = 1). As a consequence, and in contrast with prior works, we find that Mn_0.8Fe_0.2PO₄ has magnetic interactions that are much smaller, and no antiferromagnetic ordering in this compound is detected, at least above 20 K. Antiferromagnetic ordering that had been reported so far for Mn_yFe_1−yPO₄ at large y-composition might come from incomplete delithiation. The spin-transition of Mn³⁺ in concentration (y–y_c) to the low-spin state is at the origin of the strain fields at the molecular scale that increase with y for y > 0.6, and ultimately prevents the full delithiation for y > 0.8. This result sheds light on the reason for the degradation of cathode properties in Mn-rich compounds of the heterosite–purpurite series, while the electrochemical properties are good in the range y ≤ 0.6 but only at slow rates, due to the very small hopping mobility of the small polaron.     

Cellular and transcriptional responses of yeast to the cleavage of cytosolic tRNAs induced by colicin D

Colicin D is a plasmid‐encoded antibacterial protein that specifically cleaves the anticodon loops of four Escherichia coli tRNA^Arg species. Here, we report that the catalytic domain of colicin D, which is expressed in Saccharomyces cerevisiae, impairs cell growth by cleaving specific tRNAs. DNA microarray analysis revealed that mating‐related genes were upregulated, while genes involved in a range of metabolic processes were downregulated, thereby impairing cell growth. The pheromone‐signalling pathway was activated only in α cells by tRNA cleavage, which was not observed in ‘a’ cells or diploid cells. On the basis of these results and on the recent identification of two killer toxins that cleave specific tRNAs, the relationship between tRNA depletion and the resultant cellular response is discussed. Copyright © 2009 John Wiley & Sons, Ltd.     

Isolation of Solid Solution Phases in Size‐Controlled LixFePO4 at Room Temperature

State‐of‐the‐art LiFePO₄ technology has now opened the door for lithium ion batteries to take their place in large‐scale applications such as plug‐in hybrid vehicles. A high level of safety, significant cost reduction, and huge power generation are on the verge of being guaranteed for the most advanced energy storage system. The room‐temperature phase diagram is essential to understand the facile electrode reaction of Li_xFePO₄ (0 < x < 1), but it has not been fully understood. Here, intermediate solid solution phases close to x = 0 and x = 1 have been isolated at room temperature. Size‐dependent modification of the phase diagram, as well as the systematic variation of lattice parameters inside the solid‐solution compositional domain closely related to the electrochemical redox potential, are demonstrated. These experimental results reveal that the excess capacity that has been observed above and below the two‐phase equilibrium potential is largely due to the bulk solid solution, and thus support the size‐dependent miscibility gap model.     

Coherent Phase Diagram for Spinodal Decomposition in the Tetragonal Titanium Dioxide—Tin Oxide System

A microscopic calculation was carried out for spinodal decomposition in the tetragonal TiO₂—SnO₂ system by taking into account the contribution of the elastic free energy. Necessary elastic constants for the solid solutions and the elastic free energy of modulated structure were calculated in terms of interatomic potentials. A coherent phase diagram was obtained unambiguously from the calculated elastic free energy by using the interaction parameter determined by the experimental binodal line. The results were compared with the calculation based on the regular-solution model.     

Direct lattice imageing in single crystals of isotatic polystyrene

Lattice lines with 1.1 nm and 0.55 nm spacings were resolved in isotactic polystyrene (i-PS) single crystals using a conventional transmission electron microscope, equipped for low dose imageing. It is suggested that these crystals may be used as a model for the direct imageing of structural defects in polymer crystals.