Temperature-dependent genetics of thermotolerance between yeast species

Many traits of industrial and basic biological interest arose long ago, and manifest now as fixed differences between a focal species and its reproductively isolated relatives. In these systems, extant individuals can hold clues to the mechanisms by which phenotypes evolved in their ancestors. We harnessed yeast thermotolerance as a test case for such molecular-genetic inferences. In viability experiments, we showed that extant Saccharomyces cerevisiae survived at temperatures where cultures of its sister species S. paradoxus died out. Then, focusing on loci that contribute to this difference, we found that the genetic mechanisms of high-temperature growth changed with temperature. We also uncovered a robust signature of positive selection at thermotolerance loci in S. cerevisiae population sequences. We interpret these results in light of a model of gradual acquisition of thermotolerance in the S. cerevisiae lineage along a temperature cline. We propose that in an ancestral S. cerevisiae population, alleles conferring defects at a given temperature would have been resolved by adaptive mutations, expanding the range and setting the stage for further temperature advances. Together, our results and interpretation underscore the power of genetic approaches to explore how an ancient trait came to be.

Effect of reactive gas condition on nonpolar AlN film growth on MnS/Si (100) by reactive DC sputtering

The effects of reactive gas flow conditions on nonpolar AlN film growth on MnS/Si (100) substrates using reactive DC magnetron sputtering were investigated. During AlN deposition at a substrate temperature of 750 °C, the MnS surface can be unintentionally nitrided, resulting in a decrease in the crystallinity of the AlN. Low temperature growth of the AlN layer at 300 °C prevents this nitridation and results in the crystallization of nonpolar AlN. A N2 flow equal to 30% of the Ar sputtering gas flow was found to improve the crystallinity of the nonpolar AlN and to reduce nitrogen defects, which play an important role in interfacial reactions. Nitrogen defects promote the formation of alloys such as AlMn and MnSi that degrade the interface and can significantly decompose the MnS. A higher proportion of N2 improves the nonpolar AlN crystallinity, reduces the concentration of defects and suppresses reactions at the AlN/MnS interface.

Controlled Growth of Indium Selenides by High-Pressure and High-Temperature Method

The controlled growth of indium selenides has attracted considerable research interests in condensed matter physics and materials science yet remains a challenge due to the complexity of the indium–selenium phase diagram. Here, we demonstrate the successful growth of indium selenides in a controllable manner using the high-pressure and high-temperature growth technique. The γ-InSe and α-In2Se3 crystals with completely different stoichiometries and stacking manner of atomic layers have been controlled grown by subtle tuning growth temperature, duration time, and growth pressure. The as-grown γ-InSe crystal features a semiconducting property with a prominent photoluminescence peak of ∼1.23 eV, while the α-In2Se3 crystal is ferroelectric. Our findings could lead to a surge of interest in the development of the controlled growth of high-quality van der Waal crystals using the high-pressure and high-temperature growth technique and will open perspectives for further investigation of fascinating properties and potential practical application of van der Waal crystals.

The C50 carotenoid bacterioruberin regulates membrane fluidity in pink-pigmented Arthrobacter species

Carotenoids have several crucial biological functions and are part of the cold adaptation mechanism of some bacteria. Some pink-pigmented Arthrobacter species produce the rare C50 carotenoid bacterioruberin, whose function in these bacteria is unclear and is found mainly in halophilic archaea. Strains Arthrobacter agilis DSM 20550T and Arthrobacter bussei DSM 109896T show an increased bacterioruberin content if growth temperature is reduced from 30 down to 10 °C. In vivo anisotropy measurements with trimethylammonium-diphenylhexatriene showed increased membrane fluidity and a broadening phase transition with increased bacterioruberin content in the membrane at low-temperature growth. Suppression of bacterioruberin synthesis at 10 °C using sodium chloride confirmed the function of bacterioruberin in modulating membrane fluidity. Increased bacterioruberin content also correlated with increased cell resistance to freeze–thaw stress. These findings confirmed the adaptive function of bacterioruberin for growth at low temperatures for pink-pigmented Arthrobacter species.

Plasma excited molecular beam epitaxy－proposal and achievements through R&D of compound semiconductor materials and devices－

This paper reviews 35 years of brief history on plasma-excited molecular beam epitaxy, focusing on special values added to conventional Molecular Beam Epitaxy (MBE) through usage of plasma-excited molecular beams. These include low temperature surface cleaning, low temperature growth, selected area re-growth and impurity doping. These technologies are extremely important to realize nano-scale low-dimensional device structures. InN and In-rich InGaN are also highlighted as unique material systems, which plasma-excited MBE process is inevitable to grow. Future prospect of this technology will also be included from the device application viewpoints.

Study of Ga2O3 deposition by MOCVD

Growth of Ga2O3 by metalorganic chemical vapour deposition in horizontal flow reactor from trimethylgallium (TMG) and oxygen is studied in a wide temperature range. The growth rate is directly proportional to TMG flow, weakly affected by O2 flow and non-monotonically depends on temperature. Growth rate over 3 μm/h is demonstrated, indicating that TMG can be used for growth of β-Ga2O3 thick layers for device applications.