??????????????? Methylosinus trichosporium OB3b??? ????????? ?????? ????????????????????? poly-?? -hydroxybutyric acid(PHB)??? ??????

An obligatory methanotroph Methylosinus trichosporium OB3b was cultivated for the production of poly-?? -hydroxybutyric acid(PHB) in shake-flask using liquefied natural gas(LNG) as the sole source of carbon and energy. The maximal specific growth rate decreased by 40% using LNG compared with that obtained with pure methane. This is attributed to the inhibition by ethane and propane presents in the LNG as impurities. For the production of PHB, two-stage culture separating the production stage from the growth stage was carried out. PHB accumulation was observed after switching nutrient-sufficient to nutrient-limited condition of non-carboneous component (NO3-, PO43-, K+, Na+, Fe2+, or Mg2+). The limitation of K+ or Mg2+ resulted in relatively high PHB content, but the highest content was obtained by nitrate limitation. The optimal pH and temperature for PHB accumulation was 7.0 and 30???C . Under the optimal condition the maximal PHB content was about 45% after 4-day cultivation

??????????????? Methylosinus trichosporium OB3b??? ?????? ????????? ?????? : I. ????????? ??????

The effect of culture medium copper availability on the specific growth rate(?? ) and carbon conversion efficiency (CCE) was sutided for an obligatory methanotroph Methylosinus trichosporium OB3b under various combinations of carbon and nitrogen sources. Methane or methanol was used as a carbon source, and nitrate or ammonium was used as a nitrogen source. Medium copper availability determined the intracellular location or kind of methane monooxygenase (MMO), cell-membrane (particulate or pMMO) when copper was present and cytoplasm (soluble or sMMO) when copper was deficient. When methane was used as a carbon source, copper-containing medium exhibited higher ?? and CCE than copper-free medium regardless of the kind of nitrogen source. When methanol was used as a carbon source, however, the effect of copper disappeared. Ammonium gave the higher ?? and CCE than nitrate for both methane and methanol. Those observation suggest that there exist an important difference in energy utilization efficiency for methane assimilation between sMMO and pMMO

Structure and function of actin filaments in mature guard cells

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2021 update on ATP-binding cassette (ABC) transporters: how they meet the needs of plants

11Nsciescopu

Oscillatory ROP GTPase Activation Leads the Oscillatory Polarized Growth of Pollen Tubes

Oscillation regulates a wide variety of processes ranging from chemotaxis in Dictyostelium through segmentation in vertebrate development to circadian rhythms. Most studies on the molecular mechanisms underlying oscillation have focused on processes requiring a rhythmic change in gene expression, which usually exhibit a periodicity of >10 min. Mechanisms that control oscillation with shorter periods (<10 min), presumably independent of gene expression changes, are poorly understood. Oscillatory pollen tube tip growth provides an excellent model to investigate such mechanisms. It is well established that ROP1, a Rho-like GTPase from plants, plays an essential role in polarized tip growth in pollen tubes. In this article, we demonstrate that tip-localized ROP1 GTPase activity oscillates in the same frequency with growth oscillation, and leads growth both spatially and temporally. Tip growth requires the coordinate action of two ROP1 downstream pathways that promote the accumulation of tip-localized Ca(2+) and actin microfilaments (F-actin), respectively. We show that the ROP1 activity oscillates in a similar phase with the apical F-actin but apparently ahead of tip-localized Ca(2+). Furthermore, our observations support the hypothesis that the oscillation of tip-localized ROP activity and ROP-dependent tip growth in pollen tubes is modulated by the two temporally coordinated downstream pathways, an early F-actin assembly pathway and a delayed Ca(2+) gradient-forming pathway. To our knowledge, our report is the first to demonstrate the oscillation of Rho GTPase signaling, which may be a common mechanism underlying the oscillation of actin-dependent processes such as polar growth, cell movement, and chemotaxis

Root avoidance of toxic metals requires the GeBP-LIKE 4 transcription factor in Arabidopsis thaliana

Plants reorganize their root architecture to avoid growth into unfavorable regions of the rhizosphere. In a screen based on chimeric repressor gene-silencing technology, we identified the Arabidopsis thaliana GeBP-LIKE 4 (GPL4) transcription factor as an inhibitor of root growth that is induced rapidly in root tips in response to cadmium (Cd). We tested the hypothesis that GPL4 functions in the root avoidance of Cd by analyzing root proliferation in split medium, in which only half of the medium contained toxic concentrations of Cd. The wild-type (WT) plants exhibited root avoidance by inhibiting root growth in the Cd side but increasing root biomass in the control side. By contrast, GPL4-suppression lines exhibited nearly comparable root growth in the Cd and control sides and accumulated more Cd in the shoots than did the WT. GPL4 suppression also altered the root avoidance of toxic concentrations of other essential metals, modulated the expression of many genes related to oxidative stress, and consistently decreased reactive oxygen species concentrations. We suggest that GPL4 inhibits the growth of roots exposed to toxic metals by modulating reactive oxygen species concentrations, thereby allowing roots to colonize noncontaminated regions of the rhizosphere

Flexible electronics based on one-dimensional and two-dimensional hybrid nanomaterials

Research on flexible or wearable electronics has been grown remarkably due to theadvent of nanomaterials, such as metal nanowires, graphene, or transition metaldichalcogenides. Although each nanomaterial has mechanical and electrical charac-teristics that can be applied into flexible electronics, the limitations of each nano-material are also clear. In order to overcome the limitations of these nanomaterials,research on the hybrid structures of nanomaterials has been extensively conducted.In this study, we introduce the properties of one-dimensional nanomaterials, two-dimensional nanomaterials, and their hybrid nanomaterials. And then, we provideinformation concerning various flexible electronics based on these nanomaterials.11Nsciescopu

Amorphous Oxide Semiconductor Transistors with Air Dielectrics for Transparent and Wearable Pressure Sensor Arrays

Flexible, transparent pressure sensors have numerous potential applications in wearable electronics, soft robotics, health monitoring. In particular, highly sensitive and reliable pressure sensors that cover wide ranges of pressures are promising because they can undergo various external stimulations. Here an unconventional approach is presented for fabricating the active-matrix array of air-dielectric, amorphous oxide semiconductor transistors for transparent, wearable pressure sensors. In the structure of these pressure-sensitive field-effect transistors (FETs), the clean interface between the air and the oxide semiconductor channel enables the FETs to have outstanding mobility and negligible electrical hysteresis with rapid and reliable responses as pressure sensors for an extensive range of pressures from 200 Pa to 5 MPa. Also, low processing temperature and high transparency of oxide semiconductors make it possible to fabricate them on plastics with flexibility and transparency. The fabrication of active-matrix pressure sensor arrays demonstrated the real-time monitoring of freely moving, ultralight, liquid droplets on the sensor. In addition, this can be integrated into the fingertips of gloves to monitor the pressure changes that occur during grasping objects. These results illustrate the potential of pressure sensors to provide robust solutions in the next-generation electronics including remote surgery, health monitoring, and robotics

Degradation Kinetics of Trichloroethylene by Methylosinus trichosporium PP358

Degradation kinetics of trichloroethylene(TCE) by the resting-cell of the mathanotroph Methylosinus trichosporium PP358 was studied. When 20 mM formate was present in the reaction mixture as a reducing agent, the rate of TCE degradation followed the Michaelis-Menten kinetics and the maximum specific degradation rate(Vmax) and saturation constant (Km) were 14.0 nmol/min??mg cell and 124 ??M, respectively. Methane and methanol inhibited the TCE degradation in a competitive mode and their inhibition constants(Ki) were estimated to be 107 ??M and 3.4 mM, respectively. In the absence of formate, methane and methanol showed a more complex effect on the TCE degradation. At low concentrations, both substrates stimulated the degradation, while at high concentrations, they inhibited the degradation. The maximum specific degradation rate with methane or methanol was about 60 % or 80 % of the maximum specific degradation rate obtainable with added formate. Kinetic equations describing the complex effect of methane or methanol were proposed and the relevant kinetic constants were determined