Engineering a mevalonate pathway in Halomonas bluephagenesis for the production of lycopene

IntroductionRed-colored lycopene has received remarkable attention in medicine because of its antioxidant properties for reducing the risks of many human cancers. However, the extraction of lycopene from natural hosts is limited. Moreover, the chemically synthesized lycopene raises safety concerns due to residual chemical reagents. Halomonas bluephagenesis is a versatile chassis for the production of fine chemicals because of its open growth property without sterilization.MethodsA heterologous mevalonate (MVA) pathway was introduced into H. bluephagenesis strain TD1.0 to engineer a bacterial host for lycopene production. A pTer7 plasmid mediating the expression of six MVA pathway genes under the control of a phage PMmp1 and an Escherichia coli Ptrc promoters and a pTer3 plasmid providing lycopene biosynthesis downstream genes derived from Streptomyces avermitilis were constructed and transformed into TD1.0. The production of lycopene in the engineered H. bluephagenesis was evaluated. Optimization of engineered bacteria was performed to increase lycopene yield.ResultsThe engineered TD1.0/pTer7-pTer3 produced lycopene at a maximum yield of 0.20 mg/g dried cell weight (DCW). Replacing downstream genes with those from S. lividans elevated the lycopene production to 0.70 mg/g DCW in the TD1.0/pTer7-pTer5 strain. Optimizing the PMmp1 promoter in plasmid pTer7 with a relatively weak Ptrc even increased the lycopene production to 1.22 mg/g DCW. However, the change in the Ptrc promoter in pTer7 with PMmp1 did not improve the yield of lycopene.ConclusionWe first engineered an H. bluephagenesis for the lycopene production. The co-optimization of downstream genes and promoters governing MVA pathway gene expressions can synergistically enhance the microbial overproduction of lycopene

Monitoring Level Fluctuations of the Lakes in the Yangtze River Basin from Radar Altimetry

Water level variations in four natural lakes, Poyang, Dongting, Tai, and Chao, within the Yangtze River basin are studied using ENVISAT GDRs. The GDRs were edited using simple editing criteria and appropriate geophysical corrections applied. Altimeter-derived lake level variation time series were then generated and analyzed. The results of this study, which is the first of its kind in using data from ENVISAT missions over the Yangtze River basin in China, reveal that the water level changes in these four lakes directly reflect the water level of the Yangtze River and contribute to the floods and their associated disasters that usually occur in the middle and lower reaches of the Yangtze River

Photodynamic Action of LED-Activated Curcumin against Staphylococcus aureus

Aim. To investigate the effect of photodynamic action of LED-activated curcumin on cell viability, membrane permeability, and intracellular reactive oxygen species of Staphylococcus aureus. Methods. Staphylococcus aureus was incubated with the different concentrations of curcumin for 60 min and then irradiated by blue light with the wavelength of 470 nm and with light dose of 3 J/cm2. The colony forming unit assay was used to investigate photocytotoxicity of curcumin on Staphylococcus aureus, confocal laser scanning microscopy (CLSM) and flow cytometry (FCM) for assaying membrane permeability, FCM analysis with DCFH-DA staining for measuring the intracellular ROS level, and transmission electron microscopy (TEM) for observing morphology and structure. Results. Blue light-activated curcumin significantly killed Staphylococcus aureus in a curcumin dose-dependent manner. TEM observed remarkable structural damages in S. aureus after light-activated curcumin. More red fluorescence of PI dye was found in S. aureus treated by blue light-activated curcumin than in those of the controlled bacterial cells. Intracellular ROS increase was observed after light-activated curcumin. Conclusion. Blue light-activated curcumin markedly damaged membrane permeability, resulting in cell death of Staphylococcus aureus and highlighted that intracellular ROS increase might be an important event in photodynamic killing of Staphylococcus aureus in the presence of curcumin

The enormous repetitive Antarctic krill genome reveals environmental adaptations and population insights

Antarctic krill (Euphausia superba) is Earth’smost abundant wild animal, and its enormous biomass is vital to the Southern Ocean ecosystem. Here, we report a 48.01-Gb chromosome-level Antarctic krill genome, whose large genome size appears to have resulted from inter-genic transposable element expansions. Our assembly reveals the molecular architecture of the Antarctic krill circadian clock and uncovers expanded gene families associated with molting and energy metabolism, providing insights into adaptations to the cold and highly seasonal Antarctic environment. Population-level genome re-sequencing from four geographical sites around the Antarctic continent reveals no clear population structure but highlights natural selection associated with environmental variables. An apparent drastic reduction in krill population size 10 mya and a subsequent rebound 100 thousand years ago coincides with climate change events. Our findings uncover the genomic basis of Antarctic krill adaptations to the Southern Ocean and provide valuable resources for future Antarctic research

Signal Control Method for Through and Left-Turn Shared Lane by Setting Left-Turn Waiting Area at Signalized Intersections

This paper proposes a signal control method for the through and left-turn shared lanes at signalized intersections to solve traffic conflicts between left-turn vehicles and opposing through vehicles by setting left-turn waiting area (LWA). Delays and stops are weighted to form an integrated performance index (PI) in a vehicle-to-infrastructure cooperation system. The PI models pertaining to all vehicles are established based on the LWA intersection. In addition, an optimized method of signal timing parameters is constructed by minimizing the average PI. VISSIM simulation shows that the average PI decreases by 6.51% compared with the original layout and signal timing plan of the intersection, since the increased delay of the side-road left-turn vehicles is insufficient to offset the reduced delay of the side-road through vehicles after the improvement. The sensitivity analysis shows that the greater the traffic volume of the phase including the through and left-turn shared lanes, the higher the operation efficiency of the LWA intersection compared with the typical permitted phase intersection. When the left-turn vehicles of the shared lanes in each cycle are less than the stop spaces, the LWA intersection can effectively reduce the average PI of the shared lanes. Furthermore, the more the stop spaces in the LWA, the lower the average PI in the same traffic conditions

Dynamic Phase Signal Control Method for Unstable Asymmetric Traffic Flow at Intersections

This paper addresses the limitations that the phases proposed in variable phase sequencing studies for stochastic traffic flow are all predetermined and that the variable phase sequencing is only suitable for low traffic volume environment. It presents a dynamic phase signal control method for unstable asymmetric traffic flow with two primary operational objectives: the realization of a dynamic phase scheme in each cycle and optimization of signal control parameters. First, an asymmetric state of traffic flow at signalized intersections is defined, rules governing the generation of the dynamic phase of each cycle based on asymmetric state are proposed, and the delay variations of intersections adopting dynamic phase schemes are modeled. Next, a signal control parameter adjustment algorithm for the dynamic phase is constructed to maximize the positive benefits of delay variation. Last, the operational performance of the proposed method is validated using data collected from an intersection in Harbin, China, by VISSIM simulation. Furthermore, it is found that a higher asymmetric coefficient leads to lower efficiency of a symmetrical release phase scheme at intersections, and the increase of average delay becomes significant when the asymmetric coefficient threshold is greater than 0.2

Signal Control Method for Through and Left-Turn Shared Lane by Setting Left-Turn Waiting Area at Signalized Intersections

This paper proposes a signal control method for the through and left-turn shared lanes at signalized intersections to solve traffic conflicts between left-turn vehicles and opposing through vehicles by setting left-turn waiting area (LWA). Delays and stops are weighted to form an integrated performance index (PI) in a vehicle-to-infrastructure cooperation system. The PI models pertaining to all vehicles are established based on the LWA intersection. In addition, an optimized method of signal timing parameters is constructed by minimizing the average PI. VISSIM simulation shows that the average PI decreases by 6.51% compared with the original layout and signal timing plan of the intersection, since the increased delay of the side-road left-turn vehicles is insufficient to offset the reduced delay of the side-road through vehicles after the improvement. The sensitivity analysis shows that the greater the traffic volume of the phase including the through and left-turn shared lanes, the higher the operation efficiency of the LWA intersection compared with the typical permitted phase intersection. When the left-turn vehicles of the shared lanes in each cycle are less than the stop spaces, the LWA intersection can effectively reduce the average PI of the shared lanes. Furthermore, the more the stop spaces in the LWA, the lower the average PI in the same traffic conditions

Morphology-Tuned Synthesis of Nickel Cobalt Selenides as Highly Efficient Pt-Free Counter Electrode Catalysts for Dye-Sensitized Solar Cells

In this work, morphology-tuned ternary nickel cobalt selenides based on different Ni/Co molar ratios have been synthesized via a simple precursor conversion method and used as counter electrode (CE) materials for dye-sensitized solar cells (DSSCs). The experimental facts and mechanism analysis clarified the possible growth process of product. It can be found that the electrochemical performance and structures of ternary nickel cobalt selenides can be optimized by tuning the Ni/Co molar ratio. Benefiting from the unique morphology and tunable composition, among the as-prepared metal selenides, the electrochemical measurements showed that the ternary nickel cobalt selenides exhibited a more superior electrocatalytic activity in comparison with binary Ni and Co selenides. In particular, the three-dimensional dandelion-like Ni_0.33Co_0.67Se microspheres delivered much higher power conversion efficiency (9.01%) than that of Pt catalyst (8.30%) under AM 1.5G irradiation

Effects of 24-Epibrassinolide, melatonin and their combined effect on cadmium tolerance in Primula forbesii Franch

This study aimed to investigate the interaction between 24-Epibrassinolide (EBR) and melatonin (MT) and their effects on cadmium (Cd)-stressed Primula forbesii Franch. P. forbesii seedlings were hydroponically acclimatized at 6–7 weeks, then treated with Cd (200 μmol L–1), 24-EBR (0.1 μmol L–1), and MT (100 μmol L–1) after two weeks. Cd stress significantly reduced crown width, shoot, root length, shoot fresh weight, and fresh and dry root weights. Herein, 24-EBR, MT, and 24-EBR+MT treatments attenuated the growth inhibition caused by Cd stress and improved the morphology, growth indexes, and ornamental characteristics of P. forbesii under Cd stress. 24-EBR had the best effect by effectively alleviating Cd stress and promoting plant growth and development. 24-EBR significantly increased all growth parameters compared to Cd treatment. In addition, 24-EBR significantly improved the gas exchange parameters, activities of antioxidant enzymes, and the cycle efficiency of AsA-GSH. Furthermore, 24-EBR increased the activities of ascorbate peroxidase (APX), glutathione reductase (GR), dehydroascorbate reductase (DHAR), and monodehydroascorbate reductase (MDHAR) by 127.29%, 61.31%, 61.22%, and 51.04%, respectively, compared with the Cd treatment. Therefore, 24-EBR removed the reactive oxygen species produced by stress, thus protecting plants against stress damage. These results indicate that 24-EBR can effectively enhance the tolerance of P. forbesii to Cd stress

X-band two-stage rf pulse compression system with correction cavity chain

A compact X-band two-stage rf pulse compression system has been successfully designed, fabricated, and tested at Tsinghua X-band high-power test stand. The pulse compression system consists of a correction cavity chain, a first-stage, and a second-stage storage cavity. The correction cavity chain adopts a new design whose transmission loss and length are reduced by half compared with the old one. A detuning device is applied to the second-stage storage cavity so that the system can work in one-stage or alternatively two-stage compression mode. In the one-stage compression mode, a 150-ns, 70-MW flattop output, with a standard deviation of 1.5% in amplitude and 1° in phase, was generated with a gain factor of 3. In the two-stage compression mode, a first two-stage pulse compression experiment with correction cavities in the X band was performed. A peak power of 320 MW was achieved with a gain factor of 9.7 and full-width at half-maximum pulse durations of 53 ns