Search

Summary: Biological nitrogen fixation catalyzed by nitrogenase contributes greatly to the global nitrogen cycle. Nitrogenase expression is subject to regulation in response to nitrogen availability. However, the mechanism through which the transcriptional activator NifA regulates nitrogenase expression by interacting with PII nitrogen regulatory proteins remains unclear in diazotrophic proteobacteria lacking NifL. Here, we demonstrate that in Rhodopseudomonas palustris grown with ammonium, NifA bound deuridylylated PII proteins to form an inactive NifA-PII complex, thereby inhibiting the expression of nitrogenase. Upon nitrogen limitation, the dissociation of uridylylated PII proteins from NifA resulted in the full restoration of NifA activity, and, simultaneously, uridylylation of the significantly up-regulated PII protein GlnK2 led to the increased expression of NifA in R. palustris. This insight into how NifA interacts with PII proteins and controls nitrogenase expression sets the stage for creating highly efficient diazotrophs, reducing the need for energy-intensive chemical fertilizers and helping to diminish carbon emissions.

The support stiffness of the turbopump rotor system with angular contact ball bearing varies with the rotational speed, which leads to the inaccurate prediction of the dynamics of the turbopump rotor system. The model of the rotor bearing system was constructed based on the theoretical model of angular contact ball bearing stiffness, and the dynamics characteristics of the turbopump system were calculated. To verify the accuracy of the stiffness and the dynamics model, a test system of the turbopump rotor with angular contact ball bearings was designed. Since the bearing stiffness cannot be measured directly, a stiffness identification model was introduced, and an unbalanced response test was conducted to verify the dynamics model. It was found that the turbopump bearing stiffness increased dynamically with speed and reduced the unbalance response of the rotor. The results show that the angular contact ball bearing stiffness model and the dynamics model of the rotor support system are accurate and provide support for the dynamics design of the turbopump rotor system with angular contact ball bearings.

Strawberry is an extensively planted horticulture crop with multiple economic values. Vacuolar phosphate transporter (FaVPT1) can promote phosphate and sugar accumulation and improve strawberry fruit quality, however, its transcription regulatory mechanism remains unknown. Here, we report a GRAS superfamily transcription factor (TF) SCARECROW-LIKE8 (FaSCL8) which regulates FaVPT1 expression to control strawberry fruit ripening and quality. The promoter of FaVPT1 was used as a bait to screen the octoploid strawberry cDNA library by yeast one hybrid to obtain the candidate TFs including FaSCL8. FaSCL8 was located in the nucleus and was mainly expressed in fruit, its expression level was increased rapidly during ripening, and induced by exogenous phytohormones including ABA, GA, IAA, and ethylene, as well as sucrose. FaSCL8 can directly combine with the FaVPT1 promoter and regulate its expression in vitro and in vivo. The results of Agrobacterium-mediated transient infection of strawberry fruits showed that overexpression of FaSCL8 could increase soluble sugar, anthocyanin, and phosphorus content, promoting fruit ripening, while decreasing expression of FaSCL8 showed the opposite phenotype. The expression levels of fruit ripening and quality-related genes including FaVPT1, were improved in the over-expressed fruits of FaSCL8, while receded in the FaSCL8-silenced fruits. In conclusion, this study found that FaSCL8 can regulate FaVPT1 expression to improve phosphorus and sugar accumulation in strawberry fruits and promote fruit ripening, providing a new regulation mechanism of strawberry fruit ripening by phosphorus, a macroelement key to fruit quality improvement.

Abstract Background Diabetes mellitus (DM) and cardiovascular diseases often co-exist. Today, percutaneous coronary intervention (PCI) is the preferred revascularization procedure for majority of patients with coronary artery disease. Polymer-free amphilimus-eluting stents (AES) represent a novel elution technology in the current era of drug-eluting stents. In this analysis, we aimed to systematically compare the cardiovascular outcomes which are associated with polymer-free amphilimus-eluting stents (AES) versus the durable polymer zotarolimus-eluting stents (ZES) for the treatment of patients with DM. Methods Http://www.ClinicalTrials.gov, EMBASE, Web of Science, MEDLINE, Cochrane database and Google Scholar were searched for publications comparing polymer-free AES versus durable polymer ZES in patients with DM. Selective cardiovascular outcomes were assessed. Statistical analysis was carried out by the latest version of the RevMan software. Risk ratio (RR) with 95% confidence interval (CI) was used to represent the data analysis. Results Four studies with a total number of 1795 participants with DM whereby 912 patients were assigned to be revascularized by the polymer-free AES and 883 patients were assigned to be revascularized by the durable polymer ZES were included in this analysis. In patients with DM, at one year, polymer-free AES were associated with significantly lower risk of major adverse cardiac events (MACEs) (RR: 0.69, 95% CI: 0.54–0.88; P = 0.002) and target lesion failure (TLF) (RR: 0.66, 95% CI: 0.48–0.91; P = 0.01) compared to durable polymer ZES. However, there was no significant change in all-cause mortality (RR: 0.79, 95% CI: 0.51–1.22; P = 0.28), cardiac death and the other cardiovascular outcomes. Similar risk of total stent thrombosis (RR: 1.13, 95% CI: 0.60–2.13; P = 0.70), including definite stent thrombosis (RR: 1.12, 95% CI: 0.38–3.31; P = 0.84), probable stent thrombosis (RR: 0.87, 95% CI: 0.37–2.09; P = 0.76), possible stent thrombosis (RR: 1.19, 95% CI: 0.50–2.87; P = 0.69) and late stent thrombosis (RR: 1.00, 95% CI: 0.17–5.72; P = 1.00) as between polymer-free AES and durable polymer ZES in patients with DM. Conclusions At 1 year follow-up, polymer-free AES were associated with significantly lower MACEs and TLF compared to durable polymer ZES in these patients with DM, without any increase in mortality, stent thrombosis and other cardiovascular outcomes. However, this analysis is only based on a follow-up time period of one year, therefore, future research should focus on the long term follow-up time period.

Robust DUT-67 was synthesized by the hydrothermal method and characterized by powder X-ray diffraction (PXRD), scanning electron microscopy (SEM), and thermogravimetric analysis (TGA). To systematically study the removal of Cr(VI) ion by DUT-67, single-factor, competition ion, material regeneration, kinetic, and thermodynamic experiments were designed. The experimental results show that DUT-67 had a maximum removal rate of 96.1% and a maximum adsorption capacity of 105.42 mg g−1 with material regeneration and outstanding selective adsorption. In addition, the process of removal of the Cr(VI) ion from an aqueous solution by DUT-67, which accorded with the pseudo-second-order kinetics model and Langmuir model, was studied, and its adsorption mechanism was reasonably explained by the theoretical calculation.

With the increase in deployment of scientific workflow applications on an IaaS cloud computing environment, the distribution of workflow tasks to particular cloud instances to decrease runtime and cost has emerged as an important challenge. The cloud workflow scheduling is a well-known NP-hard problem. In this paper, we propose a new approach for multi-objective workflow scheduling in IaaS clouds offering a limited amount of instances and a flexible combination of instance types, and present a hybrid algorithm combining genetic algorithm, artificial bee colony optimization and decoding heuristic for scheduling workflow tasks over the available cloud resources while trying to optimize the workflow makespan and cost simultaneously. The proposed algorithm is evaluated for real-world scientific applications by a simulation process. The simulation results show that our proposed scheduling algorithm performs better than the current state-of-the-art algorithms. We validate the results by the Wilcoxon signed-rank test.

Prompted by the remarkable progress in both cloud computing and GPU virtualization, cloud gaming has become increasingly more popular in the gaming industry. In cloud gaming, games are stored and run on cloud servers and the gamers interact with games through thin clients. Cloud gaming service providers generally employ multiple geographically distributed data centers to deliver their services. The main challenge for cloud gaming service providers is to find the best tradeoff between two contradicting objectives: reducing the infrastructure operating costs and increasing the quality of player's experience. In this paper, we address a virtual machine provisioning problem for multiplayer cloud gaming with the objective of minimizing both the inter-player delay among interacting players and the electricity costs of cloud gaming service providers, while providing the good-enough response delay to gamers. We formulate the problem into a constrained multiobjective optimization problem and propose an improved grey wolf algorithm to solve the problem. The performance of our proposed algorithm are assessed by simulation experiments based on the real-world parameters. The results show the superior performance of the proposed approach in comparison with the state-of-the-art approaches applied to similar problems.

Abstract The conserved cell division protein SepF aligns polymers of FtsZ, the key cell division protein in bacteria, during synthesis of the (Fts)Z-ring at midcell, the first stage in cytokinesis. In addition, SepF acts as a membrane anchor for the Z-ring. Recently, it was shown that SepF overexpression in Mycobacterium smegmatis blocks cell division. Why this is the case is not known. Surprisingly, we found in Bacillus subtilis that SepF overproduction does not interfere with Z-ring assembly, but instead blocks assembly of late division proteins responsible for septum synthesis. Transposon mutagenesis suggested that SepF overproduction suppresses the essential WalRK two-component system, which stimulates expression of ftsZ. Indeed, it emerged that SepF overproduction impairs normal WalK localization. However, transcriptome analysis showed that the WalRK activity was in fact not reduced in SepF overexpressing cells. Further experiments indicated that SepF competes with EzrA and FtsA for binding to FtsZ, and that binding of extra SepF by FtsZ alleviates the cell division defect. This may explain why activation of WalRK in the transposon mutant, which increases ftsZ expression, counteracts the division defect. In conclusion, our data shows that an imbalance in early cell division proteins can interfere with recruitment of late cell division proteins.

Within bacterial populations, genetically identical cells often behave differently. Single-cell measurement methods are required to observe this heterogeneity. Flow cytometry and fluorescence light microscopy are the primary methods to do this. However, flow cytometry requires reasonably strong fluorescence signals and is impractical when bacteria grow in cell chains. Therefore fluorescence light microscopy is often used to measure population heterogeneity in bacteria. Automatic microscopy image analysis programs typically use phase contrast images to identify cells. However, many bacteria divide by forming a cross-wall that is not detectable by phase contrast. We have developed 'ChainTracer', a method based on the ImageJ plugin ObjectJ. It can automatically identify individual cells stained by fluorescent membrane dyes, and measure fluorescence intensity, chain length, cell length, and cell diameter. As a complementary analysis method we developed 'NucTracer', which uses DAPI stained nucleoids as a proxy for single cells. The latter method is especially useful when dealing with crowded images. The methods were tested with Bacillus subtilis and Lactococcus lactis cells expressing a GFP-reporter. In conclusion, ChainTracer and NucTracer are useful single cell measurement methods when bacterial cells are difficult to distinguish with phase contrast.

Poly(3-hydroxypropionate) (P3HP) is a biodegradable and biocompatible thermoplastic. In our previous study, a pathway for P3HP production was constructed in recombinant Esecherichia coli. Seven exogenous genes in P3HP synthesis pathway were carried by two plasmid vectors. However, the P3HP production was severely suppressed by strain instability due to plasmid loss. In this paper, two strategies, chromosomal gene integration and plasmid addiction system (PAS) based on amino acid anabolism, were applied to construct a genetically stable strain. Finally, a combination of those two methods resulted in the best results. The resultant strain carried a portion of P3HP synthesis genes on chromosome and the others on plasmid, and also brought a tyrosine-auxotrophy based PAS. In aerobic fed-batch fermentation, this strain produced 25.7 g/L P3HP from glycerol, about 2.5-time higher than the previous strain with two plasmids. To the best of our knowledge, this is the highest P3HP production from inexpensive carbon sources.

This study investigates the relationship between board nationality diversity (BND) and environmental, social, and governance (ESG) in developing countries. It also highlights the role of legitimacy concerns in investigating how foreign ownership moderates the connection between BND and ESG due to the increased liability of foreignness. Using a sample of listed firms in Johannesburg stock exchange (JSE) in South Africa over 2015--2020, our two-step system GMM findings show that board nationality diversity positively affects ESG. Moreover, our study found that foreign ownership strengthens the positive connection between BND and ESG. Our study contributes to the literature by highlighting the importance of legitimacy theory in the dynamic nexus between BND and ESG. The findings of this study have substantial implications for firms, investors, and stakeholders. [ABSTRACT FROM AUTHOR]