Multiple Metabolic Phenotypes as Screening Criteria Are Correlated With the Plant Growth-Promoting Ability of Rhizobacterial Isolates

Efficient screening method is the prerequisite for getting plant growth-promoting (PGP) rhizobacteria (PGPR) which may play an important role in sustainable agriculture from the natural environment. Many current traditional preliminary screening criteria based on knowledge of PGP mechanisms do not always work well due to complex plant–microbe interactions and may lead to the low screening efficiency. More new screening criteria should be evaluated to establish a more effective screening system. However, the studies focused on this issue were not enough, and few new screening criteria had been proposed. The aim of this study was to analyze the correlation between the metabolic phenotypes of rhizobacterial isolates and their PGP ability. The feasibility of using these phenotypes as preliminary screening criteria for PGPR was also evaluated. Twenty-one rhizobacterial isolates were screened for their PGP ability, traditional PGP traits, and multiple metabolic phenotypes that are not directly related to PGP mechanisms, but are possibly related to rhizosphere colonization. Correlations between the PGP traits or metabolic phenotypes and increases in plant agronomic parameters were analyzed to find the indicators that are most closely related to PGP ability. The utilization of 11 nutrient substrates commonly found in root exudates, such as D-salicin, β-methyl-D-glucoside, and D-cellobiose, was significantly positively correlated with the PGP ability of the rhizobacterial isolates. The utilization of one amino acid and two organic acids, namely L-aspartic acid, α-keto-glutaric acid, and formic acid, was negatively correlated with PGP ability. There were no significant correlations between four PGP traits tested in this study and the PGP ability. The ability of rhizobacterial isolates to metabolize nutrient substrates that are identical or similar to root exudate components may act as better criteria than PGP traits for the primary screening of PGPR, because rhizosphere colonization is a prerequisite for PGPR to affect plants.

Numerical simulation of particle screening efficiency of large multi-layer vibrating screen based on discrete element method

With the increasing requirements for energy conservation and environmental protection, multi-layer vibrating screens have become hot issues. Compared with single-layer vibrating screens, multi-layer vibrating screens has much better performance in terms of processing effect, treatment capacity, and environmental protection. The research on the physical parameters of the multi-layer vibrating screen is of great significance to the actual production. However, analysis and simulation studies of multi-layer vibrating screens are limited. In this paper, the screening process of wet particles on a multi-layer vibrating screen was simulated by using the discrete element method. The characteristics and application scope of the two vibration modes were analyzed. The particle penetration rate, the number of collisions, and the distribution of the particles under 23 combinations of structures and vibration parameters were investigated. The influence of different parameters on screening performance was analyzed. Several optimal combinations of frequency, amplitude and screen inclination angle under different working conditions were obtained. The screening efficiency of the balanced elliptic motion is higher than that of the linear motion. The best combination of the three parameters is 4 mm amplitude, 20 Hz frequency, and 3° inclination angle. The efficiency is higher when the particles follow a distribution of arithmetic on the screen. This study provides a reference for the efficient operation and optimal design of large multi-layer screening equipment.

Agent-Based Simulation of Virus Testing in Certain-Exposure Time through Community Health Service Centers’ Evaluation—A Case Study of Wuhan

Short-term and large-scale full-population virus testing is crucial in containing the spread of the COVID-19 pandemic in China. However, the uneven distribution of health service facilities in terms of space and size may lead to prolonged crowding during testing, thus increasing the chance of virus cross-infection. Therefore, appropriate control of crowd exposure time in large-scale virus testing should be an important goal in the layout of urban community health facilities. This paper uses the Quanta concept and Wells-Riley model to define the “certain-exposure time” under low cross-infection rate. Then, an agent-based simulation model was used to simulate the reasonable screening efficiency of community health service facilities during certain-exposure time at different stages of the COVID-19 pandemic and under different screening processes. Eventually, the screening efficiency was evaluated for all community health service centers in Wuhan. During the early period of the pandemic, 23.13% of communities failed to complete virus testing of community residents within 2 h of certain-exposure time, leaving approximately 56.07% of the population unscreened; during the later period of the COVID-19 pandemic, approximately 53% of communities and 75% of residents could not be screened. The results can pinpoint the distribution of community health service centers with inadequate screening capacity, facilitate targeted policymaking and planning, and effectively curb COVID-19 cross-infection during screening.

A high throughput bispecific antibody discovery pipeline

Bispecific antibodies (BsAbs) represent an emerging class of immunotherapy but inefficiency in the current BsAb discovery paradigm has limited their broad clinical availability. Here we report a high throughput, agnostic, single-cell-based BsAb functional screening pipeline, comprising molecular and cell engineering for efficient generation of BsAb library cells, followed by functional interrogation at the single-cell level to identify and sort positive clones and downstream sequence identification with single-cell PCR and sequencing and functionality characterization. Using a CD19xCD3 bispecific T cell engager (BiTE) as a model system, we demonstrate that our single cell platform possesses a high throughput screening efficiency of up to one and half million variant library cells per run and can isolate rare functional clones at low abundance of 0.008%. Using a complex CD19xCD3 BiTE-expressing cell library with approximately 22,300 unique variants comprising combinatorially varied scFvs, connecting linkers and VL/VH orientations, we have identified 98 unique clones including extremely rare ones (∼ 0.001% abundance). We also discovered BiTEs that exhibit novel properties contradictory to conventional wisdom, including harboring rigid scFv connecting peptide linkers yet with in vitro cytotoxicity comparable to that of clinically approved Blinatumomab. Through sequencing analyses on sorted BiTE clones, we discovered multiple design variable preferences for functionality including the CD19VL-VH– CD3VH-VL and CD19VH-VL–CD3VH-VL arrangements being the most favored orientation. Sequence analysis further interrogated the sequence composition of the CDRH3 domain in scFvs and identified amino acid residues conserved for function. We expect our single cell platform to not only significantly increase the development speed of high quality of new BsAb therapeutics for cancer and other disorders, but also enable identifying generalizable design principles for new BsAbs and other immunotherapeutics based on an in-depth understanding of the inter-relationships between sequence, structure, and function.

Study on screening performance and parameter optimization of vibrating-dewatering screen

In this paper, the dewatering and screening process of vibrating-dewatering screen is studied by the combination of simulation test and physical experiment. The simulation model of dewatering screening process is established by the method of computational fluid dynamics (CFD) and discrete element method (DEM). Subsequently, the screening efficiency and processing efficiency are defined as evaluating indexes for performance of dewatering and screening. Four parameters of amplitude, vibration frequency, vibrating direction angle and slope angle of screen surface are selected for single factor simulation test, and the variation of dewatering and screening performance under different parameters is obtained. Finally, the reliability of the simulation results is verified by the physical experiment platform, and significant factors affecting the evaluation index of the vibrating-dewatering screen parameters and the optimal parameter combination are obtained by orthogonal test.

Study of Double-Deck Vibrating Flip-Flow Screen Based on Dynamic Stiffness Characteristics of Shear Springs

Double-deck vibrating flip-flow screens have been widely used for the repurposing of decoration waste; however, the influence of shear spring stiffness on the screen’s vibration characteristics is under-researched. The shear spring stiffness affects the amplitude–frequency characteristics, phase–frequency characteristics, screening performance and processing capacity of the screen. In this paper, a mathematical model of the double-deck vibrating flip-flow screen is proposed based on a vibrating system with three degrees of freedom. Based on the experiments of the industrial screen, the amplitude–frequency and phase–frequency characteristics of the double-deck vibrating flip-flow screen were studied. Within the range of 25 to 75 rad/s, the amplitude of the main screen frame decreased gradually, the floating screen frames decreased at first and then increased and the amplitudes of the main and floating screen frames were dependent on the stiffness of the isolation springs and shear springs. When the frequency was 75 rad/s, the stiffness of the upper and lower shear springs was 11,440 kN/m, respectively, and the screening efficiency reached 97.09%.