Carbonate precipitation induced by microorganisms has become a hot topic in the field of carbonate sedimentology, although the effects of magnesium on biomineral formation have rarely been studied. In experiments described here, magnesium sulfate and magnesium chloride were used to investigate the significant role played by Mg2+ on carbonate precipitation. In this study, Staphylococcus epidermidis Y2 was isolated and identified by 16S ribosomal DNA (rDNA) homology comparison and ammonia, pH, carbonic anhydrase, carbonate, and bicarbonate ions were monitored during laboratory experiments. The mineral phase, morphology, and elemental composition of precipitates were analyzed by XRD and SEM-EDS. Ultrathin slices of bacteria were analyzed by HRTEM-SAED and STEM. The results show that this bacterium releases ammonia and carbonic anhydrase to increase pH, and raise supersaturation via the large number of carbonate and bicarbonate ions that are released through carbon dioxide hydration catalyzed by carbonic anhydrase. The crystal cell density of monohydrocalcite is lower in a magnesium chloride medium, compared to one of magnesium sulfate. Crystals grow in the mode of a spiral staircase in a magnesium sulfate medium, but in a concentric circular pattern in a magnesium chloride medium. There was no obvious intracellular biomineralization taking place. The results presented here contribute to our understanding of the mechanisms of biomineralization, and to the role of Mg2+ in crystal form.

This is the first evidence that SiHAK1 acts as a K transporter and is modulated by internal and external K, which expands our understanding of the significant physiological roles of large HAK/KUP/KT transporters in crops. Crop genomes have shown the richness of K transporters in HAK/KUP/KT (High Affinity K/K Uptake Proteins/K Transporter) family, and much progress have been achieved toward understanding the diverse roles of K uptake and translocation, and abiotic stresses resistance in this family. The HAK/KUP/KT family has increasingly been recognized to be at a pivotal status in the mediation of K translocation and long-term transport; however, our understanding of the molecular mechanisms remains limited. Foxtail millet is an ideal plant for studying long-distance potassium (K) transport because of its small diploid genome and better adaptability to arid lands. Here, we identified 29 putative HAK/KUP/KT proteins from the Setaria italica genome database. These genes were distributed in seven chromosomes of foxtail millet and divided into five clusters. SiHAK1 exhibited widespread expression in various tissues and significant up-regulation in the shoots under low K condition. SiHAK1 was localized in the cell membrane and low K elicited SiHAK1-meidated high-affinity K uptake activity in Cy162 yeast cells and Arabidopsis athak5 mutants. The transport activity of SiHAK1 was coordinately modulated by external K supply and internal K content in the cell under low K and high salt environment. Our findings reveal the K uptake mechanisms of SiHAK1 and indicated that it may be involved in the mediation of K homeostasis in S. italica under K-deficiency and salt stress.

Objectives To investigate nurses’ behavioral intention toward caring for COVID-19 patients on mechanical ventilation, as well as the factors affecting their intention. Background COVID-19 patients undergoing mechanical ventilation have many care needs and pose more challenges for nurses, which might adversely affect nurses’ intention toward caring behavior. Methods A cross‐sectional study was conducted by using simple random sampling to recruit 598 nurses from five tertiary hospitals in Sichuan Province, China. The participants responded to an online questionnaire that included questions on demographic characteristics; the Attitude, Subjective Norms, and Behavioral Intention of Nurses toward Mechanically Ventilated Patients (ASIMP) questionnaire; the Nursing Professional Identity Scale (NPIS); and the Compassion Fatigue-Short Scale (CF-Short Scale). ANOVA, Spearman correlation analysis, and multiple linear regression were performed to analyze the data. Results The mean total behavioral intention score was 179.46 (± 14.83) out of a total score of 189.00, which represented a high level of intention toward caring for patients on mechanical ventilation. Multiple linear regression revealed that subjective norms (β = 0.390, P<0.001), perceived behavioral control (β = 0.149, P<0.001), professional identity (β = 0.101, P = 0.009), and compassion fatigue (β = 0.088 P = 0.024) were significant predictors of nurses’ behavioral intention. Conclusions Most nurses have a positive behavioral intention to care for COVID-19 patients undergoing mechanical ventilation. The findings in this study provide some insight for developing effective and tailored strategies to promote nurses’ behavioral intention toward caring for ventilated patients under the pandemic situation.

Dynamic regulation is an effective strategy for control of gene expression in microbial cell factories. In some pathway contexts, several metabolic modules must be controlled in a time dependent or ordered manner to maximize production, while the creation of genetic circuits with ordered regulation capacity still remains a great challenge. In this work, we develop a pathway independent and programmable system that enables multi-modular ordered control of metabolism in Bacillus subtilis. First, a series of thermosensors were created and engineered to expand their thresholds. Then we designed single-input-multi-output circuits for ordered control based on the use of thermosensors with different transition points. Meanwhile, a repression circuit was constructed by combining CRISPRi-based NOT gates. As a proof-of-concept, these genetic circuits were applied for multi-modular ordered control of 2′-fucosyllactose (2′-FL) biosynthesis, resulting in a production of 1839.7 mg/l in shake flask, which is 5.16-times that of the parental strain. In a 5-l bioreactor, the 2′-FL titer reached 28.2 g/l with down-regulation of autolysis. Taken together, this work provides programmable and versatile thermosensitive genetic toolkits for dynamic regulation in B. subtilis and a multi-modular ordered control framework that can be used to improve metabolic modules in other chassis cells and for other compounds.

Potassium retention under saline conditions has emerged as an important determinant for salt tolerance in plants. Halophytic Hordeum brevisubulatum evolves better strategies to retain K+ to improve high-salt tolerance. Hence, uncovering K+-efficient uptake under salt stress is vital for understanding K+ homeostasis. HAK/KUP/KT transporters play important roles in promoting K+ uptake during multiple stresses. Here, we obtained nine salt-induced HAK/KUP/KT members in H. brevisubulatum with different expression patterns compared with H. vulgare through transcriptomic analysis. One member HbHAK1 showed high-affinity K+ transporter activity in athak5 to cope with low-K+ or salt stresses. The expression of HbHAK1 in yeast Cy162 strains exhibited strong activities in K+ uptake under extremely low external K+ conditions and reducing Na+ toxicity to maintain the survival of yeast cells under high-salt-stress. Comparing with the sequence of barley HvHAK1, we found that C170 and R342 in a conserved domain played pivotal roles in K+ selectivity under extremely low-K+ conditions (10 μM) and that A13 was responsible for the salt tolerance. Our findings revealed the mechanism of HbHAK1 for K+ accumulation and the significant natural adaptive sites for HAK1 activity, highlighting the potential value for crops to promote K+-uptake under stresses.