Elevated Membrane Potential as a Tetracycline Resistance Mechanism in Escherichia coli.

The metabolic environment is responsible for antibiotic resistance, which highlights the way in which the antibiotic resistance mechanism works. Here, GC-MS-based metabolomics with iTRAQ-based proteomics was used to characterize a metabolic state in tetracycline-resistant Escherichia coli K12 (E. coli-RTET) compared with tetracycline-sensitive E. coli K12. The repressed pyruvate cycle against the elevation of the proton motive force (PMF) and ATP constructed the most characteristic feature as a consequence of tetracycline resistance. To understand the role of the elevated PMF in tetracycline resistance, PMF inhibitor carbonyl cyanide 3-chlorophenylhydrazone (CCCP) and the pH gradient were used to investigate how the elevation influences bacterial viability and intracellular antibiotic concentration. A strong synergy was detected between CCCP and tetracycline to the viability, which was consistent with increasing intracellular drug and decreasing external pH. Furthermore, E. coli-RTET and E. coli-RGEN with high and low PMF concentrations were susceptible to gentamicin and tetracycline, respectively. The elevated PMF in E. coli-RTET was attributed to the activation of other metabolic pathways, except for the pyruvate cycle, including a malate-oxaloacetate-phosphoenolpyruvate-pyruvate-malate cycle. These results not only revealed a PMF-dependent mechanism for tetracycline resistance but also provided a solution to tetracycline-resistant pathogens by aminoglycosides and aminoglycoside-resistant bacteria by tetracyclines.

Personality traits predict treatment outcome of an antidepressant in untreated adolescents with depression: An 8-week, open-label, flexible-dose study.

BACKGROUND: Antidepressant response in adults with major depressive disorder (MDD) is probably influenced by personality dimensions. However, personality dimensions in depression and their association with antidepressant treatment in adolescents are relatively unknown. We sought to investigate whether personality traits (PTs) can influence antidepressant treatment response in adolescents with depression. METHODS: Eighty-two adolescents with MDD who had completed the 8 weeks of treatment with selective serotonin reuptake inhibitors (SSRI) were enrolled. The Revised NEO Five-Factor Inventory (NEO-FFI-R) was used to measure their personality at baseline, and the 17-item Hamilton Depression Rating Scale (HAMD-17) and Children's Depression Rating Scale-Revised (CDRS-R) were used to evaluate depressive symptoms at baseline and 8 weeks. Moreover, logistic regression was performed to investigate the relationship between personality dimensions and antidepressant response. Receiver operating characteristic analyses were employed to determine the accuracy of a PT-based model in predicting the antidepressant response rate. RESULTS: Adolescents with MDD had significantly different PTs at baseline. Multivariable logistic regression analysis showed that extroversion scores were associated with response to antidepressant treatment, the lower the extroversion score, the better the response to antidepressant treatment, after correcting for variables with significant differences and trends or all potential confounding variables. It was also found that the combination of disease duration, extraversion-gregariousness, and agreeableness-trust effectively predicted antidepressant response in adolescents with MDD, with a sensitivity of 79.4 % and specificity of 68.7 %. CONCLUSION: Personality dysfunction in adolescents is associated with MDD. The antidepressant treatment response is influenced by the degree of extroversion in adolescents with MDD.

Elevated proton motive force is a tetracycline resistance mechanism that leads to the sensitivity to gentamicin in Edwardsiella tarda.

Tetracycline is a commonly used human and veterinary antibiotic that is mostly discharged into environment and thereby tetracycline-resistant bacteria are widely isolated. To combat these resistant bacteria, further understanding for tetracycline resistance mechanisms is needed. Here, GC-MS based untargeted metabolomics with biochemistry and molecular biology techniques was used to explore tetracycline resistance mechanisms of Edwardsiella tarda. Tetracycline-resistant E. tarda (LTB4-RTET ) exhibited a globally repressed metabolism against elevated proton motive force (PMF) as the most characteristic feature. The elevated PMF contributed to the resistance, which was supported by the three results: (i) viability was decreased with increasing PMF inhibitor carbonylcyanide-3-chlorophenylhydrazone; (ii) survival is related to PMF regulated by pH; (iii) LTB4-RTET were sensitive to gentamicin, an antibiotic that is dependent upon PMF to kill bacteria. Meanwhile, gentamicin-resistant E. tarda with low PMF are sensitive to tetracycline is also demonstrated. These results together indicate that the combination of tetracycline with gentamycin will effectively kill both gentamycin and tetracycline resistant bacteria. Therefore, the present study reveals a PMF-enhanced tetracycline resistance mechanism in LTB4-RTET and provides an effective approach to combat resistant bacteria.

Exogenous pyruvate promotes gentamicin uptake to kill antibiotic-resistant Vibrio alginolyticus.

OBJECTIVES: Elucidating antibiotic resistance mechanisms is necessary for developing novel therapeutic strategies. The increasing incidence of antibiotic-resistant Vibrio alginolyticus infection threatens both human health and aquaculture, but the mechanism has not been fully elucidated. METHODS: Here, an isobaric tags for relative and absolute quantification (iTRAQ) functional proteomics analysis was performed on gentamicin-resistant V. alginolyticus (VA-RGEN) and a gentamicin-sensitive strain in order to characterize the global protein expression changes upon gentamicin resistance. Then, the bacterial killing assay and bacterial gentamicin pharmacokinetics were performed. RESULTS: Proteomics analysis demonstrated a global metabolic downshift in VA-RGEN, where the pyruvate cycle (the P cycle) was severely compromised. Exogenous pyruvate restored the P cycle activity, disrupting the redox state and increasing the membrane potential. It thereby potentiated gentamicin-mediated killing by approximately 3000- and 150-fold in vitro and in vivo, respectively. More importantly, bacterial gentamicin pharmacokinetics indicated that pyruvate enhanced gentamicin influx to a degree that exceeded the gentamicin expelled by the bacteria, increasing the intracellular gentamicin. CONCLUSION: Thus, our study suggests a metabolism-based approach to combating gentamicin-resistant V. algonolyticus, which paves the way for combating other types of antibiotic-resistant bacterial pathogens.

A glucose-mediated antibiotic resistance metabolic flux from glycolysis, the pyruvate cycle, and glutamate metabolism to purine metabolism.

Introduction: Bacterial metabolic environment influences antibiotic killing efficacy. Thus, a full understanding for the metabolic resistance mechanisms is especially important to combat antibiotic-resistant bacteria. Methods: Isobaric tags for relative and absolute quantification-based proteomics approach was employed to compare proteomes between ceftazidime-resistant and -sensitive Edwarsiella tarda LTB4 (LTB4-RCAZ and LTB4-S, respectively). Results: This analysis suggested the possibility that the ceftazidime resistance mediated by depressed glucose is implemented through an inefficient metabolic flux from glycolysis, the pyruvate cycle, glutamate metabolism to purine metabolism. The inefficient flux was demonstrated by the reduced expression of genes and the decreased activity of enzymes in the four metabolic pathways. However, supplement upstream glucose and downstream guanosine separately restored ceftazidime killing, which not only supports the conclusion that the inefficient metabolic flux is responsible for the resistance, but also provides an effective approach to reverse the resistance. In addition, the present study showed that ceftazidime is bound to pts promoter in E. tarda. Discussion: Our study highlights the way in fully understanding metabolic resistance mechanisms and establishing metabolites-based metabolic reprogramming to combat antibiotic resistance.

Aspartate metabolic flux promotes nitric oxide to eliminate both antibiotic-sensitive and -resistant Edwardsiella tarda in zebrafish.

Introduction: Metabolic reprogramming potentiates host protection against antibiotic-sensitive or -resistant bacteria. However, it remains unclear whether a single reprogramming metabolite is effective enough to combat both antibiotic-sensitive and -resistant bacteria. This knowledge is key for implementing an antibiotic-free approach. Methods: The reprogramming metabolome approach was adopted to characterize the metabolic state of zebrafish infected with tetracycline-sensitive and -resistant Edwardsiella tarda and to identify overlapping depressed metabolite in dying zebrafish as a reprogramming metabolite. Results: Aspartate was identify overlapping depressed metabolite in dying zebrafish as a reprogramming metabolite. Exogenous aspartate protects zebrafish against infection caused by tetracycline-sensitive and -resistant E. tarda. Mechanistically, exogenous aspartate promotes nitric oxide (NO) biosynthesis. NO is a well-documented factor of promoting innate immunity against bacteria, but whether it can play a role in eliminating both tetracycline-sensitive and -resistant E. tarda is unknown. Thus, in this study, aspartate was replaced with sodium nitroprusside to provide NO, which led to similar aspartate-induced protection against tetracycline-sensitive and -resistant E. tarda. Discussion: These findings support the conclusion that aspartate plays an important protective role through NO against both types of E. tarda. Importantly, we found that tetracycline-sensitive and -resistant E. tarda are sensitive to NO. Therefore, aspartate is an effective reprogramming metabolite that allows implementation of an antibiotic-free approach against bacterial pathogens.

Analysis of Lysine Acetylation and Acetylation-like Acylation In Vitro and In Vivo.

Protein lysine acetylation refers to the covalent transfer of an acetyl moiety from acetyl coenzyme A to the epsilon-amino group of a lysine residue and is critical for regulating protein functions in almost all living cells or organisms. Studies in the past decade have demonstrated the unexpected finding that acetylation-like acylation, such as succinylation, propionylation, butyrylation, crotonylation, and lactylation, is also present in histones and many non-histone proteins. Acetylation and acetylation-like acylation serve as reversible on/off switches for regulating protein function while interplaying with other post-translational modifications (such as phosphorylation and methylation) in a codified manner. Lysine acetylation and acetylation-like acylation are important for regulating different cellular and developmental processes in normal and pathological states. Thus, the detection of such modifications is important for related basic research and molecular diagnostics. Traditionally, lysine acetylation is detected by autoradiography, but recent decades have seen great improvement in the quality of site-specific antibodies against acetylation (or acetylation-like acylation), thereby providing competitive alternatives to the use of radioactive acetate and acetyl-coenzyme A for in vivo and in vitro labeling, respectively. This article describes protocols for the detection of lysine acetylation and acetylation-like acylation with site-specific antibodies to complement extant autoradiography-based methods (Pelletier et al., 2017). © 2023 Wiley Periodicals LLC. Basic Protocol 1: Acylation assays in vitro Basic Protocol 2: Determination of in vivo acylation.

[Effect of Sertraline on Serum Cytokine Levels in Adolescents With First-Episode Major Depressive Disorder].

Objective: To investigate the changes in serum inflammatory cytokines and the predictive factors for the efficacy of sertraline following medication therapy in adolescents with first-episode major depressive disorder (MDD). Methods: A total of 61 adolescent patients with first-episode drug-naïve MDD were enrolled for the MDD group and 55 healthy adolescents were enrolled for the healthy control (HC) group. Sertraline tablets were administered to the MDD group for 8 weeks after enrollment, while no medication was given to the HC group. In the MDD group, blood samples were collected to measure the cytokine levels and clinical data, including scores for the 17-item Hamilton Depression Scale (HAMD-17) and the Connor-Davidson Resilience Scale (CD-RISC), were assessed at baseline and at the end of the 8-week medication, whereas in the HC group, blood samples and clinical data were collected only at baseline. The correlation between the levels of serum inflammatory cytokines and depression severity in the MDD group was analyzed and stepwise linear regression of HAMD-17 in the MDD group was performed to find serologic indicators that could be used to predict the efficacy of sertraline. Results: At baseline, the levels of interleukin (IL)-1ß and IL-6 in the MDD group were significantly higher than those in the HC group (all P<0.0001), while the tumor necrosis factor (TNF)-α level in the MDD group was significantly lower than that in the HC group ( P=0.006). After 8 weeks of medication treatment, the MDD group showed decreased levels of IL-1ß and IL-6 and increased level of TNF-α compared to the pre-treatment levels. In addition, the HAMD-17 score, CD-RISC total score, and scores for perceived competence, trust and tolerance, and control, three factors of CD-RISC, all improved after treatment. There was no significant difference in serum cytokine levels at baseline between the subgroup showing response to the treatment and the non-responding subgroup. There was a weak correlation between IL-6 levels before and after treatment and CD-RISC scores and the scores for the trust and tolerance factor of CD-RISC before and after treatment. The baseline IL-1ß and TNF-α levels did not show significant effect on posttreatment HAMD-17 scores. Conclusions: Serum cytokine levels of adolescents with first-episode MDD differ significantly from those of healthy adolescents. Although IL-6 was found to be correlated with depression severity, there was not enough support for it to be used as a predictor of the antidepression efficacy of sertraline.

[Sequencing Analysis of miRNAs in Brain-Derived Exosomes of Adolescent Mice With Depression-Like Behaviors].

Objective: To explore the differential expression of microRNAs (miRNAs) in brain-derived exosomes (BDEs) of adolescent mice with depression-like behavior. Methods: The experimental group consisted of susceptible adolescent mice exposed to chronic social defeat stress (CSDS), and sucrose preference test (SPT) and open field test (OFT) were performed to evaluate their depression-like behaviors. BDEs were extracted by ultracentrifugation (UC). The morphology, particle size, and surface marker proteins of BDEs were examined by transmission electron microscopy, nano-flow cytometry and Western blot. The expression of miRNA in BDEs was evaluated by high-throughput RNA sequencing. GO enrichment analysis and KEGG pathway enrichment analysis were carried out based on bioinformatics. Results: The particle size of BDEs ranged between 50 to 100 nm and they displayed a typical disc-shaped vesicle structure. TSG101 and syntenin, the exosome-positive proteins, were detected. In the BDEs of mice with depression-like behaviors induced by CSDS, 13 miRNAs were significantly upregulated and 4 miRNAs were significantly downregulated. Go and KEGG analysis showed that differentially expressed miRNAs were significantly enriched in PI3K-Akt signaling pathway, axonal guidance, and hypoxic response. Conclusion: It was found in this study that exosomal miRNAs in brain tissue might be involved in such biological processes as insulin resistance, neuroplasticity, and hypoxic response, thereby regulating brain functions and causing depression-like behaviors.

Long-read sequencing revealed alterations of microbial relationship between tongue coating and gastric mucosa in patients with gastric intestinal metaplasia / 数字中医药（英文）

Objective@#To explore the microbial correlation between oral tongue coating (TC) and gastric mucosa (GM) in patients with gastric intestinal metaplasia (GIM).@*Methods@#The present study recruited 1360 volunteers for upper gastrointestinal cancer screening. The microbiota in TC and GM were profiled by long-read sequencing of full-length 16S rRNA gene. The microbial diversity, community structure, and linear discriminant analysis effect size (LEfSe) were analyzed by the software Visual Genomics. SparCC correlation analysis was used to construct the commensal network and the graphical display was conducted by R software.@*Results@#The population included 44 patients with precancerous GIM, and 28 matched controls with negative rapid urease test (RUT) and non-symptomatic chronic superficial gastritis (CSG). No significant difference in diversity was observed between GIM patients and controls in TC or GM microbiota (P > 0.05). Patients had a higher percentage of 41 – 60 co-occurring operational taxonomic units (OTUs) between TC and GM than controls (34.1% vs. 25.0%) (P < 0.05). The LEfSe showed that TC Prevotella melaninogenica and three gastric Helicobacter species (i.e., Helicobacter pylori, Helicobacter pylori XZ274, and Helicobacter pylori 83) were enriched in patients with GIM. Furthermore, GIM patients with positive RUT had a lower percentage of co-occurring OTUs over 20 (P < 0.05), and lower abundances of gastric Veillonella, Pseudonocardia, and Mesorhizobium than those with negative RUT (P < 0.05). The commensal network between TC and GM was more complex in GIM patients than in controls. GIM patients with positive RUT demonstrated more bacterial correlations between TC and GM than those with negative RUT. Finally, the serum ratio of PG-I/II was negatively correlated with three gastric Helicobacter species (Helicobacter pylori, Helicobacter pylori XZ274, and Helicobacter pylori 83) in patients with negative RUT (P < 0.05), and negatively correlated with two TC species (Fusobacterium nucleatum subsp. nucleatum and Campylobacter showae) in patients with positive RUT (P < 0.05).@*Conclusion@#The development of GIM potentiated the commensal network between oral TC and GM, providing microbial evidence of the correlation between TC and the stomach.

Regulation of Gamma-Aminobutyric Acid Transaminase Expression and Its Clinical Significance in Hepatocellular Carcinoma.

Background: Gamma-aminobutyric acid transaminase (ABAT) catalyzes the conversion of gamma-aminobutyric acid (GABA) into succinic semialdehyde. Although some evidence supports a key role of ABAT in the progression of hepatocellular carcinoma (HCC), no systematic analysis is available. Thus, this study aimed to investigate the possible mechanisms related to low ABAT expression and the prognostic value and potential functions of ABAT in HCC. Methods: We obtained relevant datasets from the Encyclopedia of RNA Interactomes, MethSurv, cBioPortal, TISIDB and The Cancer Genome Atlas and used bioinformatic methods to analyze DNA methylation, copy number variation, gene mutation, and upstream microRNAs (miRNAs) of ABAT, exploring the potential relationship between ABAT expression and the prognosis, glycolysis, and immune infiltration in HCC. Results: The results indicated that ABAT expression was lower in HCC tumor tissues than in normal tissues or adjacent tissues. Low ABAT expression was related to patient age, T stage classification, pathologic stage, histological grade, and alpha-fetoprotein level of HCC. Kaplan-Meier survival analyses indicated that low ABAT expression was correlated with poor HCC prognosis. ABAT was also verified as an independent risk factor in HCC via Cox multivariate analysis. Gene set enrichment analysis showed enrichment in various signaling pathways. Furthermore, DNA methylation, copy number variation, and gene mutation potentially induced low ABAT expression; miR-135a-5p was a potential upstream miRNA of ABAT. Additionally, ABAT expression was associated with glycolysis-related genes, infiltrated immune cells, immunoinhibitors, and immunostimulators in HCC. Conclusions: Our study reveals that deficient ABAT expression is correlated with disease progression and poor prognosis in HCC because of its role in tumorigenesis and tumor immunity.

Serum extracellular vesicle microRNA dysregulation and childhood trauma in adolescents with major depressive disorder.

Major depressive disorder (MDD) seriously endangers adolescent mental and physical health. Extracellular vesicles (EVs) are mediators of cellular communication and are involved in many physiological brain processes. Although EV miRNAshave been implicated in adults with major psychiatric disorders, investigation into their effects in adolescent MDDremains scarce. In discovery set, we conducted a genome-wide miRNA sequencing of serum EVs from 9 untreated adolescents with MDD and 8 matched healthy controls (HCs), identifying 32 differentially expressed miRNAs (18 upregulated and 14 downregulated). In the validation set, 8 differentially expressed and highly enriched miRNAs were verified in independent samples using RT-PCR, with 4 (miR-450a-2-3p, miR-3691-5p, miR-556-3p, and miR-2115-3p) of the 8 miRNAs found to be significantly elevated in 34 untreated adolescents with MDD compared with 38 HCs and consistent with the sequencing results. After the Bonferroni correction, we found that three miRNAs (miR-450a-2-3p, miR-556-3p, and miR-2115-3p) were still significantly different. Among them, miR-450a-2-3p showed the most markeddifferential expression and was able to diagnose disease with 67.6% sensitivity and 84.2% specificity. Furthermore, miR-450a-2-3p partially mediated the associations between total childhood trauma, emotional abuse, and physical neglect and adolescent MDD. We also found that the combination of miR-450a-2-3p and emotional abuse could effectively diagnose MDD in adolescents with 82.4% sensitivity and 81.6% specificity. Our data demonstrate the association of serum EV miRNA dysregulation with MDD pathophysiology and, furthermore, show that miRNAs may mediate the relationship between early stress and MDD susceptibility. We also provide a valid integrated model for the diagnosis of adolescent MDD.

Omicron variant of SARS-COV-2 gains new mutations in New Zealand and Hong Kong

Disclaimer statementThe authors have withdrawn this manuscript because an issue was raised about the SARS- COV-2 genome sequence data used in the study. Therefore, the authors do not wish this work to be cited as reference for the project. If you have any questions, please contact the corresponding author.

ISOC1 is a novel potential tumor suppressor in hepatocellular carcinoma.

Isochorismatase domain-containing 1 (ISOC1) plays a carcinogenic role in various tumors. However, its expression and role in hepatocellular carcinoma (HCC) have not been elucidated. This is the first study to investigate the involvement of ISOC1 in HCC growth and migration. ISOC1 expression was analyzed using public databases and clinical samples, and clinical specimens were analyzed by real-time quantitative polymerase chain reaction, western blotting, and immunohistochemistry. ISOC1 was also overexpressed in two HCC cell lines (Huh7 and HepG2) to explore how ISOC1 affects HCC cells. Finally, a nude mouse xenograft tumor model was used to investigate the role of ISOC1 in HCC cell tumorigenicity. ISOC1 was downregulated in HCC tissues compared to that in matched paracancerous tissues, and low ISOC1 expression was associated with a poor prognosis. The proliferation and single-cell colony-forming ability of the ISOC1-overexpressing cell lines Huh7 and HepG2 were significantly inhibited. Moreover, ISOC1 overexpression suppressed the migration and invasion abilities of HCC cells in vitro, and ISOC1 upregulation hindered tumor growth in the xenograft tumor model in vivo. Therefore, ISOC1 is a potential HCC suppressor protein.

Delta subvariants of SARS-COV-2 in Israel, Qatar and Bahrain: Optimal vaccination as an effective strategy to block viral evolution and control the pandemic

{delta} variant has rapidly become the predominant pandemic driver and yielded four subvariants ({delta}1, {delta}2, {delta}3 and {delta}4). Among them, {delta}1 has been mainly responsible for the latest COVID-19 waves in India, Southeast Asia, Europe and the USA. A relevant question is how {delta} subvariants may have driven the pandemic in the rest of the world. In both Israel and Qatar, mRNA-based vaccination has been rolled out competitively, but the outcomes are quite different in terms of controlling the recent waves resulting from {delta} variant. This raises the question whether {delta} subvariants have acted differently in Israel and Qatar. In both countries, {delta} variant was first identified in April 2021 and {delta}1 subvariant constituted [~]50% {delta} genomes from April to May 2021. But the situation started to diverge in June 2021: In Israel, {delta}1 variant was encoded by 92.0% {delta} genomes, whereas this fraction was only 43.9% in Qatar. Moreover, a {delta}1 sublineage encoding spike T791I was identified in Israel but not Qatar. This sublineage accounted for 31.8% {delta} genomes sequenced in June 2021 and declined to 13.3% in October 2021. In August 2021, {delta}1 also became dominant in Qatar and a major sublineage encoding spike D1259H emerged. This sublineage has evolved further and acquired additional spike substitutions, including K97E, S255F, I693S, I712S, I1104L, E1258D and/or V1177I, in Qatar and other countries, such as Czech Republic, France and Mexico. Monthly distribution of the above sublineages suggests that the one from Qatar is much more of concern than that from Israel. Different from what was in Israel and Qatar, {delta}2 subvariant has also been important in Bahrain, whereas a {delta}2 sublineage encoding spike V1264L and A1736V of NSP3 was dominant in June 2021, but was gradually taken over by {delta}1 subvariant. These results suggest that {delta}1 and {delta}2 subvariants continue their evolution in different countries. The recent successful pandemic control in Israel, Qatar and Bahrain supports that {delta}1 and {delta}2 subvariants are still sensitive to timed vaccination, thereby urging the use of optimal immunity as a strategy to block SARS-COV-2 evolution and control the pandemic.

SARS-COV-2 δ variant drives the pandemic in India and Europe via two subvariants

SARS-COV-2 evolution generates different variants and drives the pandemic. As the current main driver, {delta} variant bears little resemblance to the other three variants of concern, raising the question what features future variants of concern may possess. To address this important question, I compared different variant genomes and specifically analyzed {delta} genomes in the GISAID database for potential clues. The analysis revealed that {delta} genomes identified in India by April 2021 form four different groups (referred to as {delta}1, {delta}2, {delta}3 and {delta}4) with signature spike, nucleocapsid and NSP3 substitutions defining each group. Since May 2021, {delta}1 has gradually overtaken all other subvariants and become the dominant pandemic driver, whereas {delta}2 has played a less prominent role and the remaining two ({delta}3 and {delta}4) are insignificant. This group composition and variant transition are also apparent across Europe. In the United Kingdom, {delta}1 has quickly become predominant and is the sole pandemic driver underlying the current wave of COVID-19 cases. Alarmingly, {delta}1 subvariant has evolved further in the country and yielded a sublineage encoding spike V36F, A222V and V1264L. These substitutions may make the sublineage more virulent than {delta}1 itself. In the rest of Europe, {delta}1 is also the main pandemic driver, but {delta}2 still plays a role. In many European countries, there is a {delta}1 sublineage encoding spike T29A, T250I and Q613H. This sublineage originated from Morocco and has been a key pandemic driver there. Therefore, {delta} variant drives the pandemic in India and across Europe mainly through {delta}1 and {delta}2, with the former acquiring additional substitutions and yielding sublineages with the potential to drive the pandemic further. These results suggest a continuously branching model by which {delta} variant evolves and generates more virulent subvariants.

SARS-COV-2 γ variant acquires spike P681H or P681R for improved viral fitness

Severe acute respiratory syndrome coronavirus 2 (SARS-COV-2) evolves and generates different variants through a continuously branching model. Four variants of concern have been the major pandemic drivers around the world. One important question is how they may evolve and generate subvariants, some of which may be even more virulent and drive the pandemic further. While investigating how {gamma} (or P.1) variant has been evolving, I noticed the spike substitution P681H in a group of genomes encoding a new subvariant, which has been designated P.1.7. This subvariant has become the dominant P.1 sublineage in Brazil, Italy, Spain and Peru, supporting that P681H confers evolutionary advantage to P.1.7. In Brazil and Peru, P.1.7 was still responsible for ~30% and ~40% cases, respectively, in August 2021. However, it has been competed out by {delta}1 (a {delta} subvariant) in both countries, Italy and Spain, suggesting that P.1.7 is not as virulent as {delta}1. In addition, 160 P.1 genomes possess a related substitution, P681R, and 120 of them encode a new subvariant, designated P.1.8. This P.1 subvariant carries two additional spike substitutions, T470N and C1235F, located at the receptor-binding pocket and cytoplasmic tail of spike protein, respectively. More P.1.8 genomes have been identified than P.1 genomes that encode P681R but not T470N and C1235F, suggesting that these two substitutions improve virulence of P.1.8 subvariant. Some P.1 genomes carry other substitutions (such as N679K, V687L and C1250F) that affect the furin cleavage site or cytoplasmic tail of spike protein. Thus, to improve viral fitness and expand its evolutionary cage, {gamma} variant acquires mutations to finetune the furin cleavage site and cytoplasmic tail of spike protein.

SARS-COV-2 C.1.2 variant is highly mutated but may possess reduced affinity for ACE2 receptor

SARS-COV-2 evolution generates different variants and drives the pandemic. As the current main driver, delta variant bears little resemblance to the other three variants of concern (alpha, beta and gamma), raising the question what features the future variants of concern may possess. To address this important question, I searched through the GISAID database for potential clues. While investigating how beta variant has been evolving in South Africa, I noticed a small group of genomes mainly classified as C.1.2 variant, with one-year old boy identified in March 2021 being the index case. Over 80% patients are younger than 60. At the average, there are 46-47 mutations per genome, making this variant one of the most mutated lineages identified. A signature substitution is spike Y449H. Like beta and gamma variants, C.1.2 possesses E484K and N501Y. The genomes are heterogenous and encode different subvariants. Like alpha variant, one such subvariant encodes the spike substitution P681H at the furin cleavage site. In a related genome, this substitution is replaced by P681R, which is present in delta variant. In addition, similar to this variant of concern, three C.1.2 subvariants also encode T478K. Mechanistically, spike Y449 recognizes two key residues of the cell-entry receptor ACE2 and Y449H is known to impair the binding to ACE2 receptor, so C.1.2 variant may show reduced affinity for this receptor. If so, this variant needs other mutations to compensate for such deficiency. These results raise the question whether C.1.2 variant is as virulent as suggested by its unexpected high number of mutations.

δ1 variant of SARS-COV-2 acquires spike V1176F and yields a highly mutated subvariant in Europe

Genomic surveillance of SARS-COV-2 has revealed that in addition to many variants of interests, this virus has yielded four variants of concern, , {beta}, {gamma} and {delta}, as designated by the World Health Organization. {delta} variant has recently become the predominant pandemic driver around the world and yielded four different subvariants ({delta}1, {delta}2, {delta}3 and {delta}4). Among them, {delta}1 has emerged as the key subvariant that drives the pandemic in India, Europe and the USA. A relevant question is whether {delta}1 subvariant continues to evolve and acquires additional mutations. Related to this, this subvariant has acquired spike V1176F, a signature substitution of {gamma} variant, and yielded a new sublineage, {delta}1F. The substitution alters heptad repeat 2 of spike protein and is expected to improve interaction with heptad repeat 1 and enhance virus entry. Moreover, there are {delta}1F sublineages encoding spike N501Y, A783S, Q836E and V1264L. While N501Y is a signature substitution shared by , {beta} and {gamma} variants, V1264L is a key substitution in a {delta}1 sublineage that is a major pandemic driver in Southeast Asia. The Q836E-encoding lineage carries an average of 50 mutations per genome, making it the most mutated variant identified so far. Similar to {delta}1 subvariant, {delta}2 subvariant has also acquired spike V1176F and yielded new sublineages. Together, these results suggest that V1176F is a recurrent spike substitution that is frequently acquired by SARS-COV-2 variants to improve viral fitness. It is thus important to track the evolutionary trajectory of related variants for considering and instituting the most effective public health measures.

Simultaneously Enhanced Thermal Conductivity and Breakdown Performance of Micro/Nano-BN Co-Doped Epoxy Composites.

Micro/nano- BN co-doped epoxy composites were prepared and their thermal conductivity, breakdown strength at power frequency and voltage endurance time under high frequency bipolar square wave voltage were investigated. The thermal conductivity and breakdown performance were enhanced simultaneously in the composite with a loading concentration of 20 wt% BN at a micro/nano proportion of 95/5. The breakdown strength of 132 kV/mm at power frequency, the thermal conductivity of 0.81 W·m-1·K-1 and voltage endurance time of 166 s were obtained in the composites, which were approximately 28%, 286% and 349% higher than that of pristine epoxy resin. It is proposed that thermal conductive pathways are mainly constructed by micro-BN, leading to improved thermal conductivity and voltage endurance time. A model was introduced to illustrate the enhancement of the breakdown strength. The epoxy composites with high thermal conductivity and excellent breakdown performance could be feasible for insulating materials in high-frequency devices.