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Summary: Pseudomonas aeruginosa utilizes a type III secretion system (T3SS) to directly inject effector proteins into host cells, leading to severe acute infections. Here, we present a protocol for detecting the T3SS-mediated cytotoxicity of P. aeruginosa using the A549 cell line. We describe the steps for the preparation of the A549 cell line and P. aeruginosa strains, cell seeding, bacterial culture, infection, and cytotoxicity assay. Additionally, we provide detailed procedures for data analysis.For complete details on the use and execution of this protocol, please refer to Huang et al.1 : Publisher’s note: Undertaking any experimental protocol requires adherence to local institutional guidelines for laboratory safety and ethics.

The department of critical care medicine, the clinical base of critical care medicine, is the centralized management unit for the treatment of critical patients. Medicine and nursing are independent disciplines, but both can be fully utilized from different perspectives when dealing with critically ill patients. With the development of critical care medicine understanding and technology, the concept of doctor-nurse integration construction in the department of critical care medicine has emerged. Doctor-nurse integration construction in the department of critical care medicine needs to take severe diseases as the core and academic development as the orientation. Clinical practice should be carried out through medical cooperation, based on critical cognition and unified thinking mode.

Summary: Quorum sensing (QS) is a cell-to-cell communication mechanism mediated by small diffusible signaling molecules. Previous studies showed that RpfR controls Burkholderia cenocepacia virulence as a cis-2-dodecenoic acid (BDSF) QS signal receptor. Here, we report that the fatty acyl-CoA ligase DsfR (BCAM2136), which efficiently catalyzes in vitro synthesis of lauryl-CoA and oleoyl-CoA from lauric acid and oleic acid, respectively, acts as a global transcriptional regulator to control B. cenocepacia virulence by sensing BDSF. We show that BDSF binds to DsfR with high affinity and enhances the binding of DsfR to the promoter DNA regions of target genes. Furthermore, we demonstrate that the homolog of DsfR in B. lata, RS02960, binds to the target gene promoter, and perception of BDSF enhances the binding activity of RS02960. Together, these results provide insights into the evolved unusual functions of DsfR that control bacterial virulence as a response regulator of QS signal.

Abstract Previous studies have demonstrated that bis-(3',5')-cyclic diguanosine monophosphate (bis-3',5'-c-di-GMP) is a ubiquitous second messenger employed by bacteria. Here, we report that 2',3'-cyclic guanosine monophosphate (2',3'-cGMP) controls the important biological functions, quorum sensing (QS) signaling systems and virulence in Ralstonia solanacearum through the transcriptional regulator RSp0980. This signal specifically binds to RSp0980 with high affinity and thus abolishes the interaction between RSp0980 and the promoters of target genes. In-frame deletion of RSp0334, which contains an evolved GGDEF domain with a LLARLGGDQF motif required to catalyze 2',3'-cGMP to (2',5')(3',5')-cyclic diguanosine monophosphate (2',3'-c-di-GMP), altered the abovementioned important phenotypes through increasing the intracellular 2',3'-cGMP levels. Furthermore, we found that 2',3'-cGMP, its receptor and the evolved GGDEF domain with a LLARLGGDEF motif also exist in the human pathogen Salmonella typhimurium. Together, our work provides insights into the unusual function of the GGDEF domain of RSp0334 and the special regulatory mechanism of 2',3'-cGMP signal in bacteria.

Abstract Virulence factor modulating (VFM) is a quorum sensing (QS) signal shared by and specific to Dickeya bacteria, regulating the production of plant cell wall degrading enzymes (PCWDEs) and virulence of Dickeya. High polarity and trace of VFM signal increase the difficulty of signal separation and structure identification, and thus limit the development of quorum quenching strategy to biocontrol bacterial soft rot diseases caused by Dickeya. In order to high‐throughput screen VFM quenching bacteria, a vfmE‐gfp biosensor VR2 (VFM Reporter) sensitive to VFM signal was first constructed. Subsequently, two bacterial strains with high quenching efficiency were screened out by fluorescence intensity measurement and identified as Pseudomonas chlororaphis L5 and Enterobacter asburiae L95 using multilocus sequence analysis (MLSA). L5 and L95 supernatants reduced the expression of vfm genes, and both strains also decreased the production of PCWDEs of D. zeae MS2 and significantly reduced the virulence of D. oryzae EC1 on rice seedlings, D. zeae MS2 on banana seedlings, D. dadantii 3937 on potato and D. fangzhongdai CL3 on taro. Findings in this study provide a method to high‐throughput screen VFM quenching bacteria and characterize novel functions of P. chlororaphis and E. asburiae in biocontrolling plant diseases through quenching VFM QS signal.

ABSTRACT Dickeya fangzhongdai is a devastating bacterial pathogen infecting a wide range of crops and ornamental plants worldwide. As a newly identified bacterial species in 2016, the regulatory mechanisms that govern its virulence are still a mystery. In this study, we explored the potential roles of polyamine-mediated cell-to-cell communication in regulation of D. fangzhongdai virulence. Null mutation of speA and speC in D. fangzhongdai strain ZXC1, which encodes polyamine biosynthesis through arginine and ornithine pathways, respectively, dramatically reduced bacterial motility, decreased production of plant cell wall degradation (PCWD) enzymes, and attenuated the bacterial virulence on taro and potato. We then tested the effect of various polyamine molecules in the restoration of the mutant phenotypes and showed that putrescine was the most potent signal in the regulation of virulence traits in strain ZXC1. In addition, we found that taro extract contained active signals to rescue putrescine-deficient phenotypes. High-performance liquid chromatography mass spectrometry analysis validated the speA was essential for production of putrescine in D. fangzhongdai ZXC1. We further showed that the putrescine transporters PotF and PlaP are required for putrescine-mediated cell-to-cell communication and virulence against taro and potato tubers. quantitative reverse transcription-PCR analysis demonstrated that putrescine influences the pathogenicity of D. fangzhongdai ZXC1 by regulating the expression of PCWD enzymes, bacterial chemotaxis, and flagellar-related genes. The findings from this study shed a new light for elucidating the pathogenic mechanisms of D. fangzhongdai and present useful clues for developing relevant disease control strategies. IMPORTANCE Dickeya fangzhongdai is a newly identified plant bacterial pathogen with a wide host range. A clear understanding of the cell-to-cell communication systems that modulate the bacterial virulence is of key importance for elucidating its pathogenic mechanisms and for disease control. In this study, we present evidence that putrescine molecules from the pathogen and host plants play an essential role in regulating the bacterial virulence. The significance of this study is in (i) demonstrating that putrescine signaling system regulates D. fangzhongdai virulence mainly through modulating the bacterial motility and production of PCWD enzymes, (ii) outlining the signaling and regulatory mechanisms with which putrescine signaling system modulates the above virulence traits, and (iii) validating that D. fangzhongdai could use both arginine and ornithine pathways to synthesize putrescine signals. To our knowledge, this is the first report to show that putrescine signaling system plays a key role in modulating the pathogenicity of D. fangzhongdai.

Abstract Background Envelope stress responses (ESRs) are critical for adaptive resistance of Gram-negative bacteria to envelope-targeting antimicrobial agents. However, ESRs are poorly defined in a large number of well-known plant and human pathogens. Dickeya oryzae can withstand a high level of self-produced envelope-targeting antimicrobial agents zeamines through a zeamine-stimulated RND efflux pump DesABC. Here, we unraveled the mechanism of D. oryzae response to zeamines and determined the distribution and function of this novel ESR in a variety of important plant and human pathogens. Results In this study, we documented that a two-component system regulator DzrR of D. oryzae EC1 mediates ESR in the presence of envelope-targeting antimicrobial agents. DzrR was found modulating bacterial response and resistance to zeamines through inducing the expression of RND efflux pump DesABC, which is likely independent on DzrR phosphorylation. In addition, DzrR could also mediate bacterial responses to structurally divergent envelope-targeting antimicrobial agents, including chlorhexidine and chlorpromazine. Significantly, the DzrR-mediated response was independent on the five canonical ESRs. We further presented evidence that the DzrR-mediated response is conserved in the bacterial species of Dickeya, Ralstonia, and Burkholderia, showing that a distantly located DzrR homolog is the previously undetermined regulator of RND-8 efflux pump for chlorhexidine resistance in B. cenocepacia. Conclusions Taken together, the findings from this study depict a new widely distributed Gram-negative ESR mechanism and present a valid target and useful clues to combat antimicrobial resistance.

ABSTRACT Pseudomonas aeruginosa has abundant signaling systems that exquisitely control its antibiotic resistance in response to different environmental cues. Understanding the regulation of antibiotic resistance will provide important implications for precise antimicrobial interventions. However, efficient genetic tools for functional gene characterizations are sometimes not available, particularly, in clinically isolated strains. Here, we established a type I-F CRISPRi (CSYi) system for programmable gene silencing. By incorporating anti-CRISPR proteins, this system was even applicable to bacterial hosts encoding a native type I-F CRISPR-Cas system. With the newly developed gene-silencing system, we revealed that the response regulator CzcR from the zinc (Zn2+)-responsive two-component system CzcS/CzcR is a repressor of efflux pumps MexAB-OprM and MexGHI-OpmD, which inhibits the expression of both operons by directly interacting with their promoters. Repression of MexAB-OprM consequently increases the susceptibility of P. aeruginosa to multiple antibiotics such as levofloxacin and amikacin. Together, this study provided a simple approach to study gene functions, which enabled us to unveil the novel role of CzcR in modulating efflux pump genes and multidrug resistance in P. aeruginosa. IMPORTANCE P. aeruginosa is a ubiquitous opportunistic pathogen frequently causing chronic infections. In addition to being an important model organism for antibiotic-resistant research, this species is also important for understanding and exploiting CRISPR-Cas systems. In this study, we established a gene-silencing system based on the most abundant type I-F CRISPR-Cas system in this species, which can be readily employed to achieve targeted gene repression in multiple bacterial species. Using this gene-silencing system, the physiological role of Zn2+ and its responsive regulator CzcR in modulating multidrug resistance was unveiled with great convenience. This study not only displayed a new framework to expand the abundant CRISPR-Cas and anti-CRISPR systems for functional gene characterizations but also provided new insights into the regulation of multidrug resistance in P. aeruginosa and important clues for precise anti-pseudomonal therapies.

Aiming at the problem of fatigue life prediction of aluminum alloy wheel hub, a fatigue life prediction model considering damage accumulation is proposed and tested. The Finite Element Models of a wheel hub under bending fatigue test and radial fatigue test are established, and the main failure positions are studied by simulation analysis. The S-N curves of material and part are established by using the nominal stress method, and the average stress of the asymmetric cyclic load borne by the wheel hub is corrected by using the Morrow line. Considering the rotation process of the wheel hub, a theoretical model for predicting the fatigue life is constructed by using the linear cumulative damage theory. Taking an aluminum alloy wheel hub as an example, the life calculated by the theoretical model is 448.2 thousands revolutions. Compared with the fatigue life of 473.3 thousands revolutions given by the bending fatigue test, the error is about 5.6%, which verifies the effectiveness of the fatigue life prediction theoretical model.

The morphological characteristic of Dendrobium moschatum (Buch.-Ham.) Sw. 1805 is very distinctive among Dendrobium Sw. 1799, and it has high medicinal and ornamental values. Here, we reported the first complete chloroplast genome of D. moschatum. The complete genome of D. moschatum was 159,701 bp in length with 130 genes, including 38 tRNA, 8 rRNA, and 84 protein-coding genes. Phylogenetic analysis showed that D. moschatum was strongly allied with D. denneanum Kerr. 1933.

Water is the main component of wheat flour dough. Its content, distribution, presence state, and state of existence moisture have an important impact on the processing characteristics, preservation and product quality stability of the flour dough. Wheat flour is composed of a variety of components such as protein, starch, fat, pentosan, minerals and etc. Wheat flour is mixed with water to form a dough, in which complex physicochemical changes occur. The composition and physico-chemical properties of the various components in the dough have an important influence. Therefore, understanding the changes of different components in the process of dough mixing with water is of great significance for the quality control and quality improvement of products. In this review, the research results in related fields in recent years were classified and summarized, the interaction mechanism between different components in wheat flour and with water molecules was systematically analyzed, the water absorption and water holding characteristics of different components of wheat flour were discussed, and the effects of different components of wheat flour on water distribution and migration were analyzed. This paper concluded the key ingredients that determine the moisture migration and product quality of dough, such as protein, starch, damaged starch and pentosan etc., in order to further guide the production of wheat flour products.

Using stannous octanoate as catalyst and 1,4-butanediol as initiator, ring-opening polymerization of ε-caprolactone and DL-lactide was carried out to prepare ε-caprolactone and DL-lactide copolymer with hydroxyl groups at both ends (PCDLA-OH prepolymer), and then L-lactide ring-opening polymerization was initiated by PCDLA-OH prepolymer to prepare triblock copolymer with poly L-lactide segments at both ends and ε-caprolactone and DL-lactide copolymer in the middle (PLLA-b-PCDLA-b-PLLA) was prepared, and the structure and properties of the block copolymer were tested. The results showed that the larger the amount of DL-lactide in PCDLA-OH prepolymer, the prepolymer gradually changed from partial crystallization to amorphous polymer, and the glass transition tempe-rature gradually increased. When the mole ratio of DL-lactide to ε-caprolactone was 3/10 and the mass ratio of PCDLA-OH prepolymer to L-lactide was 1/5, the elongation at break and tensile strength of the prepared PLLA-b-PCDLA-b-PLLA were 204% and 4.77 MPa.

Bacterial wilt caused by Ralstonia solanacearum ranks the second top important bacterial plant disease worldwide. It is also the most important bacterial disease threatening the healthy development of Casuarina equisetifolia protection forest. 3-hydroxypalmitic acid methyl ester (3-OH PAME) functions as an important quorum sensing (QS) signal regulating the expression of virulence genes in R. solanacearum, and has been regarded as an ideal target for disease prevention and control. To screen native microorganisms capable of degrading 3-OH PAME, samples of C. equisetifolia branches and forest soil were collected and cultured in the medium containing 3-OH PAME as the sole carbon source. Bacteria with over 85% degradation rates of 3-OH PAME after 7-day incubation were further separated and purified. As a result, strain Q1-7 isolated from forest soil and strain Q4-3 isolated from C. equisetifolia branches were obtained and identified as Pseudomonas novel species Pseudomonas forestsoilum sp. nov. and P. tohonis, respectively, according to whole genome sequencing results. The degradation efficiencies of 3-OH PAME of strains Q1-7 and Q4-3 were 95.80% and 100.00% at 48 h, respectively. Both strains showed high esterase activities and inhibited R. solanacearum exopolysaccharide (EPS) and cellulase production. Application of strains Q1-7 and Q4-3 effectively protects C. equisetifolia, peanut and tomato plants from infection by R. solanacearum. Findings in this study provide potential resources for the prevention and control of bacterial wilt caused by R. solanacearum, as well as valuable materials for the identification of downstream quenching genes and the research and development of quenching enzymes for disease control.

Huanglongbing (HLB) is one of the most devastating diseases of citrus worldwide. The phloem-restricted bacterium Candidatus Liberibacter asiaticus (CLas) is considered to be the main pathogen responsible for HLB. There is currently no effective practical strategy for the control of HLB. Our understanding of how pathogens cause HLB is limited because CLas has not been artificially cultured. In this study, 15 potential virulence factors were predicted from the proteome of CLas through DeepVF and PHI-base searches. One among them, FlgI, was found to inhibit yeast growth when expressed in Saccharomyces cerevisiae. The expression of the signal peptide of FlgI fused with PhoA in Escherichia coli resulted in the discovery that FlgI was a novel Sec-dependent secretory protein. We further found that the carboxyl-terminal HA-tagged FlgI was secreted via outer membrane vesicles in Sinorhizobium meliloti. Fluoresence localization of transient expression FlgI-GFP in Nicotiana benthamiana revealed that FlgI is mainly localized in the cytoplasm, cell periphery, and nuclear periphery of tobacco cells. In addition, our experimental results suggest that FlgI has a strong ability to induce callose deposition and cell necrosis in N. benthamiana. Finally, by screening a large library of compounds in a high-throughput format, we found that cyclosporin A restored the growth of FlgI-expressing yeast. These results confirm that FlgI is a novel Sec-dependent effector, enriching our understanding of CLas pathogenicity and helping to develop new and more effective strategies to manage HLB.

The Hidden Quantum Markov Model (HQMM) has significant potential for analyzing time-series data and studying stochastic processes in the quantum domain as an upgrading option with potential advantages over classical Markov models. In this paper, we introduced the split HQMM (SHQMM) for implementing the hidden quantum Markov process, utilizing the conditional master equation with a fine balance condition to demonstrate the interconnections among the internal states of the quantum system. The experimental results suggest that our model outperforms previous models in terms of scope of applications and robustness. Additionally, we establish a new learning algorithm to solve parameters in HQMM by relating the quantum conditional master equation to the HQMM. Finally, our study provides clear evidence that the quantum transport system can be considered a physical representation of HQMM. The SHQMM with accompanying algorithms present a novel method to analyze quantum systems and time series grounded in physical implementation.

The A-type granites with highly positive εNd(t) values in the West Junggar, Central Asian Orogenic Belt (CAOB), have long been perceived as a group formed under the same tectonic and geodynamic setting, magmatic sourceq and petrogenetic model. Geological evidence shows that these granites occurred at two different tectonic units related to the southeastern subduction of Junggar oceanic plate: the Hongshan and Karamay granites emplaced in the southeast of West Junggar in the Baogutu continental arc; whereas the Akebasitao and Miaoergou granites formed in the accretionary prism. Here the authors present new bulk-rock geochemistry and Sr-Nd isotopes, zircon U-Pb ages and Hf-O isotopes data on these granites. The granites in the Baogutu continental arc and accretionary prism contain similar zircon εHf(t) values (+10.9 to +16.2) and bulk-rock geochemical characteristics (high SiO2 and K2O contents, enriched LILEs (except Sr), depleted Sr, Ta and Ti, and negative anomalies in Ce and Eu). The Hongshan and Karamay granites in the Baogutu continental arc have older zircon U-Pb ages (315–305 Ma) and moderate 18O enrichments (δ18Ozircon=+6.41‰–+7.96‰); whereas the Akebasitao and Miaoergou granites in the accretionary prism have younger zircon U-Pb ages (305–301 Ma) with higher 18O enrichments (δ18Ozircon=+8.72‰–+9.89‰). The authors deduce that the elevated 18O enrichments of the Akebasitao and Miaoergou granites were probably inherited from low-temperature altered oceanic crusts. The Akebasitao and Miaoergou granites were originated from partial melting of low-temperature altered oceanic crusts with juvenile oceanic sediments below the accretionary prism. The Hongshan and Karamay granites were mainly derived from partial melting of basaltic juvenile lower crust with mixtures of potentially chemical weathered ancient crustal residues and mantle basaltic melt (induced by hot intruding mantle basaltic magma at the bottom of the Baogutu continental arc). On the other hand, the Miaoergou charnockite might be sourced from a deeper partial melting reservoir under the accretionary prism, consisting of the low-temperature altered oceanic crust, juvenile oceanic sediments, and mantle basaltic melt. These granites could be related to the asthenosphere’s counterflow and upwelling, caused by the break-off and delamination of the subducted oceanic plate beneath the accretionary prism Baogutu continental arc in a post-collisional tectonic setting.©2022 China Geology Editorial Office.

The GacS-GacA type two-component system (TCS) positively regulates pathogenicity-related phenotypes in many plant pathogens. In addition, Dickeya oryzae EC1, the causative agent of soft rot disease, produces antibiotic‐like toxins called zeamines as one of the major virulence factors that inhibit the germination of rice seeds. The present study identified a GacS-GacA type TCS, named TzpS-TzpA, that positively controls the virulence of EC1, mainly by regulating production of the toxin zeamines. RNA-seq analysis of strain EC1 and its tzpA mutant showed that the TCS regulated a wide range of virulence genes, especially those encoding zeamines. Protein-protein interaction was detected between TzpS and TzpA through the bacterial two-hybrid system and pull-down assay. In trans expression of tzpA failed to rescue the defective phenotypes in both the ΔtzpS and ΔtzpSΔtzpA mutants. Furthermore, TzpA controls target gene expression by direct binding to DNA promoters that contain a Gac-box motif, including a regulatory RNA rsmB and the vfm quorum-sensing system regulator vfmE. These findings therefore suggested that the EC1 TzpS-TzpA TCS system mediates the pathogenicity of Dickeya oryzae EC1 mainly by regulating the production of zeamines.[Graphic: see text] Copyright © 2022 The Author(s). This is an open access article distributed under the CC BY-NC-ND 4.0 International license.

Gantries and beams, as the main load-bearing structures of heavy equipment, usually belong to the box structure consisting of outer walls and inner stiffened plates. The structure of the stiffener layout is bulky due to empirical design, leading to higher material consumption and impacting mechanical performance. There are challenges in effectively identifying load-transferred paths within 3D box structures through direct topological optimization. A method for optimizing the layout of internal stiffened plates of large box structures based on load paths is proposed in this paper. Initially, based on the load conditions acting on the structure, the 3D box structure is decomposed into 2D functional sections. Subsequently, the load paths on the functional cross-section are visualized according to the load path method. Finally, the stiffener layout of the ultimate optimized structure is designed according to the effective load path distribution. Taking the gantry of a heavy-duty aluminum ingot composite processing unit as an example, the optimization results indicate that the maximum stress of the structure decreased by 14.9%, the maximum deformation reduced by 32.95%, and the overall weight decreased by 14.4%. This demonstrates that the approach proposed in this paper is practical and effective for optimizing stiffener layouts in large-box structures. [ABSTRACT FROM AUTHOR]

ABSTRACT Diffusible signal factor (DSF) represents a family of widely conserved quorum-sensing (QS) signals which regulate virulence factor production and pathogenicity in numerous Gram-negative bacterial pathogens. We recently reported the identification of a highly potent DSF-quenching bacterial isolate, Pseudomonas nitroreducens HS-18, which contains an operon with four DSF-inducible genes, digABCD, or digA–D, that are responsible for degradation of DSF signals. However, the regulatory mechanisms that govern the digA–D response to DSF induction have not yet been characterized. In this study, we identified a novel transcriptional regulator we designated RdmA (regulator of DSF metabolism) which negatively regulates the expression of digA–D and represses DSF degradation. In addition, we found that a gene cluster located adjacent to rdmA was also negatively regulated by RdmA and played a key role in DSF degradation; this cluster was hence named dmg (DSF metabolism genes). An electrophoretic mobility shift assay and genetic analysis showed that RdmA represses the transcriptional expression of the dmg genes in a direct manner. Further studies demonstrated that DSF acts as an antagonist and binds to RdmA, which abrogates RdmA binding to the target promoter and its suppression on transcriptional expression of the dmg genes. Taken together, the results from this study have unveiled a central regulator and a gene cluster associated with the autoinduction of DSF degradation in P. nitroreducens HS-18, and this will aid in the understanding of the genetic basis and regulatory mechanisms that govern the quorum-quenching activity of this potent biocontrol agent. IMPORTANCE DSF family quorum-sensing (QS) signals play important roles in regulation of bacterial physiology and virulence in a wide range of plant and human bacterial pathogens. Quorum quenching (QQ), which acts by either degrading QS signals or blocking QS communication, has proven to be a potent disease control strategy, but QQ mechanisms that target DSF family signals and associated regulatory mechanisms remain largely unknown. Recently, we identified four autoinduced DSF degradation genes (digABCD) in P. nitroreducens HS-18. By using a combination of transcriptome and genetic analysis, we identified a central regulator that plays a key role in autoinduction of dig expression, as well as a new gene cluster (dmgABCDEFGH) involved in DSF degradation. The significance of our study is in unveiling the autoinduction mechanism that governs DSF signal quorum quenching for the first time, to our knowledge, and in identification of new genes and enzymes responsible for DSF degradation. The findings from this study shed new light on our understanding of the DSF metabolism pathway and the regulatory mechanisms that modulate DSF quorum quenching and will provide useful clues for design and development of a new generation of highly potent QQ biocontrol agents against DSF-mediated bacterial infections.

With the increasing resistance exhibited by undesirable bacteria to traditional antibiotics, the need to discover alternative (or, at least, supplementary) treatments to combat chemically resistant bacteria is becoming urgent. Quorum sensing (QS) refers to a novel bacterial communication system for monitoring cell density and regulation of a network of gene expression that is mediated by a group of signaling molecules called autoinducers (AIs). QS-regulated multicellular behaviors include biofilm formation, horizontal gene transfer, and antibiotic synthesis, which are demonstrating increasing pathogenicity to plants and aquacultural animals as well as contamination of wastewater treatment devices. To inhibit QS-regulated microbial behaviors, the strategy of quorum quenching (QQ) has been developed. Different quorum quenchers interfere with QS through different mechanisms, such as competitively inhibiting AI perception (e.g., by QS inhibitors) and AI degradation (e.g., by QQ enzymes). In this review, we first introduce different signaling molecules, including diffusible signal factor (DSF) and acyl homoserine lactones (AHLs) for Gram-negative bacteria, AIPs for Gram-positive bacteria, and AI-2 for interspecies communication, thus demonstrating the mode of action of the QS system. We next exemplify the QQ mechanisms of various quorum quenchers, such as chemical QS inhibitors, and the physical/enzymatic degradation of QS signals. We devote special attention to AHL-degrading enzymes, which are categorized in detail according to their diverse catalytic mechanisms and enzymatic properties. In the final part, the applications and advantages of quorum quenchers (especially QQ enzymes and bacteria) are summarized in the context of agricultural/aquacultural pathogen biocontrol, membrane bioreactors for wastewater treatment, and the attenuation of human pathogenic bacteria. Taken together, we present the state-of-the-art in research considering QS and QQ, providing theoretical evidence and support for wider application of this promising environmentally friendly biocontrol strategy.

BackgroundIn the 21st century, the prevalence of tinnitus is increasing, impacting approximately one in five people. It is a very complicated condition that significantly affects quality of life. Despite the availability of hundreds of tinnitus treatment options, none are very successful. In light of this, there has been a steady increase in studies on tinnitus treatments in the recent past. To comprehend them better, this study used bibliometric approaches to analyze and summarize 21st century scientific research accomplishments in tinnitus treatment.MethodsThe Web of Science Core Collection (WoSCC) was searched for papers that had been published and related to the treatment of tinnitus. VOSviewer, CiteSpace, R, and Tableau software programs were used to conduct bibliometric studies. To evaluate and visualize the results.Results2,933 publications on tinnitus treatment were found in 74 countries. Between 2000 and 2021, publications increased steadily. Otolaryngology-Head & Neck Surgery had the highest impact factor, whereas Otology & Neurotology had the most magazines and the highest h, g, and m index. Langguth B was the most prolific author in terms of productivity during the past 21 years. Numerous eminent authors and organizations from multiple nations collaborated. With 626 papers, the United States of America (USA) contributed the most to this field, making them the leading contributor. Neuroplasticity, sound therapy, and cognitive behavioral therapy (CBT) have attracted the attention of researchers, leading to the development of innovative diagnostic and treatment strategies for tinnitus.ConclusionThis bibliometric study provides a comprehensive analysis of worldwide publications, cooperation, and research hotspots in tinnitus therapy, revealing the present status of research on this issue and guiding tinnitus treatment research in the coming years.

Seed germination and seedling development in nearly all orchid species rely on a symbiotic relationship with mycorrhizal fungi; however, this is not the case with all mycorrhizal fungi. This study aims to provide an understanding about the important role of mycorrhiza in seed germination and growth of Paphiopedilum barbigerum. Therefore, we isolated and identified endophytic fungi from the roots of wild P. barbigerum. The beneficial mycorrhizal fungi Epulorhiza sp. FQXY019 and Tulasnella calospora FQXY017 were screened by seed symbiotic germination tests and found to promote seed germination. However, only the seeds inoculated with FQXY019 progressed from the seed germination to rooting stage. This shows that mycorrhizal fungi and P. barbigerum have a specific relation at different growth phases. In addition, we selected FQXY019 and inoculated it into MS medium, B5 medium, OMA medium, and PDA medium. The results showed that FQXY019 co-cultured on PDA significantly promoted the increase in seedling fresh weight, leaf length, and root length (p

Pseudomonas aeruginosa, a major inhabitant of numerous environmental reservoirs, is a momentous opportunistic human pathogen associated with severe infections even death in the patients suffering from immune deficiencies or metabolic diseases. Type III secretion system (T3SS) employed by P. aeruginosa to inject effector proteins into host cells is one of the pivotal virulence factors pertaining to acute infections caused by this pathogen. Previous studies showed that P. aeruginosa T3SS is regulated by various environmental cues such as calcium concentration and the host signal spermidine. However, how T3SS is regulated and expressed particularly under the ever-changing environmental conditions remains largely elusive. In this study, we reported that a tRNA modification enzyme PA3980, designated as MiaB, positively regulated T3SS gene expression in P. aeruginosa and was essential for the induced cytotoxicity of human lung epithelial cells. Further genetic assays revealed that MiaB promoted T3SS gene expression by repressing the LadS-Gac/Rsm signaling pathway and through the T3SS master regulator ExsA. Interestingly, ladS, gacA, rsmY and rsmZ in the LadS-Gac/Rsm signaling pathway seemed potential targets under the independent regulation of MiaB. Moreover, expression of MiaB was found to be induced by the cAMP-dependent global regulator Vfr as well as the spermidine transporter-dependent signaling pathway and thereafter functioned to mediate their regulation on the T3SS gene expression. Together, these results revealed a novel regulatory mechanism for MiaB, with which it integrates different environmental cues to modulate T3SS gene expression in this important bacterial pathogen.

ABSTRACT Two-component system (TCS) plays a vital role in modulating target gene expression in response to the changing environments. Pseudomonas aeruginosa is a ubiquitous opportunistic pathogen that can survive under diverse stress conditions. The great adaptability of P. aeruginosa relies heavily on the abundant TCSs encoded by its genome. However, most TCSs in P. aeruginosa have not been well-characterized. CzcS/CzcR is a metal responsive TCS which displays multiple regulatory functions associated with metal hemostasis, quorum sensing activity and antibiotic resistance. In this study, we found that swimming motility of P. aeruginosa was completely abolished during zinc (Zn2+) stress when the czcR gene from the TCS CzcS/CzcR was deleted. Noticeably, CzcR was dispensable for swimming without the stress of Zn2+ excess. CzcR was shown to be activated by Zn2+ stress possibly through inducing its expression level and triggering its phosphorylation to positively regulate swimming which was abolished by Zn2+ stress in a CzcR-independent manner. Further TEM analyses and promoter activity examinations revealed that CzcR was required for the expression of genes involved in flagellar biosynthesis during Zn2+ stress. In vitro protein-DNA interaction assay showed that CzcR was capable of specifically recognizing and binding to the promoters of operons flgBCDE, flgFGHIJK, and PA1442/FliMNOPQR/flhB. Together, this study demonstrated a novel function of CzcR in regulating flagellar gene expression and motility in P. aeruginosa when the pathogen encounters Zn2+ stress conditions. IMPORTANCE The fitness of bacterial cells depends largely on their ability to sense and respond quickly to the changing environments. P. aeruginosa expresses a great number of signal sensing and transduction systems that enable the pathogen to grow and survive under diverse stress conditions and cause serious infections at different sites in many hosts. In addition to the previously characterized functions to regulate metal homeostasis, quorum sensing activity, and antibiotic resistance, here we report that CzcR is a novel regulator essential for flagellar gene expression and swimming motility in P. aeruginosa during Zn2+ stress. Since swimming motility is important for the virulence of P. aeruginosa, findings in this study might provide a new target for the treatment of P. aeruginosa infections with Zn2+-based antimicrobial agents in the future.