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Journal articles on the topic 'AgrC'

Author: Grafiati

Published: 6 September 2023

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1

Zhang, Linsheng, and Guangyong Ji. "Identification of a Staphylococcal AgrB Segment(s) Responsible for Group-Specific Processing of AgrD by Gene Swapping." Journal of Bacteriology 186, no. 20 (October 15, 2004): 6706–13. http://dx.doi.org/10.1128/jb.186.20.6706-6713.2004.

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ABSTRACT The four gene products of the accessory gene regulator (agr) P2 operon of Staphylococcus aureus assemble a quorum-sensing system: AgrA and AgrC resemble a two-component signal transduction system, and AgrB and AgrD are required to produce an autoinducing peptide. Upon activation, this quorum-sensing system positively regulates the transcription of the P2 operon as well as the P3 operon, whose transcript, RNAIII, regulates the expression of virulence genes. Four groups of S. aureus have been identified based on the agr sequences and the group-specific interaction between the autoinducing peptide and AgrC. AgrB is a transmembrane protein involved in the processing of AgrD propeptide, and its interaction with AgrD is also group specific. In this study, a series of chimeric AgrBs were constructed by swapping between group I and group II AgrBs, and these mutants were used to analyze the group-specific segment(s) in AgrB that was responsible for AgrD processing. Our results revealed that the first transmembrane α-helix and the extracellular loop 1 of group I AgrB were decisive in the specific processing of group I AgrD. In contrast, two hydrophilic segments of group II AgrB played a crucial role in the group-specific processing of group II AgrD. We also found that several chimeric AgrBs were capable of processing AgrD from both groups, suggesting that all AgrB homologues may utilize the same or a similar mechanism in the processing of AgrDs.

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2

Niyigaba, Jean, Jessica Ya Sun, Daiyan Peng, and Clemence Uwimbabazi. "Agriculture and Green Economy for Environmental Kuznets Curve Adoption in Developing Countries: Insights from Rwanda." Sustainability 12, no. 24 (December 11, 2020): 10381. http://dx.doi.org/10.3390/su122410381.

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Development and climate change are crucial global concerns with significant contrasts between developed and developing nations. Contrary to several developing countries, Rwanda opted for a green growth policy pathway while struggling with its economic emergence through the alternative green sectors, including agriculture. No research has yet been conducted on the choice’s performance on emission sequestration or the country’s income, allowing the formulation of strategies accordingly. The environmental Kuznets curve (EKC), mostly adopted by developed countries, is applied for the Rwandese scenario to verify its adoption in developing countries. The within and between effects of the agricultural sector (AGRc) and gross domestic products (GDPc) on CO2 emission (CO2) are examined with an Autoregressive Distributed Lag (ARDL) cointegration and coupling methods in January 2008−December 2018 period. Results confirm the short-run and long-run cointegration relationships of variables, where CO2-GDPc and CO2-AGRc are relatively decoupling and absolute decoupling, respectively. The EKC adoption to CO2-GDPc relationship, and the significant negative causality from GDPc and AGRc to CO2, are confirmed. The performance resulted from the country’s environment conservation policies, and Rwanda is a learning example as a developing country. However, the green economy through the agro-economy is at a low level and should be reinforced.

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Rieu, Aurélie, Stéphanie Weidmann, Dominique Garmyn, Pascal Piveteau, and Jean Guzzo. "agr System of Listeria monocytogenes EGD-e: Role in Adherence and Differential Expression Pattern." Applied and Environmental Microbiology 73, no. 19 (August 3, 2007): 6125–33. http://dx.doi.org/10.1128/aem.00608-07.

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ABSTRACT In this study, we investigated the agrBDCA operon in the pathogenic bacterium Listeria monocytogenes EGD-e. In-frame deletion of agrA and agrD resulted in an altered adherence and biofilm formation on abiotic surfaces, suggesting the involvement of the agr system of L. monocytogenes during the early stages of biofilm formation. Real-time PCR experiments indicated that the transcript levels of agrBDCA depended on the stage of biofilm development, since the levels were lower after the initial attachment period than during biofilm growth, whereas transcription during planktonic growth was not growth phase dependent. The mRNA quantification data also suggested that the agr system was autoregulated and pointed to a differential expression of the agr genes during sessile and planktonic growth. Although the reverse transcription-PCR experiments revealed that the four genes were transcribed as a single messenger, chemical half-life and 5′ RACE (rapid amplification of cDNA ends) experiments indicated that the full size transcript underwent cleavage followed by degradation of the agrC and agrA transcripts, which suggests a complex regulation of agr transcription.

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Lade, Harshad, Sung Hee Chung, Yeonhee Lee, Bajarang Vasant Kumbhar, Hwang-Soo Joo, Yun-Gon Kim, Yung-Hun Yang, and Jae-Seok Kim. "Thymol Reduces agr-Mediated Virulence Factor Phenol-Soluble Modulin Production in Staphylococcus aureus." BioMed Research International 2022 (May 9, 2022): 1–14. http://dx.doi.org/10.1155/2022/8221622.

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Staphylococcus aureus is a major human bacterial pathogen that carries a large number of virulence factors. Many virulence factors of S. aureus are regulated by the accessory gene regulator (agr) quorum-sensing system. Phenol-soluble modulins (PSMs) are one of the agr-mediated virulence determinants known to play a significant role in S. aureus pathogenesis. In the present study, the efficacy of thymol to inhibit PSM production including δ-toxin in S. aureus was explored. We employed liquid chromatography–mass spectrometry (LC–MS) to quantify the PSMsα1–PSMα4, PSMβ1 and PSMβ2, and δ-toxin production from culture supernatants. We found that thymol at 0.5 MIC (128 μg/mL) significantly reduced the PSMα and δ-toxin production in S. aureus WKZ-1, WKZ-2, LAC USA300, and ATCC29213. Downregulation in transcription by quantitative real-time (qRT) PCR analysis of response regulator agrA and receptor histidine kinase agrC upon 0.5 MIC thymol treatment affirmed the results of LC–MS quantification of PSMs. In silico molecular docking analysis demonstrated the binding affinity of thymol with receptors AgrA and AgrC. Transmission electron microscopy images revealed no ultrastructural alterations (cell wall and membrane) in thymol-treated WKZ-1 and WKZ-2 S. aureus strains. Here, we demonstrated that thymol reduces various PSM production in S. aureus clinical isolates and reference strains with mass spectrometry.

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5

McNamara, Peter J., and John J. Iandolo. "Genetic Instability of the Global Regulator agrExplains the Phenotype of the xpr Mutation inStaphylococcus aureus KSI9051." Journal of Bacteriology 180, no. 10 (May 15, 1998): 2609–15. http://dx.doi.org/10.1128/jb.180.10.2609-2615.1998.

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ABSTRACT Staphylococcus aureus KSI9051 has a complex mutation that was associated with the aberrant expression of cell surface and extracellular proteins (M. S. Smeltzer, M. E. Hart, and J. J. Iandolo, J. Bacteriol. 61:919–925, 1993). This mutation was named xpr, although no specific gene was identified. Here this mutation is referred to as Δ1058::Tn551. In this study, we show that in strain KSI9051, the Δ1058::Tn551 mutation occurred coincidentally with a frameshift in agrC that is expected to truncate the sensor component of the known staphylococcal global regulatory locus agr. Remarkably, pleiotropic mutations affecting cell surface and extracellular proteins are generated at frequencies approaching 50% upon the transduction of erythromycin resistance (Emr) encoded by Δ1058::Tn551 from S. aureus KSI905 back to its parental strain, S6C. Three independent isolates created in the manner of KSI9051 contained mutations within agrC. Each isolate had different mutations, suggesting that the transduction of Emr encoded by Δ1058::Tn551 affects the stability ofagrC in S6C. In similar experiments with strains from anS. aureus 8325 genetic background, a mutant AgrC phenotype could not be isolated, implying that strain S6 has aberrant genetic behavior. A comparison of the nucleotide sequences of AgrC from several strains revealed seven errors in the GenBank entry for agr(X52543 ); these data were confirmed with plasmid pRN6650, the original wild-type clone of agr.

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6

van Leeuwen, Willem, Wendy van Nieuwenhuizen, Christel Gijzen, Henri Verbrugh, and Alex van Belkum. "Population Studies of Methicillin-Resistant and -Sensitive Staphylococcus aureus Strains Reveal a Lack of Variability in the agrD Gene, Encoding a Staphylococcal Autoinducer Peptide." Journal of Bacteriology 182, no. 20 (October 15, 2000): 5721–29. http://dx.doi.org/10.1128/jb.182.20.5721-5729.2000.

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ABSTRACT The virulence of Staphylococcus aureus is controlled by the accessory gene regulator (agr) system, including an extracellular inducer encoded by agrD. Variableagr PCR restriction fragment length polymorphism (RFLP) patterns of unique S. aureus strains (n = 192) were determined for a region comprising agrD and parts of the neighboring agrC and agrB genes. Twelve unique RFLP patterns were identified among S. aureusstrains in general; these patterns were further specified by sequencing. All sequences could be catalogued in the three currentagr groups. A major proportion of the S. aureusstrains belong to agr group 1, whereas only 6% of the methicillin-susceptible S. aureus strains and 5% of the methicillin-resistant S. aureus strains belong toagr groups 2 and 3, respectively. The homology between groups varied from 75 to 80%, and within groups it varied from 96 to 100%. Different levels of sequence variability were observed in the different agr genes. agr-related bacterial interference among colonizing S. aureus strains in the noses of persistent and intermittent human carriers was studied.S. aureus strains belonging to different agr groups were encountered in the same individual. This may suggest that the activity of the agrD gene product does not define colonization dynamics, which is further substantiated by the rarity ofagr group 2 and 3 strains.

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7

Sung, Julia M. L., Peter D. Chantler, and David H. Lloyd. "Accessory Gene Regulator Locus of Staphylococcus intermedius." Infection and Immunity 74, no. 5 (May 2006): 2947–56. http://dx.doi.org/10.1128/iai.74.5.2947-2956.2006.

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ABSTRACT The accessory gene regulator (agr) locus, a candidate system for the regulation of the production of virulence factors in Staphylococcus intermedius, has been characterized. Using PCR-based genome walking, we have obtained the first complete sequence (3,436 bp) of the accessory gene regulator (agr) gene in this organism. Sequence analysis of the agr gene has identified five open reading frames (ORFs), agrB, agrD, agrC, agrA, and hld. The translated ORF contained amino acid motifs characteristic of the response regulator and histidine protein kinase signal transducer of the classic two-component regulatory system. Sequencing of the agrD PCR products amplified from DNA from 20 different isolates has facilitated detection of genetic variation in the putative autoinducing peptide (AIP) within the agr gene of S. intermedius, revealing the presence of at least three agr specificity groups within this species. Classification of the agr gene from S. intermedius was supported by phylogenetic analysis. Real-time PCR also revealed that the effector molecule of the agr system, RNAIII, was regulated in an autocrine manner in S. intermedius and demonstrated positive correlation with the temporal gene expression patterns of luk and entC. Transcription of RNAIII was also dependent on self secreted cues. Cyclic self and nonself peptides were synthesized on the basis of the novel AIPs produced by S. intermedius, which lack the cysteine necessary to form the thiolactone ring in analogous peptides from Staphylococcus aureus and Staphylococcus epidermidis. Experiments with these synthetic cyclic peptides indicated that self peptides led to up-regulation of RNAIII—findings in support of the assumption that activation of the agr gene is initiated by growth- and species-specific factors generated during bacterial growth.

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8

Xie, Qian, Mareike M. Wiedmann, Aishan Zhao, Ivelisse R. Pagan, Richard P. Novick, Hiroaki Suga, and Tom W. Muir. "Discovery of quorum quenchers targeting the membrane-embedded sensor domain of the Staphylococcus aureus receptor histidine kinase, AgrC." Chemical Communications 56, no. 76 (2020): 11223–26. http://dx.doi.org/10.1039/d0cc04873a.

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9

Wang, Lina, Chunshan Quan, Yongbin Xu, Xihui Li, Xiaojing Qu, and Shengdi Fan. "Construction of AgrC Proteoliposomes by Detergent-Mediated Method." Acta Chimica Sinica 72, no. 2 (2014): 233. http://dx.doi.org/10.6023/a13111123.

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10

Srivastava, S. K., K. Rajasree, A. Fasim, G. Arakere, and B. Gopal. "Influence of the AgrC-AgrA Complex on the Response Time of Staphylococcus aureus Quorum Sensing." Journal of Bacteriology 196, no. 15 (May 23, 2014): 2876–88. http://dx.doi.org/10.1128/jb.01530-14.

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11

Wang, Li, Lin Qiao, Aike Li, Lixian Chen, Beibei He, Gang Liu, Weiwei Wang, and Jun Fang. "Integrative Multiomics Analysis of the Heat Stress Response of Enterococcus faecium." Biomolecules 13, no. 3 (February 25, 2023): 437. http://dx.doi.org/10.3390/biom13030437.

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A continuous heat-adaptation test was conducted for one Enterococcus faecium (E. faecium) strain wild-type (WT) RS047 to obtain a high-temperature-resistant strain. After domestication, the strain was screened with a significantly higher ability of heat resistance. which is named RS047-wl. Then a multi-omics analysis of transcriptomics and metabolomics was used to analyze the mechanism of the heat resistance of the mutant. A total of 98 differentially expressed genes (DEGs) and 115 differential metabolites covering multiple metabolic processes were detected in the mutant, which indicated that the tolerance of heat resistance was regulated by multiple mechanisms. The changes in AgrB, AgrC, and AgrA gene expressions were involved in quorum-sensing (QS) system pathways, which regulate biofilm formation. Second, highly soluble osmotic substances such as putrescine, spermidine, glycine betaine (GB), and trehalose-6P were accumulated for the membrane transport system. Third, organic acids metabolism and purine metabolism were down-regulated. The findings can provide target genes for subsequent genetic modification of E. faecium, and provide indications for screening heat-resistant bacteria, so as to improve the heat-resistant ability of E. faecium for production.

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12

Somerville, Greg A., Stephen B. Beres, J. Ross Fitzgerald, Frank R. DeLeo, Robert L. Cole, Jessica S. Hoff, and James M. Musser. "In Vitro Serial Passage of Staphylococcus aureus: Changes in Physiology, Virulence Factor Production, and agr Nucleotide Sequence." Journal of Bacteriology 184, no. 5 (March 1, 2002): 1430–37. http://dx.doi.org/10.1128/jb.184.5.1430-1437.2002.

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ABSTRACT Recently, we observed that Staphylococcus aureus strains newly isolated from patients had twofold-higher aconitase activity than a strain passaged extensively in vitro, leading us to hypothesize that aconitase specific activity decreases over time during in vitro passage. To test this hypothesis, a strain recovered from a patient with toxic shock syndrome was serially passaged for 6 weeks, and the aconitase activity was measured. Aconitase specific activity decreased 38% (P < 0.001) by the sixth week in culture. During serial passage, S. aureus existed as a heterogeneous population with two colony types that had pronounced (wild type) or negligible zones of beta-hemolytic activity. The cell density-sensing accessory gene regulatory (agr) system regulates beta-hemolytic activity. Surprisingly, the percentage of colonies with a wild-type beta-hemolytic phenotype correlated strongly with aconitase specific activity (ρ = 0.96), suggesting a common cause of the decreased aconitase specific activity and the variation in percentage of beta-hemolytic colonies. The loss of the beta-hemolytic phenotype also coincided with the occurrence of mutations in the agrC coding region or the intergenic region between agrC and agrA in the derivative strains. Our results demonstrate that in vitro growth is sufficient to result in mutations within the agr operon. Additionally, our results demonstrate that S. aureus undergoes significant phenotypic and genotypic changes during serial passage and suggest that vigilance should be used when extrapolating data obtained from the study of high-passage strains.

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13

Allocca, V., F. Manna, and P. De Vita. "Estimating annual groundwater recharge coefficient for karst aquifers of the southern Apennines (Italy)." Hydrology and Earth System Sciences 18, no. 2 (February 27, 2014): 803–17. http://dx.doi.org/10.5194/hess-18-803-2014.

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Abstract. To assess the mean annual groundwater recharge of the karst aquifers in the southern Apennines (Italy), the estimation of the mean annual groundwater recharge coefficient (AGRC) was conducted by means of an integrated approach based on hydrogeological, hydrological, geomorphological, land use and soil cover analyses. Starting from the hydrological budget equation, the coefficient was conceived as the ratio between the net groundwater outflow and the precipitation minus actual evapotranspiration (P − ETR) for a karst aquifer. A large part of the southern Apennines, which is covered by a meteorological network containing 40 principal karst aquifers, was studied. Using precipitation and air temperature time series gathered through monitoring stations operating in the period 1926–2012, the mean annual P − ETR was estimated, and its distribution was modelled at a regional scale by considering the orographic barrier and rain shadow effects of the Apennine chain, as well as the altitudinal control. Four sample karst aquifers with available long spring discharge time series were identified for estimating the AGRC. The resulting values were correlated with other parameters that control groundwater recharge, such as the extension of outcropping karst rocks, morphological settings, land use and covering soil type. A multiple linear regression between the AGRC, lithology and the summit plateau and endorheic areas was found. This empirical model was used to assess the AGRC and mean annual groundwater recharge in other regional karst aquifers. The coefficient was calculated as ranging between 50 and 79%, thus being comparable with other similar estimations carried out for karst aquifers of European and Mediterranean countries. The mean annual groundwater recharge for karst aquifers of the southern Apennines was assessed by these characterizations and validated by a comparison with available groundwater outflow measurements. These results represent a deeper understanding of an aspect of groundwater hydrology in karst aquifers which is fundamental for the formulation of appropriate management models of groundwater resources at a regional scale, also taking into account mitigation strategies for climate change impacts. Finally, the proposed hydrological characterizations are also supposed to be useful for the assessment of mean annual runoff over carbonate mountains, which is another important topic concerning water management in the southern Apennines.

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14

Jarraud, S., G. J. Lyon, A. M. S. Figueiredo, Lina Gérard, F. Vandenesch, J. Etienne, T. W. Muir, and R. P. Novick. "Exfoliatin-Producing Strains Define a Fourthagr Specificity Group in Staphylococcus aureus." Journal of Bacteriology 182, no. 22 (November 15, 2000): 6517–22. http://dx.doi.org/10.1128/jb.182.22.6517-6522.2000.

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ABSTRACT The staphylococcal virulon is activated by the density-sensingagr system, which is autoinduced by a short peptide (autoinducing peptide [AIP]) processed from a propeptide encoded byagrD. A central segment of the agr locus, consisting of the C-terminal two-thirds of AgrB (the putative processing enzyme), AgrD, and the N-terminal half of AgrC (the receptor), shows striking interstrain variation. This finding has led to the division of Staphylococcus aureus isolates into three different agr specificity groups and to the division of non-aureus staphylococci into a number of others. The AIPs cross-inhibit the agr responses between groups. We have previously shown that most menstrual toxic shock strains belong toagr specificity group III but that no strong clinical identity has been associated with strains of the other two groups. In the present report, we demonstrate a fourth agr specificity group among S. aureus strains and show that most exfoliatin-producing strains belong to this group. A striking common feature of group IV strains is activation of the agrresponse early in exponential phase, at least 2 h earlier than in strains of the other groups. This finding raises the question of the biological significance of the agr autoinduction threshold.

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15

Zhang, Liying, Chunshan Quan, Xuning Zhang, Wen Xiong, and Shengdi Fan. "Proteoliposome‐based model for screening inhibitors targeting histidine kinase AgrC." Chemical Biology & Drug Design 93, no. 5 (March 13, 2019): 712–23. http://dx.doi.org/10.1111/cbdd.13497.

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16

Steiner, Elisabeth, Jamie Scott, Nigel P. Minton, and Klaus Winzer. "AnagrQuorum Sensing System That Regulates Granulose Formation and Sporulation in Clostridium acetobutylicum." Applied and Environmental Microbiology 78, no. 4 (December 16, 2011): 1113–22. http://dx.doi.org/10.1128/aem.06376-11.

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ABSTRACTThe Gram-positive, anaerobic, endospore-forming bacteriumClostridium acetobutylicumhas considerable biotechnological potential due to its ability to produce solvents as fermentation products, in particular the biofuel butanol. Its genome contains a putativeagrlocus,agrBDCA, known in staphylococci to constitute a cyclic peptide-based quorum sensing system. In staphylococci,agrBDis required for the generation of a peptide signal that, upon extracellular accumulation, is sensed by anagrCA-encoded two-component system. Using ClosTron technology,agrB,agrC, andagrAmutants ofC. acetobutylicumATCC 824 were generated and phenotypically characterized. Mutants and wild type displayed similar growth kinetics and no apparent differences in solvent formation under the conditions tested. However, the number of heat-resistant endospores formed by the mutants in liquid culture was reduced by about one order of magnitude. On agar-solidified medium, spore formation was more strongly affected, particularly inagrAandagrCmutants. Similarly, accumulation of the starch-like storage compound granulose was almost undetectable in colonies ofagrB,agrA, andagrCmutants. Importantly, these defects could be genetically complemented, demonstrating that they were directly linked toagrinactivation. A diffusible factor produced byagrBD-expressing strains was found to restore granulose and spore formation in theagrBmutant. Furthermore, a synthetic cyclic peptide, designed on the basis of theC. acetobutylicumAgrD sequence, was also capable of complementing the defects of theagrBmutant when added exogenously to the culture. Together, these findings support the hypothesis thatagr-dependent quorum sensing is involved in the regulation of sporulation and granulose formation inC. acetobutylicum.

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17

George Cisar, Elizabeth A., Edward Geisinger, Tom W. Muir, and Richard P. Novick. "Symmetric signalling within asymmetric dimers of theStaphylococcus aureusreceptor histidine kinase AgrC." Molecular Microbiology 74, no. 1 (October 2009): 44–57. http://dx.doi.org/10.1111/j.1365-2958.2009.06849.x.

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18

Wang, Lina, Chunshan Quan, Wen Xiong, Xiaojing Qu, Shengdi Fan, and Wenzhong Hu. "New insight into transmembrane topology of Staphylococcus aureus histidine kinase AgrC." Biochimica et Biophysica Acta (BBA) - Biomembranes 1838, no. 3 (March 2014): 988–93. http://dx.doi.org/10.1016/j.bbamem.2013.12.006.

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19

Geisinger, Edward, Elizabeth A. George, John Chen, Tom W. Muir, and Richard P. Novick. "Identification of ligand specificity determinants in AgrC, theStaphylococcus aureusquorum-sensing receptor." Journal of Biological Chemistry 287, no. 22 (May 25, 2012): 18588. http://dx.doi.org/10.1074/jbc.a112.710227.

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20

Geisinger, Edward, Elizabeth A. George, Tom W. Muir, and Richard P. Novick. "Identification of Ligand Specificity Determinants in AgrC, theStaphylococcus aureusQuorum-sensing Receptor." Journal of Biological Chemistry 283, no. 14 (January 25, 2008): 8930–38. http://dx.doi.org/10.1074/jbc.m710227200.

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21

Li, Wei, Xiaoyu Ma, Yumin Chen, Bin Dai, Runjing Chen, Chao Tang, Youmeng Luo, and Kaiqiang Zhang. "Random Fuzzy Granular Decision Tree." Mathematical Problems in Engineering 2021 (June 9, 2021): 1–17. http://dx.doi.org/10.1155/2021/5578682.

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In this study, the classification problem is solved from the view of granular computing. That is, the classification problem is equivalently transformed into the fuzzy granular space to solve. Most classification algorithms are only adopted to handle numerical data; random fuzzy granular decision tree (RFGDT) can handle not only numerical data but also nonnumerical data like information granules. Measures can be taken in four ways as follows. First, an adaptive global random clustering (AGRC) algorithm is proposed, which can adaptively find the optimal cluster centers and maximize the ratio of interclass standard deviation to intraclass standard deviation, and avoid falling into local optimal solution; second, on the basis of AGRC, a parallel model is designed for fuzzy granulation of data to construct granular space, which can greatly enhance the efficiency compared with serial granulation of data; third, in the fuzzy granular space, we design RFGDT to classify the fuzzy granules, which can select important features as tree nodes based on information gain ratio and avoid the problem of overfitting based on the pruning algorithm proposed. Finally, we employ the dataset from UC Irvine Machine Learning Repository for verification. Theory and experimental results prove that RFGDT has high efficiency and accuracy and is robust in solving classification problems.

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22

Wang, Boyuan, Aishan Zhao, Qian Xie, Paul Dominic Olinares, Brian T. Chait, Richard P. Novick, and Tom W. Muir. "Functional Plasticity of the AgrC Receptor Histidine Kinase Required for Staphylococcal Virulence." Cell Chemical Biology 24, no. 1 (January 2017): 76–86. http://dx.doi.org/10.1016/j.chembiol.2016.12.008.

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23

AL-Sabaawy, Abeer Mahmood, Enas Abdul-muniem., AL-Layla, and Omar Ibrahim AL-Sabaawy. "Detection of bacterial infection of the eye chalazion in Mosul City." Science Archives 03, no. 04 (2022): 240–46. http://dx.doi.org/10.47587/sa.2022.3401.

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Chalazion is a common infection of the meibomian gland in all ages’ eyelids. The current study sought to isolate and identify bacteria linked with chalazion in patients hospitalized to Mosul hospitals between 10/1/2021 and 1/3/2022. Samples were obtained using swabs soaked in the transport media (amies), and bacteria were identified using traditional methods with API20E. Vitek-2 and molecular approaches based on the 16 S rRNA gene verified the species-level diagnosis. Using BLAST software, the nitrogen base sequences were determined and compared to those of the NCBI. The results showed that Staphylococcus aureus was isolated by 52.2% and 62.5% among women, notably in the age (21-40) years, and by 27.8% for females and 19.2% for the same age group in males, and upper eyelid infection predominated. The infection rate in people with oily skin was 50.9% in females and 34.6% in men, with the presence of the agr A, agrC, and agrD genes in isolates that exhibited a positive result in the Congo red medium and microtiter plate.

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24

Lina, Gerard, Sophie Jarraud, Guangyong Ji, Timothy Greenland, Alicia Pedraza, Jerome Etienne, Richard P. Novick, and François Vandenesch. "Transmembrane topology and histidine protein kinase activity of AgrC, theagrsignal receptor inStaphylococcus aureus." Molecular Microbiology 28, no. 3 (April 1998): 655–62. http://dx.doi.org/10.1046/j.1365-2958.1998.00830.x.

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25

Qin, Xiang, Kavindra V. Singh, George M. Weinstock, and Barbara E. Murray. "Effects of Enterococcus faecalis fsrGenes on Production of Gelatinase and a Serine Protease and Virulence." Infection and Immunity 68, no. 5 (May 1, 2000): 2579–86. http://dx.doi.org/10.1128/iai.68.5.2579-2586.2000.

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ABSTRACT Three agr-like genes (fsrA,fsrB, and fsrC, for Enterococcus faecalis regulator) were found upstream of the previously reported gelatinase gene (gelE) and a downstream putative serine protease gene (sprE; accession number Z12296 ) ofEnterococcus faecalis OG1RF. The deduced amino acid sequence of fsrA shows 26% identity and 38% similarity toStaphylococcus aureus AgrA (the response regulator of the accessory gene regulator system in the agr locus), FsrB shows 23% identity and 41% similarity to S. aureus AgrB, and FsrC shows 23% identity and 36% similarity to S. aureus AgrC (the sensor transducer of Agr system). Northern blot analysis suggested that gelE and sprE are cotranscribed and that fsrB and fsrC are also cotranscribed in OG1RF. Northern blot analysis of fsrA,fsrB, fsrC, gelE, andsprE insertion mutants showed that fsrB,fsrC, gelE, and sprE are not expressed in fsrA, fsrB, and fsrCmutants, while insertion in an open reading frame further upstream offsrA did not effect the expression of these genes, suggesting that agr-like genes may be autoregulated and that they regulate gelE and sprE expression, as further confirmed by complementation of fsr gene mutations with a 6-kb fragment which contains all three fsr genes in the shuttle vector, pAT18. Testing of 95 other isolates of E. faecalis showed that 62% produced gelatinase (Gel+), while 91% (including all Gel+ strains) hybridized to agelE probe; 71% (including all Gel+ strains) hybridized to an fsr probe, corroborating the conclusion that both gelE and fsr are necessary for gelatinase production. Testing of fsrA, fsrB, and sprE mutants in a mouse peritonitis model showed that sprE and agr-like gene mutants resulted in highly significantly prolonged survival compared to the parent strain OG1RF, a finding similar to what we had previously shown for agelE mutant. These results suggest that sprEand agr-like genes contribute to the virulence of E. faecalis OG1RF in this model.

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Oliveira, Edenis Cesar. "Influência da variável ambiental no processo de escolha dos fornecedores: Um Estudo em Agroindústrias da Microrregião de Assis-SP." Revista Produção e Desenvolvimento 2, no. 2 (August 30, 2016): 77–100. http://dx.doi.org/10.32358/rpd.2016.v2.117.

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The global market characterized by competition, has demanded of new placements organizations, particularly as to how implement and develop relations with its trading partners. The Supply Chain Management emerges as a tool that provides organizations with the most effective management of the consequences of these relations. The incorporation of environmental issues in the organizational context reflected directly across chain. Organizations began to consider sustainability as a major factor in relations with its stakeholders, justifying the emergence of Sustainable Management of Supply Chain. The study aims to analyze the influence of environmental variable introduced in decisions and selection of suppliers of sugarcane agro-industries located in the micro-region of Assis-SP. Was held from Multiple Case Study in six agribusinesses, collecting data through semi-structured interviews, applied to sixteen actors directly involved with the subject matter, in addition to document analysis to support the interviews. For data analysis, applied to content analysis with the help of ATLAS.ti software. The results showed that, of the six surveyed companies, in agribusiness AGR2, FOR1 and for2 the environmental variable has a weak influence in the selection of its suppliers; in AGR1 the influence is average and only in AGR3 and AGR4 agribusinesses environmental variable has a strong influence.

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Xiang, Bingquan, Yujie Lei, Ya Chen, Guangqiang Zhao, Yongchun Zhou, Youquan Zhou, Yunchao Huang, and Lianhua Ye. "Mechanistic study on the inhibition of Staphylococcus epidermidis biofilm by agrC-specific binding polypeptide." Annals of Translational Medicine 8, no. 6 (March 2020): 337. http://dx.doi.org/10.21037/atm.2020.02.84.

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Wang, Lina, Chunshan Quan, Baoquan Liu, Jianfeng Wang, Wen Xiong, Pengchao Zhao, and Shengdi Fan. "Functional Reconstitution of Staphylococcus aureus Truncated AgrC Histidine Kinase in a Model Membrane System." PLoS ONE 8, no. 11 (November 26, 2013): e80400. http://dx.doi.org/10.1371/journal.pone.0080400.

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Huang, Qian, Yihui Xie, Ziyu Yang, Danhong Cheng, Lei He, Hua Wang, Qian Liu, and Min Li. "The cytoplasmic loops of AgrC contribute to the quorum-sensing activity of Staphylococcus aureus." Journal of Microbiology 59, no. 1 (November 17, 2020): 92–100. http://dx.doi.org/10.1007/s12275-021-0274-x.

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Dmitrenko, Olga, Andrey Chaplin, Anna Balbutskaya, Tamara Pkhakadze, and Sergey Alkhovsky. "In Silico Genome-Scale Analysis of Molecular Mechanisms Contributing to the Development of a Persistent Infection with Methicillin-Resistant Staphylococcus aureus (MRSA) ST239." International Journal of Molecular Sciences 23, no. 24 (December 16, 2022): 16086. http://dx.doi.org/10.3390/ijms232416086.

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The increasing frequency of isolation of methicillin-resistant Staphylococcus aureus (MRSA) limits the chances for the effective antibacterial therapy of staphylococcal diseases and results in the development of persistent infection such as bacteremia and osteomyelitis. The aim of this study was to identify features of the MRSAST239 0943-1505-2016 (SA943) genome that contribute to the formation of both acute and chronic musculoskeletal infections. The analysis was performed using comparative genomics data of the dominant epidemic S. aureus lineages, namely ST1, ST8, ST30, ST36, and ST239. The SA943 genome encodes proteins that provide resistance to the host’s immune system, suppress immunological memory, and form biofilms. The molecular mechanisms of adaptation responsible for the development of persistent infection were as follows: amino acid substitution in PBP2 and PBP2a, providing resistance to ceftaroline; loss of a large part of prophage DNA and restoration of the nucleotide sequence of beta-hemolysin, that greatly facilitates the escape of phagocytosed bacteria from the phagosome and formation of biofilms; dysfunction of the AgrA system due to the presence of psm-mec and several amino acid substitutions in the AgrC; partial deletion of the nucleotide sequence in genomic island vSAβ resulting in the loss of two proteases of Spl—operon; and deletion of SD repeats in the SdrE amino acid sequence.

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Yang, Tian, Yftah Tal-Gan, Alexandra E. Paharik, Alexander R. Horswill, and Helen E. Blackwell. "Structure–Function Analyses of aStaphylococcus epidermidisAutoinducing Peptide Reveals Motifs Critical for AgrC-type Receptor Modulation." ACS Chemical Biology 11, no. 7 (May 18, 2016): 1982–91. http://dx.doi.org/10.1021/acschembio.6b00120.

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Chan, Weng C., Barry J. Coyle, and Paul Williams. "Virulence Regulation and Quorum Sensing in Staphylococcal Infections: Competitive AgrC Antagonists as Quorum Sensing Inhibitors§." Journal of Medicinal Chemistry 47, no. 19 (September 2004): 4633–41. http://dx.doi.org/10.1021/jm0400754.

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Wang, Boyuan, Aishan Zhao, Richard P. Novick, and Tom W. Muir. "Activation and Inhibition of the Receptor Histidine Kinase AgrC Occurs through Opposite Helical Transduction Motions." Molecular Cell 53, no. 6 (March 2014): 929–40. http://dx.doi.org/10.1016/j.molcel.2014.02.029.

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Hansen, Anna Mette, Pai Peng, Mara Baldry, Iris Perez-Gassol, Simon B. Christensen, Joachim Møllesøe Obel Vinther, Hanne Ingmer, and Henrik Franzyk. "Lactam hybrid analogues of solonamide B and autoinducing peptides as potent S. aureus AgrC antagonists." European Journal of Medicinal Chemistry 152 (May 2018): 370–76. http://dx.doi.org/10.1016/j.ejmech.2018.04.053.

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Spiegel, Christopher, Stephan Josef Maria Steixner, and Débora C. Coraça-Huber. "Antibiofilm Activity of Omega-3 Fatty Acids and Its Influence on the Expression of Biofilm Formation Genes on Staphylococcus aureus." Antibiotics 11, no. 7 (July 11, 2022): 932. http://dx.doi.org/10.3390/antibiotics11070932.

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Background: Currently, 1–2% of all prosthetic joint surgeries are followed by an infection. These infections cause approximately 4% of deaths in the first year after surgery, while the 5-year mortality rate is up to 21%. Prosthetic joint infections are mainly caused by Staphylococcus aureus or Staphylococcus epidermis strains. Both species share the capability of biofilm formation and methicillin resistance. The formation of biofilm helps bacterial cells to withstand critical environmental conditions. Due to their tolerance against antibacterial substances, biofilms are a significant problem in modern medicine. Alternatives for the use of methicillin as a therapeutic are not yet widespread. The use of omega-3 fatty acids, such as docosahexaenoic acid, may help against prosthetic joint infections and lower mortality rates. The aim of this study is to evaluate if docosahexaenoic acid offers a safe anti-biofilm activity against Staphylococcus aureus and MRSA without enhancing icaADBC-dependent biofilm formation or additional stress responses, therefore enhancing antibiotic tolerance and resistance. Methods: In this study, we examined the gene expression of biofilm-associated genes and regulators. We performed RT-qPCR after RNA extraction of Staphylococcus aureus ATCC 29213 and one clinical MRSA strain. We compared gene expression of icaADBC, SarA, SigB, and agrAC under the influence of 1.25 mg /L and 0.625 mg/L of docosahexaenoic acid to their controls. Results: We found a higher expression of regulatory genes such as SarA, SigB, agrA, and agrC at 1.25 mg/L of docosahexaenoic acid in ATCC 29213 and a lower increase in gene expression levels in clinical MRSA isolates. icaADBC was not affected in both strains at both concentration levels by docosahexaenoic acid. Conclusions: Docosahexaenoic acid does not enhance icaADBC-dependent biofilm formation while still reducing bacterial CFU in biofilms. Docosahexaenoic acid can be considered an option as a therapeutic substance against biofilm formation and may be a good alternative in reducing the risk of MRSA formation.

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Qazi, Saara, Barry Middleton, Siti Hanna Muharram, Alan Cockayne, Philip Hill, Paul O'Shea, Siri Ram Chhabra, Miguel Cámara, and Paul Williams. "N-Acylhomoserine Lactones Antagonize Virulence Gene Expression and Quorum Sensing in Staphylococcus aureus." Infection and Immunity 74, no. 2 (February 2006): 910–19. http://dx.doi.org/10.1128/iai.74.2.910-919.2006.

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ABSTRACT Many gram-negative bacteria employ N-acylhomoserine lactone (AHL)-mediated quorum sensing to control virulence. To determine whether gram-positive bacteria such as Staphylococcus aureus respond to AHLs, we used a growth-dependent lux reporter fusion. Exposure of S. aureus to different AHLs revealed that 3-oxo-substituted AHLs with C10 to C14 acyl chains inhibited light output and growth in a concentration-dependent manner, while short-chain AHLs had no effect. N-(3-Oxododecanoyl)-l-homoserine lactone (3-oxo-C12-HSL) inhibited the production of exotoxins and cell wall fibronectin-binding proteins but enhanced protein A expression. Since these processes are reciprocally regulated via the S. aureus agr quorum-sensing system, which in turn, is regulated via sar, we examined the effect of AHLs on sarA and agr. At sub-growth-inhibitory concentrations of 3-oxo-C12-HSL, both sarA expression and agr expression were inhibited, indicating that the action of 3-oxo-C12-HSL is mediated at least in part through antagonism of quorum sensing in S. aureus. Spent culture supernatants from Pseudomonas aeruginosa, which produces both 3-oxo-C12-HSL and N-butanoyl-homoserine lactone (C4-HSL), also inhibited agr expression, although C4-HSL itself was inactive in this assay. Since quorum sensing in S. aureus depends on the activities of membrane-associated proteins, such as AgrB, AgrC, and AgrD, we investigated whether AHLs perturbed S. aureus membrane functionality by determining their influence on the membrane dipole potential. From the binding curves obtained, a dissociation constant of 7 μM was obtained for 3-oxo-C12-HSL, indicating the presence of a specific saturable receptor, whereas no binding was observed for C4-HSL. These data demonstrate that long-chain 3-oxo-substituted AHLs, such as 3-oxo-C12-HSL, are capable of interacting with the S. aureus cytoplasmic membrane in a saturable, specific manner and at sub-growth-inhibitory concentrations, down-regulating exotoxin production and both sarA and agr expression.

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Vasquez, Joseph K., and Helen E. Blackwell. "Simplified Autoinducing Peptide Mimetics with Single-Nanomolar Activity Against the Staphylococcus aureus AgrC Quorum Sensing Receptor." ACS Infectious Diseases 5, no. 4 (February 28, 2019): 484–92. http://dx.doi.org/10.1021/acsinfecdis.9b00002.

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Zorzet, A., J. M. Andersen, A. I. Nilsson, N. F. Moller, and D. I. Andersson. "Compensatory mutations in agrC partly restore fitness in vitro to peptide deformylase inhibitor-resistant Staphylococcus aureus." Journal of Antimicrobial Chemotherapy 67, no. 8 (May 10, 2012): 1835–42. http://dx.doi.org/10.1093/jac/dks168.

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Tal-Gan, Yftah, Monika Ivancic, Gabriel Cornilescu, Tian Yang, and Helen E. Blackwell. "Highly Stable, Amide-Bridged Autoinducing Peptide Analogues that Strongly Inhibit the AgrC Quorum Sensing Receptor inStaphylococcus aureus." Angewandte Chemie International Edition 55, no. 31 (June 8, 2016): 8913–17. http://dx.doi.org/10.1002/anie.201602974.

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Tal-Gan, Yftah, Monika Ivancic, Gabriel Cornilescu, Tian Yang, and Helen E. Blackwell. "Highly Stable, Amide-Bridged Autoinducing Peptide Analogues that Strongly Inhibit the AgrC Quorum Sensing Receptor inStaphylococcus aureus." Angewandte Chemie 128, no. 31 (June 8, 2016): 9059–63. http://dx.doi.org/10.1002/ange.201602974.

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Botelho, Ana M. N., Maiana O. C. Costa, Cristiana O. Beltrame, Fabienne A. Ferreira, Nicholas C. B. Lima, Bruno S. S. Costa, Guilherme L. de Morais, et al. "Complete Genome Sequence of the MRSA Isolate HC1335 from ST239 Lineage Displaying a Truncated AgrC Histidine Kinase Receptor." Genome Biology and Evolution 8, no. 10 (September 15, 2016): 3187–92. http://dx.doi.org/10.1093/gbe/evw225.

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Broderick, Adam H., Danielle M. Stacy, Yftah Tal-Gan, Michael J. Kratochvil, Helen E. Blackwell, and David M. Lynn. "Surface Coatings that Promote Rapid Release of Peptide-Based AgrC Inhibitors for Attenuation of Quorum Sensing inStaphylococcus aureus." Advanced Healthcare Materials 3, no. 1 (June 28, 2013): 97–105. http://dx.doi.org/10.1002/adhm.201300119.

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Wang, Boyuan, Aishan Zhao, Richard P. Novick, and Tom W. Muir. "Key driving forces in the biosynthesis of autoinducing peptides required for staphylococcal virulence." Proceedings of the National Academy of Sciences 112, no. 34 (August 10, 2015): 10679–84. http://dx.doi.org/10.1073/pnas.1506030112.

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Staphylococci produce autoinducing peptides (AIPs) as quorum-sensing signals that regulate virulence. These AIPs feature a thiolactone macrocycle that connects the peptide C terminus to the side chain of an internal cysteine. AIPs are processed from ribosomally synthesized precursors [accessory gene regulator D (AgrD)] through two proteolytic events. Formation of the thiolactone is coupled to the first of these and involves the activity of the integral membrane protease AgrB. This step is expected to be thermodynamically unfavorable, and therefore, it is unclear how AIP-producing bacteria produce sufficient amounts of the thiolactone-containing intermediate to drive quorum sensing. Herein, we present the in vitro reconstitution of the AgrB-dependent proteolysis of an AgrD precursor from Staphylococcus aureus. Our data show that efficient thiolactone production is driven by two unanticipated features of the system: (i) membrane association of the thiolactone-containing intermediate, which stabilizes the macrocycle, and (ii) rapid degradation of the C-terminal proteolysis fragment AgrDC, which affects the reaction equilibrium position. Cell-based studies confirm the intimate link between AIP production and intracellular AgrDC levels. Thus, our studies explain the chemical principles that drive AIP production, including uncovering a hitherto unknown link between quorum sensing and peptide turnover.

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Wang, Lina, Chunshan Quan, Baoquan Liu, Yongbin Xu, Pengchao Zhao, Wen Xiong, and Shengdi Fan. "Green Fluorescent Protein (GFP)-Based Overexpression Screening and Characterization of AgrC, a Receptor Protein of Quorum Sensing in Staphylococcus aureus." International Journal of Molecular Sciences 14, no. 9 (September 6, 2013): 18470–87. http://dx.doi.org/10.3390/ijms140918470.

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Jensen, Rasmus O., Klaus Winzer, Simon R. Clarke, Weng C. Chan, and Paul Williams. "Differential Recognition of Staphylococcus aureus Quorum-Sensing Signals Depends on Both Extracellular Loops 1 and 2 of the Transmembrane Sensor AgrC." Journal of Molecular Biology 381, no. 2 (August 2008): 300–309. http://dx.doi.org/10.1016/j.jmb.2008.06.018.

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O’Keeffe, Triona, Colin Hill, and R. Paul Ross. "Characterization and Heterologous Expression of the Genes Encoding Enterocin A Production, Immunity, and Regulation inEnterococcus faecium DPC1146." Applied and Environmental Microbiology 65, no. 4 (April 1, 1999): 1506–15. http://dx.doi.org/10.1128/aem.65.4.1506-1515.1999.

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ABSTRACT Enterocin A is a small, heat-stable, antilisterial bacteriocin produced by Enterococcus faecium DPC1146. The sequence of a 10,879-bp chromosomal region containing at least 12 open reading frames (ORFs), 7 of which are predicted to play a role in enterocin biosynthesis, is presented. The genes entA,entI, and entF encode the enterocin A prepeptide, the putative immunity protein, and the induction factor prepeptide, respectively. The deduced proteins EntK and EntR resemble the histidine kinase and response regulator proteins of two-component signal transducing systems of the AgrC-AgrA type. The predicted proteins EntT and EntD are homologous to ABC (ATP-binding cassette) transporters and accessory factors, respectively, of several other bacteriocin systems and to proteins implicated in the signal-sequence-independent export of Escherichia colihemolysin A. Immediately downstream of the entT andentD genes are two ORFs, the product of one of which, ORF4, is very similar to the product of the yteI gene ofBacillus subtilis and to E. coli protease IV, a signal peptide peptidase known to be involved in outer membrane lipoprotein export. Another potential bacteriocin is encoded in the opposite direction to the other genes in the enterocin cluster. This putative bacteriocin-like peptide is similar to LafX, one of the components of the lactacin F complex. A deletion which included one of two direct repeats upstream of the entA gene abolished enterocin A activity, immunity, and ability to induce bacteriocin production. Transposon insertion upstream of the entF gene also had the same effect, but this mutant could be complemented by exogenously supplied induction factor. The putative EntI peptide was shown to be involved in the immunity to enterocin A. Cloning of a 10.5-kb amplicon comprising all predicted ORFs and regulatory regions resulted in heterologous production of enterocin A and induction factor in Enterococcus faecalis, while a four-gene construct (entAITD) under the control of a constitutive promoter resulted in heterologous enterocin A production in both E. faecalis and Lactococcus lactis.

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James, Ellen H., Andrew M. Edwards, and Sivaramesh Wigneshweraraj. "Transcriptional downregulation ofagrexpression inStaphylococcus aureusduring growth in human serum can be overcome by constitutively active mutant forms of the sensor kinase AgrC." FEMS Microbiology Letters 349, no. 2 (November 18, 2013): 153–62. http://dx.doi.org/10.1111/1574-6968.12309.

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Cunha, Isadora Luiza Climaco, Fábio Rosa, and Luiz Kulay. "Green Coalescent Synthesis Based on the Design for Environment (DfE) Principles: Brazilian Experience." Sustainability 13, no. 22 (November 19, 2021): 12802. http://dx.doi.org/10.3390/su132212802.

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Coalescents are compounds with a high potential for generating tropospheric ozone, which causes adverse effects on humans and their surroundings. This study designed a coalescent for decorative paints that reached technical levels equivalent to those obtained by StC, a product on the market, but with better environmental and economic performance. The strategy adopted in creating the green coalescent (GrC) improved film formation and reduced the product’s atmospheric emission rate. Regarding the environmental performance, GrC outperformed StC in terms of water consumption, global warming potential, and human toxicity by 30%, 35%, and 91%, but had a high smog formation potential even with a reduced loss to the air. The redesign of the molecule gave rise to AGrC, which achieved a more homogeneous environmental performance. The results of an economic analysis indicated that the procedures adopted to reduce environmental impacts could also make the coalescent more competitive if the lowest market prices were practiced. On the other hand, if the products are sold at high prices, the paint industry tends to privilege the economic dimension and disregard environmental performance for decision purposes. This research succeeded in reconciling technical functions and aspects related to sustainability to design more competitive products in the Brazilian market.

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Pulia, Michael S., Jennifer Anderson, Zhan Ye, Noha S. Elsayed, Thao Le, Jacob Patitucci, Krishna Ganta, Matthew Hall, Vineet K. Singh, and Sanjay K. Shukla. "Expression of Staphylococcal Virulence Genes In Situ in Human Skin and Soft Tissue Infections." Antibiotics 11, no. 4 (April 14, 2022): 527. http://dx.doi.org/10.3390/antibiotics11040527.

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Background: Staphylococcus aureus, the most common pathogen in skin and soft tissue infections (SSTI), harbors many well-characterized virulence genes. However, the expression of many of them in SSTIs is unknown. In this study, S. aureus virulence genes expressed in SSTI were investigated. Methods: Fifty-three subjects presenting to the outpatient’s care and emergency departments with a purulent SSTI at two medical centers in Wisconsin, USA, were enrolled in the study. Total mRNA was extracted from the purulent or swab materials, made into cDNA and sequenced on MiSeq platform. The relative cDNA counts to gmk and identifications of the transcripts were carried out with respect to USA300 reference genome and using SAMTOOLS v.1.3 and BWA, respectively. Result: A significantly higher cDNA count was observed for many of the virulence and regulatory gene transcripts in the pus samples compared to the swab samples relative to the cDNA counts for gmk, a housekeeping gene. They were for lukS-PV (18.6 vs. 14.2), isaA (13.4 vs. 8.5), ssaA (4.8 vs. 3.1), hlgC (1.4 vs. 1.33), atl (17.7 vs. 8.33), clfA (3.9 vs. 0.83), eno (6.04 vs. 3.16), fnbA (5.93 vs. 0.33), saeS (6.3 vs. 1.33), saeR (5.4 vs. 3.33) and agrC (5.6 vs. 1.5). Conclusions: A relative increase in the transcripts of several toxins, adhesion and regulatory genes with respect to a gmk in purulent materials suggests their role in situ during SSTIs, perhaps in an orchestrated manner.

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Aquino Rocha, Joaquin Humberto, and Lidianne do Nascimento Farias. "Fluência de concreto com agregados reciclados: uma revisão." E&S Engineering and Science 11, no. 1 (April 30, 2022): 1–21. http://dx.doi.org/10.18607/es20221113309.

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A fluência é uma das propriedades mais importantes do concreto, mas o uso de Agregados Reciclados de Concreto (ARC) pode afetar significativamente essa propriedade. Neste sentido, o objetivo do presente artigo foi realizar uma revisão da literatura sobre a fluência no concreto com ARC, considerando sua influência, causas e medidas de redução. A metodologia consistiu em uma Revisão Sistemática da Literatura (RSL) para o período de tempo de 2007 até 2021 (primeiro trimestre). Foram utilizadas diferentes bases de dados de busca de informação científica, limitando-se a artigos de revista e em língua inglesa. Os resultados mostram que o Agregado Graúdo Reciclado de Concreto (AGRC) é o mais utilizado nos estudos selecionados, aumentado a fluência com o grau de substituição do agregado natural; no entanto, não há uma tendência clara com Agregado Fino Reciclado de Concreto (AFRC), cujos resultados são limitados na literatura. Apresenta-se que a fluência depende de vários fatores como a relação a/c, idade da carga, etc. Entre a principais causas, a maioria dos estudos afirma que a fluência se deve à argamassa antiga aderida ao ARC, mas também algumas medidas são propostas para reduzir a fluência no concreto com ARC. Pode-se concluir que o uso de ARC é uma alternativa sustentável para a produção de concreto, mas são necessárias mais pesquisas para entender completamente a influência do ARC na fluência do concreto e consolidar seu uso para níveis industriais.

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