Your browser doesn't support javascript.
loading
Mostrar: 20 | 50 | 100
Resultados 1 - 20 de 12.718
Filtrar
1.
Nat Commun ; 11(1): 4963, 2020 10 02.
Artigo em Inglês | MEDLINE | ID: mdl-33009406

RESUMO

Bacterial nanotubes are membranous structures that have been reported to function as conduits between cells to exchange DNA, proteins, and nutrients. Here, we investigate the morphology and formation of bacterial nanotubes using Bacillus subtilis. We show that nanotube formation is associated with stress conditions, and is highly sensitive to the cells' genetic background, growth phase, and sample preparation methods. Remarkably, nanotubes appear to be extruded exclusively from dying cells, likely as a result of biophysical forces. Their emergence is extremely fast, occurring within seconds by cannibalizing the cell membrane. Subsequent experiments reveal that cell-to-cell transfer of non-conjugative plasmids depends strictly on the competence system of the cell, and not on nanotube formation. Our study thus supports the notion that bacterial nanotubes are a post mortem phenomenon involved in cell disintegration, and are unlikely to be involved in cytoplasmic content exchange between live cells.


Assuntos
Bacillus subtilis/citologia , Bacillus subtilis/metabolismo , Viabilidade Microbiana , Nanotubos/química , Bacillus subtilis/genética , Bacillus subtilis/ultraestrutura , Conjugação Genética , DNA Bacteriano/genética , Plasmídeos/genética
2.
J. Health NPEPS ; 5(2)set. 2020.
Artigo em Português | LILACS, BDENF - Enfermagem | ID: biblio-1120029

RESUMO

Objetivo: verificar a persistência do SARS-CoV-2 nas diferentes superfícies e medidas preventivas contra a transmissão do vírus. Método: revisão sistemática norteada pelo método PRISMA. Foram utilizadas as bases de buscas PubMed e LILACS de janeiro a junho de 2020, com os descritores: "2019-nCOV" OR "SARS-CoV-2" OR "COVID-19" AND "transmission" OR "transmission route" AND "viability" AND "surface" OR "inanimate surface" AND "prevention". As informações extraídas foram autor/ano, país, tipo de publicação, nome da revista, idioma, país da publicação e base de dados. Resultados: foram identificadas 178 publicações, com exclusão de 164 artigos, nove por idioma, 12 por outras doenças e/ou patógenos e 143 pelo título e/ou resumo. Foram incluídos 14 artigos qualitativos, oito artigos de revisões narrativas, uma comunicação breve, dois artigos originais e um editorial. Treze artigos foram publicados em inglês e um em português. Conclusão: coronavírus humanos (HCoV 229E) podem se manter em diferentes superfícies durante duas horas até nove dias. Baixas temperaturas e reduzida umidade relativa do ar favorecem a sobrevivência do SARS-CoV-2, sendo mais estável em plásticos e aço inoxidável do que em cobre e papelão. A recomendação é higienização de superfícies e mãos com água, sabão ou higienizadores à base de álcool.(AU)


Objective: to verify the persistence of SARS-CoV-2 on different types of surfaces and the preventive measures against the transmission of the virus. Method: a systematic review was carried out, using the PRISMA method. The PubMed and LILACS databases from January to June 2020 were used, with the following descriptors: "2019-nCOV" OR "SARS-CoV-2" OR "COVID-19" AND "transmission" OR "transmission route" AND "viability" AND "surface" OR "inanimate surface" AND "prevention". Information extracted was author/year, country, type of publication, journal name, language, country of publication and database. Results: 178 publications were identified. 164 articles were excluded, nine by language, 12 by other diseases and/or pathogens and 143 by title and/or abstract. 14 qualitative articles were included, eight articles of narrative reviews, one short communication, two original articles and one editorial. Thirteen articles were published in English and one in Portuguese. Conclusion: human coronaviruses (HCoV 229E) can persist on different surfaces for two hours up to nine days. Low temperatures and low relative humidity of the air favor the survival of SARS-CoV-2, which is more stable on plastics and on stainless steel than on copper and cardboard. The recommendation is frequent surface and hand hygiene with water, soap or alcohol-based rubs.(AU)


Objetivo: verificar la persistencia del SARS-CoV-2 en diferentes superficies y las medidas preventivas contra la transmisión del virus. Método: se realizó una revisión sistemática, utilizando el método PRISMA. Se utilizaron las bases de datos de búsqueda de PubMed y LILACS de enero a junio de 2020, con los descriptores: "2019-nCOV" O "SARS-CoV-2" O "COVID-19" Y "transmisión" O "ruta de transmisión" Y "viabilidad" Y "superficie" O "superficie inanimada" Y "prevención". Las informaciones extraídas fueron autor / año, país, tipo de publicación, nombre de la revista, idioma, país de publicación y base de datos. Resultados: se identificaron 178 publicaciones. Se excluyeron 164 artículos, nueve por idioma, 12 por otras enfermedades y/o patógenos y 143 por título y/o resumen, incluidos 14 artículos cualitativos, ocho artículos de revisiones narrativas, una comunicación breve, dos artículos originales y uno editorial. Se publicaron trece artículos en inglés y uno en portugués. Conclusión: los coronavirus humanos (HCoV 229E) pueden matenerse en diferentes superficies durante dos horas hasta nueve días. Las bajas temperaturas y la reducida humedad relativa del aire favorecen la supervivencia del SARS-CoV-2, siendo más estable en plásticos y acero inoxidable que en cobre y carton. La recomendación es limpiar superficies y manos con agua, jabón o limpiadores a base de alcohol.(AU)


Assuntos
Humanos , Infecções por Coronavirus/prevenção & controle , Prevenção de Doenças , Viabilidade Microbiana , Betacoronavirus/isolamento & purificação , Higiene das Mãos
3.
Viruses ; 12(9)2020 09 22.
Artigo em Inglês | MEDLINE | ID: mdl-32971954

RESUMO

The relationship between parasite virulence and transmission is a pillar of evolutionary theory that has implications for public health. Part of this canon involves the idea that virulence and free-living survival (a key component of transmission) may have different relationships in different host-parasite systems. Most examinations of the evolution of virulence-transmission relationships-Theoretical or empirical in nature-Tend to focus on the evolution of virulence, with transmission being a secondary consideration. Even within transmission studies, the focus on free-living survival is a smaller subset, though recent studies have examined its importance in the ecology of infectious diseases. Few studies have examined the epidemic-scale consequences of variation in survival across different virulence-survival relationships. In this study, we utilize a mathematical model motivated by aspects of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) natural history to investigate how evolutionary changes in survival may influence several aspects of disease dynamics at the epidemiological scale. Across virulence-survival relationships (where these traits are either positively or negatively correlated), we found that small changes (5% above and below the nominal value) in survival can have a meaningful effect on certain outbreak features, including R0, and on the size of the infectious peak in the population. These results highlight the importance of properly understanding the mechanistic relationship between virulence and parasite survival, as the evolution of increased survival across different relationships with virulence may have considerably different epidemiological signatures.


Assuntos
Betacoronavirus/fisiologia , Betacoronavirus/patogenicidade , Infecções por Coronavirus/transmissão , Pneumonia Viral/transmissão , Número Básico de Reprodução , Evolução Biológica , Infecções por Coronavirus/epidemiologia , Infecções por Coronavirus/virologia , Interações Hospedeiro-Patógeno , Humanos , Viabilidade Microbiana , Modelos Biológicos , Pandemias , Pneumonia Viral/epidemiologia , Pneumonia Viral/virologia , Prevalência , Virulência
4.
Int J Nanomedicine ; 15: 5813-5824, 2020.
Artigo em Inglês | MEDLINE | ID: mdl-32821103

RESUMO

Introduction: This paper presents a novel technique for the synthesis of graphene oxide (GO) with various surface features using high-density atmospheric plasma deposition. Furthermore, to investigate the use of hydrophobic, super-hydrophobic, and hydrophilic graphene in biological applications, we synthesized hydrophobic, super-hydrophobic, and hydrophilic graphene oxides by additional heat treatment and argon plasma treatment, respectively. In contrast to conventional fabrication procedures, reduced graphene oxide (rGO) formed under low pressure and high-temperature environment using a new synthesis method-developed and described in this study-offers a convenient deposition method on any kind surface with controlled wettability. Methods: High density at atmospheric plasma is used for the synthesis of rGO and GO and its biocompatibility based on various wetting properties was evaluated using MTT (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide) assay, and the viability of cells in response to rGO and GO with various surface features was investigated. Structural integrity was characterized by Raman spectroscopy, FESEM and FE-TEM. Wettability was measured via contact angle method and confirmed with XPS analysis. Results: We found that GO coating with a hydrophilic feature is more biocompatible than other surfaces as observed in case of fibroblast cells. We have shown that wettability-controlled by GO deposition-influences biocompatibilities and antibacterial effect of biomaterial surfaces. Discussion: Measuring the contact angle, it is found that contact angle for hydrophobic is increased to 150.590 and reduced to 11.580 by heat and argon plasma treatment, respectively, from 75.880 that was initially in the case of hydrophobic surface. XPS analysis confirmed various oxygen-containing functional groups transforming as deposited hydrophobic surface into superhydrophobic and hydrophilic surface. Thus, we have proposed a new, direct, cost-effective, and highly productive method for the synthesis of rGO and GO-with various surface properties-for biological applications. Similarly, for the dental implant application, the Streptococcus mutans was used as an antibacterial effect and found that S. mutans grows slowly on hydrophilic surface. Thus, antibacterial effect was prominent on GO with hydrophilic surface.


Assuntos
Atmosfera/química , Grafite/síntese química , Gases em Plasma/farmacologia , Animais , Morte Celular/efeitos dos fármacos , Linhagem Celular , Grafite/química , Camundongos , Viabilidade Microbiana/efeitos dos fármacos , Oxirredução , Streptococcus mutans/efeitos dos fármacos , Água , Molhabilidade
5.
Nature ; 584(7821): 479-483, 2020 08.
Artigo em Inglês | MEDLINE | ID: mdl-32788728

RESUMO

Lipopolysaccharide (LPS) resides in the outer membrane of Gram-negative bacteria where it is responsible for barrier function1,2. LPS can cause death as a result of septic shock, and its lipid A core is the target of polymyxin antibiotics3,4. Despite the clinical importance of polymyxins and the emergence of multidrug resistant strains5, our understanding of the bacterial factors that regulate LPS biogenesis is incomplete. Here we characterize the inner membrane protein PbgA and report that its depletion attenuates the virulence of Escherichia coli by reducing levels of LPS and outer membrane integrity. In contrast to previous claims that PbgA functions as a cardiolipin transporter6-9, our structural analyses and physiological studies identify a lipid A-binding motif along the periplasmic leaflet of the inner membrane. Synthetic PbgA-derived peptides selectively bind to LPS in vitro and inhibit the growth of diverse Gram-negative bacteria, including polymyxin-resistant strains. Proteomic, genetic and pharmacological experiments uncover a model in which direct periplasmic sensing of LPS by PbgA coordinates the biosynthesis of lipid A by regulating the stability of LpxC, a key cytoplasmic biosynthetic enzyme10-12. In summary, we find that PbgA has an unexpected but essential role in the regulation of LPS biogenesis, presents a new structural basis for the selective recognition of lipids, and provides opportunities for future antibiotic discovery.


Assuntos
Membrana Celular/química , Escherichia coli/química , Escherichia coli/patogenicidade , Lipopolissacarídeos/química , Lipopolissacarídeos/metabolismo , Amidoidrolases/química , Amidoidrolases/metabolismo , Motivos de Aminoácidos , Membrana Externa Bacteriana/química , Membrana Externa Bacteriana/metabolismo , Sítios de Ligação , Membrana Celular/metabolismo , Estabilidade Enzimática , Escherichia coli/citologia , Escherichia coli/efeitos dos fármacos , Genes Essenciais , Hidrolases/química , Hidrolases/metabolismo , Lipídeo A/química , Lipídeo A/metabolismo , Lipopolissacarídeos/biossíntese , Testes de Sensibilidade Microbiana , Viabilidade Microbiana/efeitos dos fármacos , Modelos Moleculares , Fragmentos de Peptídeos/química , Fragmentos de Peptídeos/metabolismo , Fragmentos de Peptídeos/farmacologia , Periplasma/química , Periplasma/metabolismo , Ligação Proteica , Virulência
6.
Nat Commun ; 11(1): 4157, 2020 08 19.
Artigo em Inglês | MEDLINE | ID: mdl-32814767

RESUMO

Swarming is a form of collective bacterial motion enabled by flagella on the surface of semi-solid media. Swarming populations exhibit non-genetic or adaptive resistance to antibiotics, despite sustaining considerable cell death. Here, we show that antibiotic-induced death of a sub-population benefits the swarm by enhancing adaptive resistance in the surviving cells. Killed cells release a resistance-enhancing factor that we identify as AcrA, a periplasmic component of RND efflux pumps. The released AcrA interacts on the surface of live cells with an outer membrane component of the efflux pump, TolC, stimulating drug efflux and inducing expression of other efflux pumps. This phenomenon, which we call 'necrosignaling', exists in other Gram-negative and Gram-positive bacteria and displays species-specificity. Given that adaptive resistance is a known incubator for evolving genetic resistance, our findings might be clinically relevant to the rise of multidrug resistance.


Assuntos
Antibacterianos/metabolismo , Bactérias/metabolismo , Proteínas de Bactérias/metabolismo , Resistência Microbiana a Medicamentos/fisiologia , Transdução de Sinais/fisiologia , Adaptação Fisiológica/fisiologia , Antibacterianos/farmacologia , Bactérias/classificação , Proteínas da Membrana Bacteriana Externa/metabolismo , Bactérias Gram-Negativas/classificação , Bactérias Gram-Negativas/metabolismo , Bactérias Gram-Positivas/classificação , Bactérias Gram-Positivas/metabolismo , Viabilidade Microbiana/efeitos dos fármacos , Periplasma/metabolismo , Especificidade da Espécie
7.
PLoS One ; 15(8): e0237223, 2020.
Artigo em Inglês | MEDLINE | ID: mdl-32810178

RESUMO

Bacillus anthracis, the bacteria that causes anthrax, a disease that primarily affects herbivorous animals, is a soil borne endospore-forming microbe. Environmental distribution of viable spores determines risky landscapes for herbivore exposure and subsequent anthrax outbreaks. Spore survival and longevity depends on suitable conditions in its environment. Anthrax is endemic in Queen Elizabeth Protected Area in western Uganda. Periodic historical outbreaks with significant wildlife losses date to 1950s, but B. anthracis ecological niche in the ecosystem is poorly understood. This study used the Maximum Entropy modeling algorithm method to predict suitable niche and environmental conditions that may support anthrax distribution and spore survival. Model inputs comprised 471 presence-only anthrax occurrence data from park management records of 1956-2010, and 11 predictor variables derived from the World Climatic and Africa Soil Grids online resources, selected considering the ecology of anthrax. The findings revealed predicted suitable niche favoring survival and distribution of anthrax spores as a narrow-restricted corridor within the study area, defined by hot-dry climatic conditions with alkaline soils rich in potassium and calcium. A mean test AUC of 0.94 and predicted probability of 0.93 for anthrax presence were registered. The five most important predictor variables that accounted for 93.8% of model variability were annual precipitation (70.1%), exchangeable potassium (12.6%), annual mean temperature (4.3%), soil pH (3.7%) and calcium (3.1%). The predicted suitable soil properties likely originate from existing sedimentary calcareous gypsum rocks. This has implications for long-term presence of B. anthracis spores and might explain the long history of anthrax experienced in the area. However, occurrence of suitable niche as a restricted hot zone offers opportunities for targeted anthrax surveillance, response and establishment of monitoring strategies in QEPA.


Assuntos
Antraz/microbiologia , Bacillus anthracis/fisiologia , Animais , Antraz/epidemiologia , Clima , Conservação dos Recursos Naturais , Surtos de Doenças , Ecossistema , Meio Ambiente , Humanos , Viabilidade Microbiana , Modelos Biológicos , Fatores de Risco , Solo/química , Microbiologia do Solo , Esporos Bacterianos/fisiologia , Uganda
8.
Food Chem ; 332: 127420, 2020 Dec 01.
Artigo em Inglês | MEDLINE | ID: mdl-32622191

RESUMO

The outbreaks of Cronobacter sakazakii, Salmonella spp, and Bacillus cereus in powdered foods have been increasing in worldwide. However, an effective method to pasteurize powdered foods before consumption remains lacking. A prototype Intense Pulsed Light (IPL) system was developed to disinfect powdered foods under different IPL and environmental conditions. Synergistic effect of IPL and TiO2 photocatalysis on microbial inactivation was studied. The results show that high energy intensity of each pulse, high peak intensity, and short pulsed duration contributed to a high microbe inactivation. With TiO2 photocatalysis, one additional log10 reduction was achieved, bringing the total log reduction to 4.71 ± 0.07 (C. sakazakii), 3.49 ± 0.01 (E. faecium), and 2.52 ± 0.10 (B. cereus) in non-fat dry milk, and 5.42 ± 0.10 (C. sakazakii), 4.95 ± 0.24 (E. faecium), 2.80 ± 0.23 (B. cereus) in wheat flour. IPL treatment combined with the TiO2 photocatalysis exhibits a strong potential to reduce the energy consumption in improving the safety of powdered foods.


Assuntos
Cronobacter sakazakii/efeitos da radiação , Cronobacter/efeitos da radiação , Farinha/microbiologia , Conservação de Alimentos/métodos , Viabilidade Microbiana/efeitos da radiação , Leite/microbiologia , Triticum/microbiologia , Animais , Bacillus cereus/crescimento & desenvolvimento , Bacillus cereus/efeitos da radiação , Cronobacter/crescimento & desenvolvimento , Microbiologia de Alimentos , Conservação de Alimentos/instrumentação , Luz , Pós/química , Salmonella/crescimento & desenvolvimento , Salmonella/efeitos da radiação
9.
Proc Natl Acad Sci U S A ; 117(32): 19455-19464, 2020 08 11.
Artigo em Inglês | MEDLINE | ID: mdl-32703812

RESUMO

A better understanding of how antibiotic exposure impacts the evolution of resistance in bacterial populations is crucial for designing more sustainable treatment strategies. The conventional approach to this question is to measure the range of concentrations over which resistant strain(s) are selectively favored over a sensitive strain. Here, we instead investigate how antibiotic concentration impacts the initial establishment of resistance from single cells, mimicking the clonal expansion of a resistant lineage following mutation or horizontal gene transfer. Using two Pseudomonas aeruginosa strains carrying resistance plasmids, we show that single resistant cells have <5% probability of detectable outgrowth at antibiotic concentrations as low as one-eighth of the resistant strain's minimum inhibitory concentration (MIC). This low probability of establishment is due to detrimental effects of antibiotics on resistant cells, coupled with the inherently stochastic nature of cell division and death on the single-cell level, which leads to loss of many nascent resistant lineages. Our findings suggest that moderate doses of antibiotics, well below the MIC of resistant strains, may effectively restrict de novo emergence of resistance even though they cannot clear already-large resistant populations.


Assuntos
Antibacterianos/farmacologia , Farmacorresistência Bacteriana/efeitos dos fármacos , Pseudomonas aeruginosa/efeitos dos fármacos , Relação Dose-Resposta a Droga , Farmacorresistência Bacteriana/genética , Testes de Sensibilidade Microbiana , Viabilidade Microbiana/efeitos dos fármacos , Modelos Teóricos , Plasmídeos/genética , Pseudomonas aeruginosa/genética , Pseudomonas aeruginosa/crescimento & desenvolvimento , Análise de Célula Única , Processos Estocásticos
10.
J Infect Dis ; 222(5): 719-721, 2020 08 04.
Artigo em Inglês | MEDLINE | ID: mdl-32609334

RESUMO

This manuscript explores the question of the seasonality of severe acute respiratory syndrome coronavirus 2 by reviewing 4 lines of evidence related to viral viability, transmission, ecological patterns, and observed epidemiology of coronavirus disease 2019 in the Southern Hemispheres' summer and early fall.


Assuntos
Infecções por Coronavirus/epidemiologia , Pandemias , Pneumonia Viral/epidemiologia , Betacoronavirus/isolamento & purificação , Betacoronavirus/fisiologia , Infecções por Coronavirus/virologia , Humanos , Viabilidade Microbiana , Pneumonia Viral/virologia , Estações do Ano , Temperatura
11.
PLoS One ; 15(7): e0236059, 2020.
Artigo em Inglês | MEDLINE | ID: mdl-32716948

RESUMO

Most cosmetic products are susceptible to microbiological spoilage due to contaminations that could happen during fabrication or by consumer's repetitive manipulation. The composition of cosmetic products must guarantee efficient bacterial inactivation all along with the product shelf life, which is usually assessed by challenge-tests. A challenge-test consists in inoculating specific bacteria, i.e. Staphylococcus aureus, in the formula and then investigating the bacterial log reduction over time. The main limitation of this method is relative to the time-consuming protocol, where 30 days are needed to obtain results. In this study, we have proposed a rapid alternative method coupling High Content Screening-Confocal Laser Scanning Microscopy (HCS-CLSM), image analysis and modeling. It consists in acquiring real-time S. aureus inactivation kinetics on short-time periods (typically 4h) and in predicting the efficiency of preservatives on longer scale periods (up to 7 days). The action of two preservatives, chlorphenesin and benzyl alcohol, was evaluated against S. aureus at several concentrations in a cosmetic matrix. From these datasets, we compared two secondary models to determine the logarithm reduction time (Dc) for each preservative concentration. Afterwards, we used two primary inactivation models to predict log reductions for up to 7 days and we compared them to observed log reductions. The IQ model better fits datasets and the Q value gives information about the matrix level of interference.


Assuntos
Cosméticos/química , Microscopia Confocal , Conservantes Farmacêuticos/farmacologia , Staphylococcus aureus/efeitos dos fármacos , Cinética , Testes de Sensibilidade Microbiana , Viabilidade Microbiana/efeitos dos fármacos , Staphylococcus aureus/fisiologia , Fatores de Tempo
12.
PLoS One ; 15(7): e0236185, 2020.
Artigo em Inglês | MEDLINE | ID: mdl-32730344

RESUMO

Fluorescent markers are a powerful tool and have been widely applied in biology for different purposes. The genome sequence of Xanthomonas citri subsp. citri (X. citri) revealed that approximately 30% of the genes encoded hypothetical proteins, some of which could play an important role in the success of plant-pathogen interaction and disease triggering. Therefore, revealing their functions is an important strategy to understand the bacterium pathways and mechanisms involved in plant-host interaction. The elucidation of protein function is not a trivial task, but the identification of the subcellular localization of a protein is key to understanding its function. We have constructed an integrative vector, pMAJIIc, under the control of the arabinose promoter, which allows the inducible expression of red fluorescent protein (mCherry) fusions in X. citri, suitable for subcellular localization of target proteins. Fluorescence microscopy was used to track the localization of VrpA protein, which was visualized surrounding the bacterial outer membrane, and the GyrB protein, which showed a diffused cytoplasmic localization, sometimes with dots accumulated near the cellular poles. The integration of the vector into the amy locus of X. citri did not affect bacterial virulence. The vector could be stably maintained in X. citri, and the disruption of the α-amylase gene provided an ease screening method for the selection of the transformant colonies. The results demonstrate that the mCherry-containing vector here described is a powerful tool for bacterial protein localization in cytoplasmic and periplasmic environments.


Assuntos
Proteínas de Bactérias/metabolismo , Citoplasma/metabolismo , Periplasma/metabolismo , Proteínas Recombinantes de Fusão/metabolismo , Xanthomonas/metabolismo , Arabinose/farmacologia , Cromossomos Bacterianos/genética , Vetores Genéticos/metabolismo , Viabilidade Microbiana/efeitos dos fármacos , Transporte Proteico/efeitos dos fármacos , Amido/metabolismo , Frações Subcelulares/efeitos dos fármacos , Xanthomonas/patogenicidade
13.
Proc Natl Acad Sci U S A ; 117(31): 18729-18736, 2020 08 04.
Artigo em Inglês | MEDLINE | ID: mdl-32669426

RESUMO

Many microorganisms face a fundamental trade-off between reproduction and survival: Rapid growth boosts population size but makes microorganisms sensitive to external stressors. Here, we show that starved bacteria encountering new resources can break this trade-off by evolving phenotypic heterogeneity in lag time. We quantify the distribution of single-cell lag times of populations of starved Escherichia coli and show that population growth after starvation is primarily determined by the cells with shortest lag due to the exponential nature of bacterial population dynamics. As a consequence, cells with long lag times have no substantial effect on population growth resumption. However, we observe that these cells provide tolerance to stressors such as antibiotics. This allows an isogenic population to break the trade-off between reproduction and survival. We support this argument with an evolutionary model which shows that bacteria evolve wide lag time distributions when both rapid growth resumption and survival under stressful conditions are under selection. Our results can explain the prevalence of antibiotic tolerance by lag and demonstrate that the benefits of phenotypic heterogeneity in fluctuating environments are particularly high when minorities with extreme phenotypes dominate population dynamics.


Assuntos
Farmacorresistência Bacteriana , Escherichia coli , Viabilidade Microbiana , Antibacterianos/farmacologia , Evolução Biológica , Escherichia coli/genética , Escherichia coli/fisiologia , Modelos Biológicos , Fenótipo , Análise de Célula Única
14.
Proc Natl Acad Sci U S A ; 117(30): 18010-18017, 2020 07 28.
Artigo em Inglês | MEDLINE | ID: mdl-32665440

RESUMO

Mutant phenotype analysis of bacteria has been revolutionized by genome-scale screening procedures, but essential genes have been left out of such studies because mutants are missing from the libraries analyzed. Since essential genes control the most fundamental processes of bacterial life, this is a glaring deficiency. To address this limitation, we developed a procedure for transposon insertion mutant sequencing that includes essential genes. The method, called transformation transposon insertion mutant sequencing (TFNseq), employs saturation-level libraries of bacterial mutants generated by natural transformation with chromosomal DNA mutagenized heavily by in vitro transposition. The efficient mutagenesis makes it possible to detect large numbers of insertions in essential genes immediately after transformation and to follow their loss during subsequent growth. It was possible to order 45 essential processes based on how rapidly their inactivation inhibited growth. Inactivating ATP production, deoxyribonucleotide synthesis, or ribosome production blocked growth the fastest, whereas inactivating cell division or outer membrane protein synthesis blocked it the slowest. Individual mutants deleted of essential loci formed microcolonies of nongrowing cells whose sizes were generally consistent with the TFNseq ordering. The sensitivity of essential functions to genetic inactivation provides a metric for ranking their relative importance for bacterial replication and growth. Highly sensitive functions could represent attractive antibiotic targets since even partial inhibition should reduce growth.


Assuntos
Fenômenos Fisiológicos Bacterianos , Genes Bacterianos , Genes Essenciais , Viabilidade Microbiana/genética , Mutação , Taxa de Mutação , Deleção de Sequência
15.
Z Naturforsch C J Biosci ; 75(9-10): 363-367, 2020 Sep 25.
Artigo em Inglês | MEDLINE | ID: mdl-32623382

RESUMO

The world is facing, while writing this review, a global pandemic due to one of the types of the coronaviruses (i.e., COVID-19), which is a new virus. Among the most important reasons for the transmission of infection between humans is the presence of this virus active on the surfaces and materials. Here, we addressed important questions such as do coronaviruses remain active on the inanimate surfaces? Do the types of inanimate surfaces affect the activity of coronaviruses? What are the most suitable ingredients that used to inactivate viruses? This review article addressed many of the works that were done in the previous periods on the survival of many viruses from the coronaviruses family on various surfaces such as steel, glass, plastic, Teflon, ceramic tiles, silicon rubber and stainless steel copper alloys, Al surface, sterile sponges, surgical gloves and sterile latex. The impacts of environmental conditions such as temperature and humidity were presented and discussed. The most important active ingredients that can deactivate viruses on the surfaces were reported here. We hope that these active ingredients will have the same effect on COVID-19.


Assuntos
Infecções por Coronavirus/transmissão , Coronavirus/fisiologia , Fômites/virologia , Pneumonia Viral/transmissão , Desinfecção/métodos , Humanos , Viabilidade Microbiana , Pandemias
16.
J Hosp Infect ; 106(2): 226-231, 2020 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-32652214

RESUMO

BACKGROUND: In late 2019, a novel human coronavirus - severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) - emerged in Wuhan, China. This virus has caused a global pandemic involving more than 200 countries. SARS-CoV-2 is highly adapted to humans and readily transmits from person-to-person. AIM: To investigate the infectivity of SARS-CoV-2 under various environmental and pH conditions. The efficacies of various laboratory virus inactivation methods and home disinfectants against SARS-CoV-2 were investigated. METHODS: The residual virus in dried form or in solution was titrated on to Vero E6 cells on days 0, 1, 3, 5 and 7 after incubation at different temperatures. Viral viability was determined after treatment with various disinfectants and pH solutions at room temperature (20-25oC). FINDINGS: SARS-CoV-2 was able to retain viability for 3-5 days in dried form or 7 days in solution at room temperature. SARS-CoV-2 could be detected under a wide range of pH conditions from pH 4 to pH 11 for several days, and for 1-2 days in stool at room temperature but lost 5 logs of infectivity. A variety of commonly used disinfectants and laboratory inactivation procedures were found to reduce viral viability effectively. CONCLUSION: This study demonstrated the stability of SARS-CoV-2 on environmental surfaces, and raises the possibility of faecal-oral transmission. Commonly used fixatives, nucleic acid extraction methods and heat inactivation were found to reduce viral infectivity significantly, which could ensure hospital and laboratory safety during the SARS-CoV-2 pandemic.


Assuntos
Betacoronavirus/crescimento & desenvolvimento , Betacoronavirus/patogenicidade , Infecções por Coronavirus/fisiopatologia , Viabilidade Microbiana , Pneumonia Viral/fisiopatologia , Síndrome Respiratória Aguda Grave/patologia , Virulência , Inativação de Vírus , China/epidemiologia , Infecções por Coronavirus/epidemiologia , Humanos , Pandemias , Pneumonia Viral/epidemiologia , Síndrome Respiratória Aguda Grave/epidemiologia
17.
Int J Food Microbiol ; 329: 108665, 2020 Sep 16.
Artigo em Inglês | MEDLINE | ID: mdl-32497789

RESUMO

Simultaneous treatment with 222-nm KrCl excilamp and mild heating (EX-MH) at 45, 50 and 55 °C showed synergistic bactericidal effects on non-acid and acid adapted cells of Escherichia coli O157:H7 and Salmonella Typhimurium in apple juice. In particular, acid-adapted pathogens exhibited increased resistance to EX-MH compared to pathogenic bacteria that were not acid-adapted. Also, elucidation of the synergistic bactericidal mechanism of EX-MH was performed through several assays and this mechanism was described as follows: (i) when KrCl excilamp (EX) and mild heating (MH) are applied simultaneously, MH reversibly inactivates the antioxidant enzyme, superoxide dismutase (SOD), thereby increasing accumulation of reactive oxygen species (ROS) generated by EX and thus inducing synergistic ROS generation, (ii) ROS production induces lipid peroxidation occurrence in the cell membrane, (iii) this lipid peroxidation occurrence in the cell membrane induces synergistic destruction of cell membrane, resulting in synergistic cell death. While EX-MH of 45, 50, or 55 °C reduced E. coli O157:H7 (the pathogen most resistant to EX-MH) in apple juice by 5-log, the qualities such as color (L*, a*, and b*), total phenolic compounds (TPC), and DPPH free radical scavenging activity of apple juice did not change significantly (P > 0.05). This study not only suggests the applicability of EX-MH to the apple juice industry, but also can be used as baseline data for future relevant research.


Assuntos
Antibacterianos/farmacologia , Escherichia coli O157/efeitos dos fármacos , Microbiologia de Alimentos/métodos , Sucos de Frutas e Vegetais/microbiologia , Calefação , Viabilidade Microbiana , Salmonella typhimurium/efeitos dos fármacos , Bebidas/microbiologia , Cloro/farmacologia , Contagem de Colônia Microbiana , Criptônio/química , Criptônio/farmacologia , Malus/microbiologia
18.
Environ Sci Pollut Res Int ; 27(26): 32796-32808, 2020 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-32519106

RESUMO

To understand the characteristics of bacterial viability and diversity in landscape waters replenished with reclaimed water, the typical landscape lake using reclaimed water was investigated in this study. Samples were collected from a reclaimed water inlet (P1), a reclaimed water distribution outlet (P2), and a landscape lake replenished by reclaimed water (P3). By means of measuring adenosine triphosphate (ATP), flow cytometry (FCM), and 16S rRNA gene high-throughput sequencing, the bacterial viability and diversity in reclaimed water distribution system and landscape lake were illustrated. The bacterial ATP contents at P1, P2, and P3 were 3.55 ± 1.79 ng/L, 3.31 ± 1.43 ng/L, and 18.97 ± 6.39 µg/L, and the intact bacterial cell concentrations were 5.91 ± 0.52 × 104 cells/mL, 7.95 ± 2.58 × 104 cells/mL, and 5.65 ± 2.10 × 106 cells/mL, respectively. These results indicated a significant increase of bacterial viability in the landscape lake. The Shannon diversity index of 6.535, 7.05, and 6.886 at P1, P2, and P3, respectively, demonstrated no notable change of bacterial diversity from reclaimed water distribution system to landscape lake. However, the relative abundance of Pseudomonas sp. at P3 was significantly higher than that at P1. These findings indicated that viable but non-culturable (VBNC) bacteria could be revived in the landscape lake. The bacterial viability during reclaimed water reuse should deserve special attention.


Assuntos
Bactérias/genética , Lagos , China , Viabilidade Microbiana , RNA Ribossômico 16S
19.
Nature ; 582(7810): 119-123, 2020 06.
Artigo em Inglês | MEDLINE | ID: mdl-32494069

RESUMO

The three-dimensional architecture of the genome governs its maintenance, expression and transmission. The cohesin protein complex organizes the genome by topologically linking distant loci, and is highly enriched in specialized chromosomal domains surrounding centromeres, called pericentromeres1-6. Here we report the three-dimensional structure of pericentromeres in budding yeast (Saccharomyces cerevisiae) and establish the relationship between genome organization and function. We find that convergent genes mark pericentromere borders and, together with core centromeres, define their structure and function by positioning cohesin. Centromeres load cohesin, and convergent genes at pericentromere borders trap it. Each side of the pericentromere is organized into a looped conformation, with border convergent genes at the base. Microtubule attachment extends a single pericentromere loop, size-limited by convergent genes at its borders. Reorienting genes at borders into a tandem configuration repositions cohesin, enlarges the pericentromere and impairs chromosome biorientation during mitosis. Thus, the linear arrangement of transcriptional units together with targeted cohesin loading shapes pericentromeres into a structure that is competent for chromosome segregation. Our results reveal the architecture of the chromosomal region within which kinetochores are embedded, as well as the restructuring caused by microtubule attachment. Furthermore, we establish a direct, causal relationship between the three-dimensional genome organization of a specific chromosomal domain and cellular function.


Assuntos
Centrômero/genética , Centrômero/metabolismo , Genes Fúngicos , Saccharomyces cerevisiae/citologia , Saccharomyces cerevisiae/genética , Proteínas de Ciclo Celular/metabolismo , Centrômero/química , Proteínas Cromossômicas não Histona/metabolismo , Segregação de Cromossomos , Genoma Fúngico/genética , Viabilidade Microbiana/genética , Mitose/genética , Conformação Molecular
20.
PLoS Negl Trop Dis ; 14(6): e0008387, 2020 06.
Artigo em Inglês | MEDLINE | ID: mdl-32574158

RESUMO

Environmental enteric dysfunction (EED) is characterized by diffuse villous atrophy of the small bowel. EED is strongly associated with stunting, a major public health problem linked to increased childhood morbidity and mortality. EED and subsequent stunting of linear growth are surmised to have microbial origins. To interrogate this relationship, we defined the comprehensive virome (eukaryotic virus and bacteriophage) and bacterial microbiome of a longitudinal cohort of rural Malawian children with extensive metadata and intestinal permeability testing at each time point. We found thirty bacterial taxa differentially associated with linear growth. We detected many eukaryotic viruses. Neither the total number of eukaryotic families nor a specific viral family was statistically associated with improved linear growth. We identified 3 differentially abundant bacteriophage among growth velocities. Interestingly, there was a positive correlation between bacteria and bacteriophage richness in children with subsequent adequate/moderate growth which children with subsequent poor growth lacked. This suggests that a disruption in the equilibrium between bacteria and bacteriophage communities might be associated with subsequent poor growth. Future studies of EED and stunting should include the evaluation of viral communities in addition to bacterial microbiota to understand the complete microbial ecology of these poorly understood entities.


Assuntos
Bactérias/classificação , Bacteriófagos/classificação , Microbioma Gastrointestinal , Trato Gastrointestinal/microbiologia , Trato Gastrointestinal/virologia , Transtornos do Crescimento/microbiologia , Transtornos do Crescimento/virologia , Bactérias/genética , Bactérias/isolamento & purificação , Bactérias/virologia , Bacteriófagos/genética , Bacteriófagos/crescimento & desenvolvimento , Bacteriófagos/isolamento & purificação , Pré-Escolar , Feminino , Gastroenteropatias/microbiologia , Gastroenteropatias/virologia , Humanos , Lactente , Intestino Delgado/microbiologia , Intestino Delgado/virologia , Malaui , Masculino , Viabilidade Microbiana , Permeabilidade , RNA Ribossômico 16S
SELEÇÃO DE REFERÊNCIAS
DETALHE DA PESQUISA