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1.
BMC Oral Health ; 21(1): 460, 2021 09 22.
Artigo em Inglês | MEDLINE | ID: mdl-34551743

RESUMO

BACKGROUND: Oral microbiome played an important role in maintaining healthy state and might exhibit certain changes under circumstances of diseases. However, current microbiological research using sequencing techniques did not regard dead bacteria as a separate part, causing findings based on subsequent analyses on dynamic equilibrium and functional pathways of microbes somewhat questionable. Since treatment by propidium monoazide (PMA) was able to remove dead bacteria effectively, it would be worth studying how the sequencing results after PMA treatment differed from those focusing on the whole microbiota. METHODS: Unstimulated whole saliva samples were obtained from 18 healthy people from 3 age groups (children, adults, and the elderly). After removal of dead bacteria by propidium monoazide (PMA), changes in the profile of salivary microbiome were detected using 16S rRNA sequencing technology, and differences among age groups were compared subsequently. RESULTS: Dead bacteria accounted for nearly a half of the whole bacteria flora in saliva, while freezing had little effect on the proportion of deaths. After treatment with PMA, the numbers of OTUs reduced by 4.4-14.2%, while the Shannon diversity indices decreased significantly (P < 0.01). Only 35.2% of positive and 6.1% of negative correlations were found to be shared by the whole microbiota and that with dead bacteria removed. Differences in significantly changed OTUs and functional pathways among different age groups were also observed between the group of PMA and the control. CONCLUSIONS: It was necessary to take the influence of living state of bacteria into account in analytic studies of salivary microbiome.


Assuntos
Microbiota , Idoso , Azidas , Bactérias/genética , Criança , DNA Bacteriano/genética , Humanos , Viabilidade Microbiana , Propídio/análogos & derivados , RNA Ribossômico 16S/genética
2.
Int J Food Microbiol ; 357: 109381, 2021 Nov 02.
Artigo em Inglês | MEDLINE | ID: mdl-34492585

RESUMO

Viable but nonculturable (VBNC) state of microorganisms has attracted much attention due to its characteristics, including the difficulty in detection by culture-based methods, virulence retention, high resistance, and so on. As a foodborne pathogen, Staphylococcus aureus is widely distributed, and has been found to enter the VBNC state under some environmental stresses, posing a potential threat to human health. Freezing is a common condition for food storage. This study investigated whether citric acid, a common food additive, could induce S. aureus into the VBNC state at -20 °C. By measuring the number of culturable and viable cells, it was found that S. aureus entered the VBNC state after 72 days of induction in citric acid buffer at -20 °C. The VBNC cells were then successfully resuscitated at 37 °C in trypsin soybean medium (TSB) with or without heat shock treatment, and TSB supplemented with sodium pyruvate and Tween 80 after 48 h. Heat shock resulted in an excellent resuscitation effect. Observed by transmission electron microscopy, the internal structure of VBNC cells was found markedly changed, compared with that of exponential phase cells. API ZYM kit was used to compare the intracellular enzyme activity of S. aureus in the exponential phase with that in the VBNC state. The results showed that the enzyme activity decreased significantly in VBNC cells, and that the VBNC cells were more resistant to simulated gastrointestinal fluid through flow cytometry analysis. Quantitative reverse-transcription polymerase chain reaction results suggested that the ability of adhesion and biofilm formation of VBNC cells might be decreased due to the down-regulation of related genes. However, it should not be ignored the recovery potential of biofilm-forming ability of VBNC cells caused by the high expression of sarA. In conclusion, S. aureus could be induced into the VBNC state in citric acid buffer at -20 °C, which showed changes in some biological characteristics and could resuscitate successfully by many conditions. Food industry needs to pay attention to the potential hazard by VBNC S. aureus under frozen conditions.


Assuntos
Biofilmes , Staphylococcus aureus , Meios de Cultura , Congelamento , Humanos , Viabilidade Microbiana , Estresse Fisiológico
3.
Elife ; 102021 09 10.
Artigo em Inglês | MEDLINE | ID: mdl-34505573

RESUMO

Myxococcus xanthus, a soil bacterium, predates collectively using motility to invade prey colonies. Prey lysis is mostly thought to rely on secreted factors, cocktails of antibiotics and enzymes, and direct contact with Myxococcus cells. In this study, we show that on surfaces the coupling of A-motility and contact-dependent killing is the central predatory mechanism driving effective prey colony invasion and consumption. At the molecular level, contact-dependent killing involves a newly discovered type IV filament-like machinery (Kil) that both promotes motility arrest and prey cell plasmolysis. In this process, Kil proteins assemble at the predator-prey contact site, suggesting that they allow tight contact with prey cells for their intoxication. Kil-like systems form a new class of Tad-like machineries in predatory bacteria, suggesting a conserved function in predator-prey interactions. This study further reveals a novel cell-cell interaction function for bacterial pili-like assemblages.


Assuntos
Proteínas de Bactérias/metabolismo , Escherichia coli/crescimento & desenvolvimento , Fímbrias Bacterianas/metabolismo , Myxococcus xanthus/metabolismo , Microbiologia do Solo , Proteínas de Bactérias/genética , Fímbrias Bacterianas/genética , Viabilidade Microbiana , Movimento , Myxococcus xanthus/genética , Myxococcus xanthus/patogenicidade , Análise de Célula Única , Fatores de Tempo
4.
Food Res Int ; 148: 110625, 2021 10.
Artigo em Inglês | MEDLINE | ID: mdl-34507769

RESUMO

The inactivation of pathogenic microorganisms in water and high transmittance liquid foods has been studied extensively. The efficiency of the process is relatively low for treating opaque liquid foods using traditional UV systems. This study evaluated the ability of UV-C light to inactivate foodborne pathogens in a simulated opaque fluid (6.5 to 17 cm-1) at commercial relevant flow rates (31.70, 63.40, 95.10 gph) using a pilot-scale Dean Flow UV system. In this study, a mathematical model for the prediction of delivered fluence was developed by the biodosimetry method. The results revealed that increased Reduction equivalent fluence (REF) rates were observed with increased flow rates due to additional turbulence. The experimental and calculated REF were well correlated with the UV-C absorption coefficient range of 6.5 to 17 cm-1 indicating efficient mixing in the reactor. REF scaled up linearly at experimental conditions as an inverse function of flow rate and absorption coefficient, and a linear mathematical model (R2 > 0.99, p < 0.05) to predict delivered REF was developed. The model was tested and validated against independent experiments using Salmonella Typhimurium and Bacillus cereus endospores. The predicted and experimental REF values were in close agreement (p > 0.05). It is demonstrated that the developed model can predict the REF, thus microbial inactivation of microbial suspensions in simulated fluid with the absorption coefficient of 6.5-17 cm-1 and flow rates of 31.70-95.10 gph. The pilot system will be field-tested against microorganisms in highly absorbing and scattering fluids.


Assuntos
Esporos Bacterianos , Raios Ultravioleta , Bacillus cereus , Viabilidade Microbiana , Salmonella typhimurium
5.
ACS Appl Mater Interfaces ; 13(33): 39957-39966, 2021 Aug 25.
Artigo em Inglês | MEDLINE | ID: mdl-34376049

RESUMO

Microbial inoculants can enhance soil quality, promote plant nutrient acquisition, and alleviate problems caused by the excessive use of chemical fertilizers. However, susceptibility to harsh conditions during transport and storage, as well as the short shelf-life of plant growth-promoting rhizobacteria (PGPR), limit industrial application. Herein, a novel strategy to form nanocoating on bacterial surfaces to enhance viability was proposed. The nanocoating was composed of N-hydroxysuccinimide (NHS)-modified poly (γ-glutamic acid) (γ-PGA) and calcium ions, which could adhere to the surface of bacteria by forming covalent bonds and ionic bonds with the bacteria. The bacteria encapsulated in the coating had better resistance against harsh conditions than bare bacteria. The viability of coated bacteria was also increased by 2.38 times compared with bare bacteria after 4 weeks of storage. The pot experiment showed that coated Pseudomonas stutzeri NRCB010 had better growth-promoting properties compared with free P. stutzeri NRCB010. These results indicate that cell surface engineering is an effective method to enhance the resistance of bacteria against harsh conditions and is expected to promote the widespread use of PGPR.


Assuntos
Materiais Revestidos Biocompatíveis/química , Materiais Revestidos Biocompatíveis/metabolismo , Nanoestruturas/química , Ácido Poliglutâmico/análogos & derivados , Pseudomonas stutzeri/metabolismo , Biotecnologia , Proliferação de Células/efeitos dos fármacos , Fertilizantes/microbiologia , Temperatura Alta , Engenharia Metabólica , Viabilidade Microbiana/efeitos dos fármacos , Desenvolvimento Vegetal/efeitos dos fármacos , Ácido Poliglutâmico/química , Ácido Poliglutâmico/metabolismo , Pseudomonas stutzeri/efeitos dos fármacos , Exposição à Radiação , Solo , Estresse Mecânico
6.
Nucleic Acids Res ; 49(15): 8757-8776, 2021 09 07.
Artigo em Inglês | MEDLINE | ID: mdl-34379789

RESUMO

As compared to eukaryotes, bacteria have a reduced tRNA gene set encoding between 30 and 220 tRNAs. Although in most bacterial phyla tRNA genes are dispersed in the genome, many species from distinct phyla also show genes forming arrays. Here, we show that two types of arrays with distinct evolutionary origins exist. This work focuses on long tRNA gene arrays (L-arrays) that encompass up to 43 genes, which disseminate by horizontal gene transfer and contribute supernumerary tRNA genes to the host. Although in the few cases previously studied these arrays were reported to be poorly transcribed, here we show that the L-array of the model cyanobacterium Anabaena sp. PCC 7120, encoding 23 functional tRNAs, is largely induced upon impairment of the translation machinery. The cellular response to this challenge involves a global reprogramming of the transcriptome in two phases. tRNAs encoded in the array are induced in the second phase of the response, directly contributing to cell survival. Results presented here show that in some bacteria the tRNA gene set may be partitioned between a housekeeping subset, which constantly sustains translation, and an inducible subset that is generally silent but can provide functionality under particular conditions.


Assuntos
Genes Bacterianos , Óperon , Biossíntese de Proteínas , RNA de Transferência/genética , Estresse Fisiológico/genética , Anabaena/genética , Antibacterianos/farmacologia , Regulação Bacteriana da Expressão Gênica , Genoma Bacteriano , Viabilidade Microbiana/genética , RNA de Transferência/metabolismo , Sequências Reguladoras de Ácido Nucleico
7.
Front Cell Infect Microbiol ; 11: 716592, 2021.
Artigo em Inglês | MEDLINE | ID: mdl-34368019

RESUMO

Bacteria modify their morphology in response to various factors including growth stage, nutrient availability, predation, motility and long-term survival strategies. Morphological changes may also be associated with specific physiological phenotypes such as the formation of dormant or persister cells in a "viable but non-culturable" (VBNC) state which frequently display different shapes and size compared to their active counterparts. Such dormancy phenotypes can display various degrees of tolerance to antibiotics and therefore a detailed understanding of these phenotypes is crucial for combatting chronic infections and associated diseases. Cell shape and size are therefore more than simple phenotypic characteristics; they are important physiological properties for understanding bacterial life-strategies and pathologies. However, quantitative studies on the changes to cell morphologies during bacterial growth, persister cell formation and the VBNC state are few and severely constrained by current limitations in the most used investigative techniques of flow cytometry (FC) and light or electron microscopy. In this study, we applied high-throughput Imaging Flow Cytometry (IFC) to characterise and quantify, at single-cell level and over time, the phenotypic heterogeneity and morphological changes in cultured populations of four bacterial species, Bacillus subtilis, Lactiplantibacillus plantarum, Pediococcus acidilactici and Escherichia coli. Morphologies in relation to growth stage and stress responses, cell integrity and metabolic activity were analysed. Additionally, we were able to identify and morphologically classify dormant cell phenotypes such as VBNC cells and monitor the resuscitation of persister cells in Escherichia coli following antibiotic treatment. We therefore demonstrate that IFC, with its high-throughput data collection and image capture capabilities, provides a platform by which a detailed understanding of changes in bacterial phenotypes and their physiological implications may be accurately monitored and quantified, leading to a better understanding of the role of phenotypic heterogeneity in the dynamic microbiome.


Assuntos
Bactérias , Escherichia coli , Escherichia coli/genética , Citometria de Fluxo , Viabilidade Microbiana , Fenótipo
8.
J Photochem Photobiol B ; 222: 112277, 2021 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-34364078

RESUMO

The elimination of bacterial pathogens from water using ultraviolet C light-emitting diodes (UVC-LEDs) is a critical technology in terms of hygiene and sanitation. This technology has several advantages, such as low energy consumption, no heating requirements, and high effectiveness. Although several studies have reported the bactericidal effect of UVC-LEDs, little information is available on their bactericidal effect on water reservoirs contaminated with microorganisms. Therefore, the aim of this study was to optimize the bactericidal effects of UVC-LED irradiation, particularly at a wavelength of 278 nm, against major foodborne gram-positive and gram-negative pathogenic bacteria, such as Escherichia coli, Staphylococcus aureus, Bacillus cereus, Salmonella Typhimurium, and Listeria monocytogenes. The efficiency of the bactericidal effect of UVC-LED irradiation was determined based on three variables: exposure time (A, 0-60 min), stirring speed (B, 0-100 rpm), and volume of water (C, 400-1200 mL). To optimize the conditions, the operation of the designed model and results analysis were carried out using Box-Behnken design (BBD) and response surface method (RSM). The final conditions optimized for an effective bactericidal activity included a 60 min exposure time, a 100 rpm stirring speed, and 400 mL of liquid volume. Furthermore, the validation of the optimized model using the predicted values was calculated by the program, which was conducted by matching the actual values within standard deviations. The present study revealed that the optimization of a UVC-LED irradiation model is a promising approach for effectively controlling the contamination of water reservoirs by bacterial pathogens.


Assuntos
Bactérias Gram-Negativas/efeitos da radiação , Bactérias Gram-Positivas/efeitos da radiação , Raios Ultravioleta , Testes de Sensibilidade Microbiana , Viabilidade Microbiana/efeitos da radiação , Microbiologia da Água
9.
Food Res Int ; 147: 110528, 2021 09.
Artigo em Inglês | MEDLINE | ID: mdl-34399506

RESUMO

Lactobacillus spp. are known to accumulate large amounts of inorganic manganese, which protects against oxidative damage by scavenging free radicals. The ability of probiotic L. paracasei ATCC 55544 to maintain viability during long-term ambient storage may be enhanced by this microorganism's ability to accumulate manganese, which may act as a free radical scavenger. To investigate this hypothesis, X-ray fluorescence microscopy (XFM) was employed to determine the changes in the elemental composition of L. paracasei during growth in the MRS medium with or without added manganese. Moreover, manganese uptake by cells as a function of physiological growth state, early log vs. stationary phase was evaluated. The semiquantitative X-ray fluorescence microscopy results revealed that lower levels of manganese accumulation occurred during the early log phase of bacterial growth of L. paracasei cells (0.0064 µg/cm2) compared with the stationary phase cells (0.1355 µg/cm2). L. paracasei cells grown in manganese deficient MRS medium resulted in lower manganese uptake by cells (0.0027 µg/cm2). The L. paracasei cells were further embedded in milk powder matrix using a fluidized-bed drying technique and stored at a water activity (aw) of 0.33 at 25 °C for 15 days. The viability counts of L. paracasei cells grown in MRS medium harvested after 18 h growth and embedded in milk powder matrix retained viability of (9.19 ± 0.12 log CFU/g). No viable L. paracasei cells were observed in the case of embedded L. paracasei cells grown in manganese-deficient MRS medium harvested after 18 h growth or in the case of L. paracasei cells harvested after 4 h when grown in MRS medium. The lower level of manganese accumulation was found to be related to the loss of bacterial viability during storage.


Assuntos
Lactobacillus paracasei , Probióticos , Manganês , Viabilidade Microbiana , Microscopia de Fluorescência , Síncrotrons , Raios X
10.
Molecules ; 26(16)2021 Aug 16.
Artigo em Inglês | MEDLINE | ID: mdl-34443542

RESUMO

Biofilm infections are a global public health threat, necessitating new treatment strategies. Biofilm formation also contributes to the development and spread of multidrug-resistant (MDR) bacterial strains. Biofilm-associated chronic infections typically involve colonization by more than one bacterial species. The co-existence of multiple species of bacteria in biofilms exacerbates therapeutic challenges and can render traditional antibiotics ineffective. Polymeric nanoparticles offer alternative antimicrobial approaches to antibiotics, owing to their tunable physico-chemical properties. Here, we report the efficacy of poly(oxanorborneneimide) (PONI)-based antimicrobial polymeric nanoparticles (PNPs) against multi-species bacterial biofilms. PNPs showed good dual-species biofilm penetration profiles as confirmed by confocal laser scanning microscopy. Broad-spectrum antimicrobial activity was observed, with reduction in both bacterial viability and overall biofilm mass. Further, PNPs displayed minimal fibroblast toxicity and high antimicrobial activity in an in vitro co-culture model comprising fibroblast cells and dual-species biofilms of Escherichia coli and Pseudomonas aeruginosa. This study highlights a potential clinical application of the presented polymeric platform.


Assuntos
Bactérias/metabolismo , Biofilmes/efeitos dos fármacos , Nanopartículas/química , Polímeros/farmacologia , Células 3T3 , Animais , Biomassa , Sobrevivência Celular/efeitos dos fármacos , Fibroblastos/citologia , Fibroblastos/efeitos dos fármacos , Camundongos , Testes de Sensibilidade Microbiana , Viabilidade Microbiana/efeitos dos fármacos , Polímeros/síntese química , Polímeros/química
11.
Science ; 373(6558)2021 08 27.
Artigo em Inglês | MEDLINE | ID: mdl-34446582

RESUMO

The COVID-19 pandemic has revealed critical knowledge gaps in our understanding of and a need to update the traditional view of transmission pathways for respiratory viruses. The long-standing definitions of droplet and airborne transmission do not account for the mechanisms by which virus-laden respiratory droplets and aerosols travel through the air and lead to infection. In this Review, we discuss current evidence regarding the transmission of respiratory viruses by aerosols-how they are generated, transported, and deposited, as well as the factors affecting the relative contributions of droplet-spray deposition versus aerosol inhalation as modes of transmission. Improved understanding of aerosol transmission brought about by studies of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection requires a reevaluation of the major transmission pathways for other respiratory viruses, which will allow better-informed controls to reduce airborne transmission.


Assuntos
Microbiologia do Ar , COVID-19/transmissão , Infecções Respiratórias/transmissão , SARS-CoV-2 , Viroses/transmissão , Fenômenos Fisiológicos Virais , Aerossóis , COVID-19/virologia , Transmissão de Doença Infecciosa , Humanos , Viabilidade Microbiana , Tamanho da Partícula , Sistema Respiratório/virologia , Infecções Respiratórias/virologia , SARS-CoV-2/isolamento & purificação , SARS-CoV-2/fisiologia , Carga Viral , Viroses/virologia , Vírus/isolamento & purificação
12.
Science ; 373(6552)2021 07 16.
Artigo em Inglês | MEDLINE | ID: mdl-34437126

RESUMO

Activation of cell-autonomous defense by the immune cytokine interferon-γ (IFN-γ) is critical to the control of life-threatening infections in humans. IFN-γ induces the expression of hundreds of host proteins in all nucleated cells and tissues, yet many of these proteins remain uncharacterized. We screened 19,050 human genes by CRISPR-Cas9 mutagenesis and identified IFN-γ-induced apolipoprotein L3 (APOL3) as a potent bactericidal agent protecting multiple non-immune barrier cell types against infection. Canonical apolipoproteins typically solubilize mammalian lipids for extracellular transport; APOL3 instead targeted cytosol-invasive bacteria to dissolve their anionic membranes into human-bacterial lipoprotein nanodiscs detected by native mass spectrometry and visualized by single-particle cryo-electron microscopy. Thus, humans have harnessed the detergent-like properties of extracellular apolipoproteins to fashion an intracellular lysin, thereby endowing resident nonimmune cells with a mechanism to achieve sterilizing immunity.


Assuntos
Apolipoproteínas L/metabolismo , Membrana Celular/metabolismo , Citosol/microbiologia , Bactérias Gram-Negativas/fisiologia , Interferon gama/imunologia , Apolipoproteínas L/química , Apolipoproteínas L/genética , Membrana Externa Bacteriana/metabolismo , Bacteriólise , Sistemas CRISPR-Cas , Membrana Celular/química , Membrana Celular/ultraestrutura , Permeabilidade da Membrana Celular , Células Cultivadas , Detergentes/metabolismo , Proteínas de Ligação ao GTP/metabolismo , Edição de Genes , Bactérias Gram-Negativas/imunologia , Bactérias Gram-Negativas/patogenicidade , Bactérias Gram-Negativas/ultraestrutura , Humanos , Imunidade Inata , Lipoproteínas/química , Viabilidade Microbiana , Antígenos O/metabolismo , Domínios Proteicos , Salmonella typhimurium/imunologia , Salmonella typhimurium/patogenicidade , Salmonella typhimurium/fisiologia , Salmonella typhimurium/ultraestrutura , Solubilidade
13.
Biomed Res Int ; 2021: 9940591, 2021.
Artigo em Inglês | MEDLINE | ID: mdl-34381841

RESUMO

This study is aimed at identifying the chemical composition of the essential oil extracted from the Syzygium aromaticum seeds, as well as investigating its biological activities, insecticide effect, and allelopathic properties. The extraction yield was about 14.3 and 7.14% for grounded and ungrounded seeds, respectively. The GC-MS analysis allowed the identification of 17 heterogeneous compounds, including eugenol (68.7-87.4%), as major compound, cyperene (20.5-7.2%), phenethyl isovalerate (6.4-3.6%), and cis-thujopsene (1.9-0.8%), respectively, for grounded and ungrounded seeds. Concerning the antibacterial activity, the diameter of the inhibition zone reached 35 mm when the essential oil extracted from grounded seeds was applied against Escherichia coli. Regarding the antioxidant activity via the DPPH radical scavenging test, the IC50 varied from 1.2 ± 0.1 to 2.8 ± 0.5 µg/mL. With respect to reducing power, the efficient concentration EC50 ranged from 32 to 50 µg/mL. The essential oil exhibited also an allelopathic effect against seeds of Hyoscyamus niger, as well as an insecticide effect against Sitophilus oryzae with a DL50 value of 252.4 µL/L air. These findings enhance the use of this spice as a natural food preservative and encourage its use in several fields, including pharmaceutical, cosmetics, agriculture, and therapy, that could be a strategic way to guarantee the consumer's health.


Assuntos
Antibacterianos/química , Antioxidantes/química , Inseticidas/química , Óleos Voláteis/química , Syzygium/química , Animais , Antibacterianos/isolamento & purificação , Antibacterianos/farmacologia , Antioxidantes/isolamento & purificação , Antioxidantes/farmacologia , Testes de Sensibilidade a Antimicrobianos por Disco-Difusão , Escherichia coli/efeitos dos fármacos , Escherichia coli/crescimento & desenvolvimento , Inocuidade dos Alimentos , Cromatografia Gasosa-Espectrometria de Massas , Hyoscyamus/efeitos dos fármacos , Hyoscyamus/crescimento & desenvolvimento , Inseticidas/isolamento & purificação , Inseticidas/farmacologia , Viabilidade Microbiana/efeitos dos fármacos , Óleos Voláteis/isolamento & purificação , Óleos Voláteis/farmacologia , Óleos Vegetais/química , Óleos Vegetais/isolamento & purificação , Sementes/química , Gorgulhos/efeitos dos fármacos , Gorgulhos/crescimento & desenvolvimento
14.
Biomed Res Int ; 2021: 9930210, 2021.
Artigo em Inglês | MEDLINE | ID: mdl-34395628

RESUMO

The present study was aimed at isolating endophytic fungi from the Asian culinary and medicinal plant Lilium davidii and analyzing its antifungal and plant growth-promoting effects. In this study, the fungal endophyte Acremonium sp. Ld-03 was isolated from the bulbs of L. davidii and identified through morphological and molecular analysis. The molecular and morphological analysis confirmed the endophytic fungal strain as Acremonium sp. Ld-03. Antifungal effects of Ld-03 were observed against Fusarium oxysporum, Botrytis cinerea, Botryosphaeria dothidea, and Fusarium fujikuroi. The highest growth inhibition, i.e., 78.39 ± 4.21%, was observed for B. dothidea followed by 56.68 ± 4.38%, 43.62 ± 3.81%, and 20.12 ± 2.45% for B. cinerea, F. fujikuroi, and F. oxysporum, respectively. Analysis of the ethyl acetate fraction through UHPLC-LTQ-IT-MS/MS revealed putative secondary metabolites which included xanthurenic acid, valyl aspartic acid, gancidin W, peptides, and cyclic dipeptides such as valylarginine, cyclo-[L-(4-hydroxy-Pro)-L-leu], cyclo(Pro-Phe), and (3S,6S)-3-benzyl-6-(4-hydroxybenzyl)piperazine-2,5-dione. Other metabolites included (S)-3-(4-hydroxyphenyl)-2-((S)-pyrrolidine-2-carboxamido)propanoic acid, dibutyl phthalate (DBP), 9-octadecenamide, D-erythro-C18-Sphingosine, N-palmitoyl sphinganine, and hydroxypalmitoyl sphinganine. The strain Ld-03 showed indole acetic acid (IAA) production with or without the application of exogenous tryptophan. The IAA ranged from 53.12 ± 3.20 µg ml-1 to 167.71 ± 7.12 µg ml-1 under different tryptophan concentrations. The strain was able to produce siderophore, and its production was significantly decreased with increasing Fe(III) citrate concentrations in the medium. The endophytic fungal strain also showed production of organic acids and phosphate solubilization activity. Plant growth-promoting effects of the strain were evaluated on in vitro seedling growth of Allium tuberosum. Application of 40% culture dilution resulted in a significant increase in root and shoot length, i.e., 24.03 ± 2.71 mm and 37.27 ± 1.86 mm, respectively, compared to nontreated control plants. The fungal endophyte Ld-03 demonstrated the potential of conferring disease resistance and plant growth promotion. Therefore, we conclude that the isolated Acremonium sp. Ld-03 should be further investigated before utilization as a biocontrol agent and plant growth stimulator.


Assuntos
Acremonium/química , Antifúngicos/farmacologia , Ascomicetos/crescimento & desenvolvimento , Botrytis/crescimento & desenvolvimento , Fusarium/crescimento & desenvolvimento , Lilium/microbiologia , Reguladores de Crescimento de Plantas/farmacologia , Acetatos/química , Acetatos/farmacologia , Acremonium/isolamento & purificação , Acremonium/fisiologia , Antifúngicos/química , Ascomicetos/efeitos dos fármacos , Botrytis/efeitos dos fármacos , Cebolinha-Francesa/efeitos dos fármacos , Cebolinha-Francesa/crescimento & desenvolvimento , Cromatografia Líquida de Alta Pressão , Resistência à Doença , Endófitos/isolamento & purificação , Endófitos/fisiologia , Fusarium/efeitos dos fármacos , Ácidos Indolacéticos/química , Ácidos Indolacéticos/isolamento & purificação , Ácidos Indolacéticos/farmacologia , Metabolômica/métodos , Testes de Sensibilidade Microbiana , Viabilidade Microbiana/efeitos dos fármacos , Desenvolvimento Vegetal , Reguladores de Crescimento de Plantas/química , Reguladores de Crescimento de Plantas/isolamento & purificação , Raízes de Plantas/microbiologia , Metabolismo Secundário , Espectrometria de Massas em Tandem
15.
Int J Food Microbiol ; 356: 109364, 2021 Oct 16.
Artigo em Inglês | MEDLINE | ID: mdl-34418698

RESUMO

Inactivation rate constant or inactivation coefficient (specific lethality) quantifies the rate at which a chemical sanitizer inactivates a microorganism. This study presents a modified disinfection kinetics model to evaluate the potential effect of organic content on the chlorine inactivation coefficient of Escherichia coli O157:H7 in fresh produce wash processes. Results show a significant decrease in the bactericidal efficacy of free chlorine (FC) in the presence of organic load compared to its absence. While the chlorine inactivation coefficient of Escherichia coli O157:H7 is 70.39 ± 3.19 L/mg/min in the absence of organic content, it drops by 73% for a chemical oxygen demand (COD) level of 600-800 mg/L. Results also indicate that the initial chlorine concentration and bacterial load have no effect on the chlorine inactivation coefficient. A second-order chemical reaction model for FC decay, which utilizes a proportion of COD as an indicator of organic content in fresh produce wash was employed, yielding an apparent reaction rate of (9.45 ± 0.22) × 10-4 /µM/min. This model was validated by predicting FC concentration in multi-run continuous wash cycles with periodic replenishment of chlorine.


Assuntos
Cloro , Escherichia coli O157 , Manipulação de Alimentos , Microbiologia de Alimentos , Viabilidade Microbiana , Modelos Biológicos , Cloro/farmacologia , Contagem de Colônia Microbiana , Desinfetantes/farmacologia , Escherichia coli O157/efeitos dos fármacos , Manipulação de Alimentos/métodos , Microbiologia de Alimentos/métodos
16.
Biomed Res Int ; 2021: 1057531, 2021.
Artigo em Inglês | MEDLINE | ID: mdl-34435040

RESUMO

Nowadays, production of functional foods has become very essential. Inulin is one of the most functional hydrocolloid compounds used in such products. In the present study, the production of a synbiotic yogurt containing 1, 2.5, and 5% (w/v) inulin has been investigated. The yogurt was fermented with Lactobacillus brevis PML1 derived from Tarkhineh, an Iranian cereal-dairy fermented food. Furthermore, the physicochemical properties, antioxidant activity, sensory attributes, and microbial viability properties were investigated on the 0th, 7th, and 14th days of storage after fermentation. The viable cells of L. brevis PML1 reached 108 CFU/g, and the product resisted to simulated digestive juices. Moreover, the synbiotic yogurt impressively increased the production of antimicrobial compounds and had the most profound antimicrobial effect on S. typhimurium. The physiochemical properties were in the normal range, and the fat content of the synbiotic yogurt was reduced remarkably. The antioxidant capacity of the fermented yogurt was significantly increased (p < 0.05), which was equal to those of DPPH (69.18 ± 1.00%) and BHA (89.16 ± 2.00%). The viability of L. brevis PML1 was increased during storage. Sensory analysis showed that there were significant differences in terms of the impressive parameters between the samples and the control (p < 0.05). Addition of 2.5% inulin not only improved the physical properties but also retained the viability of the probiotic after 14 days of storage, in addition to the viability of L. brevis with a viability count above 6 log CFU/g in the yogurt. Therefore, a novel synbiotic product containing L. brevis PML1, which can exert the desired properties, can be used as a suitable carrier for the delivery of the probiotic strain, exerting its beneficial health effects.


Assuntos
Laticínios/microbiologia , Grão Comestível/microbiologia , Lactobacillus brevis/metabolismo , Simbióticos/análise , Iogurte/microbiologia , Antioxidantes/análise , Fermentação , Inulina/análise , Irã (Geográfico) , Lactobacillus brevis/crescimento & desenvolvimento , Lactobacillus brevis/isolamento & purificação , Viabilidade Microbiana , Iogurte/análise
17.
Colloids Surf B Biointerfaces ; 206: 111950, 2021 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-34218012

RESUMO

Escherichia coli is one of the most common commensal aerobic bacteria in the gut microbiota of humans (and other mammals). Nevertheless, if left free to proliferate, it can induce a large range of diseases from diarrhoea to extra-intestinal diseases. In recent years, this bacterium had become increasingly resistant to antibiotics. It is therefore essential to implement new approaches able to maintain both bacterial viability and to control their proliferation. In this context, we developed a process to encapsulate Escherichia coli in polymer shells. We took advantage of the fact that this bacterium has a negatively charged surface and modified it via a layer-by-layer process, i.e. with oppositely charged polyelectrolyte pairs (namely chitosan as the polycation and alginate or dextran sulfate as polyanion). We successfully demonstrate the controlled coating of the bacterial surface via zeta potential measurement, the viability of the encapsulated bacteria and a delay in growth due to the multilayer coating. This delay was dependent on the number of polyelectrolyte layers.


Assuntos
Quitosana , Escherichia coli , Alginatos , Animais , Antibacterianos/farmacologia , Humanos , Viabilidade Microbiana
18.
Nat Commun ; 12(1): 4649, 2021 07 30.
Artigo em Inglês | MEDLINE | ID: mdl-34330925

RESUMO

The bacterium Vibrio cholerae can colonize the human intestine and cause cholera, but spends much of its life cycle in seawater. The pathogen must adapt to substantial environmental changes when moving between seawater and the human intestine, including different availability of carbon sources such as fructose. Here, we use in vitro experiments as well as mouse intestinal colonization assays to study the mechanisms used by pandemic V. cholerae to adapt to these environmental changes. We show that a LacI-type regulator (FruI) and a fructose/H+ symporter (FruT) are important for fructose uptake at low fructose concentrations, as those found in seawater. FruT is downregulated by FruI, which is upregulated when O2 concentrations are low (as in the intestine) by ArcAB, a two-component system known to respond to changes in oxygen levels. As a result, the bacteria predominantly use FruT for fructose uptake under seawater conditions (low fructose, high O2), and use a known fructose phosphotransferase system (PTS, Fpr) for fructose uptake under conditions found in the intestine. PTS activity leads to reduced levels of intracellular cAMP, which in turn upregulate virulence genes. Our results indicate that the FruT/FruI system may be important for survival of pandemic V. cholerae in seawater.


Assuntos
Proteínas de Bactérias/metabolismo , Frutose/metabolismo , Simportadores/metabolismo , Vibrio cholerae/metabolismo , Animais , Proteínas de Bactérias/genética , Cólera/epidemiologia , Cólera/microbiologia , Feminino , Regulação Bacteriana da Expressão Gênica , Genoma Bacteriano/genética , Genômica/métodos , Humanos , Masculino , Camundongos , Viabilidade Microbiana/genética , Pandemias , Regiões Promotoras Genéticas/genética , Ligação Proteica , Água do Mar/microbiologia , Simportadores/genética , Vibrio cholerae/genética , Vibrio cholerae/patogenicidade , Virulência/genética
19.
Water Res ; 201: 117355, 2021 Aug 01.
Artigo em Inglês | MEDLINE | ID: mdl-34256318

RESUMO

While the impact of suspended solids on chemical disinfection kinetics has been widely recognized, a detailed modeling framework for assessing their contribution on disinfection efficiency in municipal contact tanks is yet unavailable. In this paper, we conducted experimental and modeling studies to mechanistically describe the interplay between suspended solids (not removed by gravity settling in secondary clarifiers) and disinfection performance of an emerging disinfectant, peracetic acid, operated in a municipal contact tank. Specifically, we developed an integrated computational fluid dynamics (CFD) model to simultaneously predict the fate and transport of suspended solids, Escherichia coli and peracetic acid in a hypothetical reactor using an exposure-based (i.e., CT-based) inactivation rate expression. The integrated CFD model, calibrated against laboratory data, was used to gain insights on the vertical distribution and local PAA decay effect associated with solids settling and their impact on disinfectant decay and microbial inactivation. Results indicated that: (a) solids settling in contact tanks is a significant phenomenon that cannot be neglected, which can substantially impact disinfection efficiency under low flow conditions; (b) vertical solids distribution and stratification in contact tanks can strongly affect Escherichia coli inactivation by peracetic acid, as highlighted by the CFD modeling studies; (c) Escherichia coli settling is experimentally measurable, and strongly correlated with solids settling. These phenomena can be successfully integrated into a CFD model to obtain a comprehensive description of the PAA disinfection process in presence of changes in secondary effluent quality and flow, a situation typically encountered in municipal contact tanks operated in full scale wastewater treatment plants.


Assuntos
Desinfetantes , Purificação da Água , Desinfecção , Hidrodinâmica , Cinética , Viabilidade Microbiana , Ácido Peracético , Eliminação de Resíduos Líquidos , Águas Residuárias
20.
Ultrason Sonochem ; 76: 105660, 2021 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-34271395

RESUMO

A novel technique for treating grass carp by combining plasma functionalized liquids and ultrasound to inactivate bacteria was developed. The effects of the plasma functionalized liquids (PFL) including plasma functionalized water (PFW) and buffer (PFB) and their respective combination with ultrasound treatment (USPFW and USPFB) on the oxidative and physical qualities of grass carp were also investigated. Individual applications of PFW and PFB significantly reduced the populations of Escherichia coli and Shewanella putrefaciens in the range of 0.31-1.18 log CFU/g, compared with the control with a reduction of 0.18 log CFU/g, while combined treatments of USPFW and USPFB presented additional reductions of 0.05-0.65 log CFU/g, with potential synergy demonstrated for PFW and ultrasound. The treatment resulted in improved biomedical index and nutritional value of fatty acids and lipids, protein structural unfolding, increased lipid oxidation and protein degradation with values within the acceptable limits, and the combined treatment was more effective for retarding the hardness reduction in grass carp, while the colour change was also significantly affected, resulting in increased whiteness. The results indicated that the combined treatments may be a promising approach to improving the quality of seafood products.


Assuntos
Carpas/microbiologia , Qualidade dos Alimentos , Viabilidade Microbiana/efeitos dos fármacos , Gases em Plasma/farmacologia , Ondas Ultrassônicas , Animais
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