Your browser doesn't support javascript.
Mostrar: 20 | 50 | 100
Resultados 1 - 20 de 1.453
Filtrar
1.
Int J Food Microbiol ; 313: 108381, 2020 Jan 16.
Artigo em Inglês | MEDLINE | ID: mdl-31670167

RESUMO

As a raw agricultural commodity, wheat is exposed to microbial contamination; therefore, enteric pathogens may be among its microbiota creating a food safety risk in milled products. This research evaluates (1) the effectiveness of organic acids dissolved in saline solutions to reduce the counts of pathogenic microorganisms in soft and hard wheat, and also investigates the effect of seasonal temperature on (2) survivability of pathogens in wheat kernels and on (3) pathogen inactivation during tempering with saline organic acid solutions. Wheat samples were inoculated with cocktails of either 5 serovars of Salmonella enterica, 5 E. coli O157:H7 or 6 non-O157 Shiga toxin-producing E. coli (STEC) strains to achieve a concentration of ~7 log CFU/g. Inoculated samples were allowed to stand for 7-days at temperatures (2.0, 10.8, 24.2, 32 °C) corresponding to those experienced during winter, spring/fall, and summer (average and maximum) in the main wheat growing regions in the state of Nebraska, USA. Besides water, solutions containing acid (acetic or lactic 2.5% or 5.0% v/v) and NaCl (~26% w/v) were used for tempering the wheat to 15.0% (soft) and 15.5% (hard) moisture at the different seasonal temperatures. The survival of pathogenic microorganisms throughout the resting period, and before and after tempering was analyzed by plating samples on injury-recovery media. The survival rate of pathogenic microorganisms on wheat kernels was higher at temperatures experienced during the winter (2.0 °C) and spring/fall (10.8 °C) months. Regardless of tempering temperature, the initial pathogen load was reduced significantly by all solutions when compared to the control tempered with water (P ≤ .05). The combination of lactic acid (5.0%) and NaCl was the most effective treatment against Salmonella enterica, E. coli O157:H7 and non-O157 STEC, with average reduction values of 1.8, 1.8 and 1.6 log CFU/g for soft wheat and 2.6, 2.4 and 2.4 log CFU/g for hard wheat, respectively. Implementation of organic acids and NaCl in tempering water may have the potential to reduce the risk of pathogen contamination in milled products.


Assuntos
Ácidos/farmacologia , Manipulação de Alimentos/métodos , Cloreto de Sódio/farmacologia , Triticum/microbiologia , Ácidos/química , Contagem de Colônia Microbiana , Escherichia coli O157/efeitos dos fármacos , Escherichia coli O157/crescimento & desenvolvimento , Manipulação de Alimentos/instrumentação , Microbiologia de Alimentos , Inocuidade dos Alimentos , Salmonella enterica/efeitos dos fármacos , Salmonella enterica/crescimento & desenvolvimento , Estações do Ano , Temperatura Ambiente
2.
Food Microbiol ; 86: 103312, 2020 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-31703872

RESUMO

Some Listeria monocytogenes strains are persistent in food processing environments, where this pathogen may be subjected to various stresses. This study aimed to elucidate the response of persistent strains of L. monocytogenes to low pH and H2O2 exposure. Almost all of the persistent strains examined were highly susceptible to low pH, whereas H2O2 susceptibility was comparable to that of control strains. Two persistent strains isolated from the same sample, however, exhibited lower susceptibility to low pH. These findings suggest an acid-susceptible phenotype predominates in the habitat, indicating that environmental conditions contribute to the establishment of persistence. Representative strains exhibiting acid-susceptible and less acid-susceptible phenotypes were further investigated regarding acid response characteristics. Less acid-susceptible strains exhibited increased survival in acidified brain heart infusion (BHI) broth compared with acidified phosphate-buffered saline (PBS). These strains also exhibited increased survival in acidified PBS containing glucose and glutamate, which are involved in acid response mechanisms, compared with acidified PBS alone. However, neither acidified BHI broth nor exogenous glucose and glutamate increased survival of acid-susceptible strains. An adaptive acid tolerance response of the acid-susceptible phenotype was observed, but this was limited compared with that of the less acid-susceptible phenotype.


Assuntos
Ácidos/farmacologia , Listeria monocytogenes/efeitos dos fármacos , Contagem de Colônia Microbiana , Meios de Cultura/química , Meios de Cultura/metabolismo , Microbiologia de Alimentos , Peróxido de Hidrogênio/farmacologia , Concentração de Íons de Hidrogênio , Listeria monocytogenes/crescimento & desenvolvimento , Listeria monocytogenes/metabolismo
3.
J Ind Microbiol Biotechnol ; 46(11): 1491-1503, 2019 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-31512094

RESUMO

Komagataeibacter hansenii HDM1-3 (K. hansenii HDM1-3) has been widely applied for producing bacterial cellulose (BC). The yield of BC has been frequently limited by the acidification during sugar metabolism, due to the generation of organic acids such as acetic acid. In this study, the acid resistance mechanism of K. hansenii HDM1-3 has been investigated from the aspect of metabolic adaptability of cell membrane fatty acids. Firstly, we observed that the survival rate of K. hansenii HDM1-3 was decreased with lowered pH values (adjusted with acetic acids), accompanied by increased leakage rate. Secondly, the cell membrane adaptability in response to acid stress was evaluated, including the variations of cell membrane fluidity and fatty acid composition. The proportion of unsaturated fatty acids was increased (especially, C18-1w9c and C19-Cyc), unsaturation degree and chain length of fatty acids were also increased. Thirdly, the potential molecular regulation mechanism was further elucidated. Under acid stress, the fatty acid synthesis pathway was involved in the structure and composition variations of fatty acids, which was proved by the activation of both fatty acid dehydrogenase (des) and cyclopropane fatty acid synthase (cfa) genes, as well as the addition of exogenous fatty acids. The fatty acid synthesis of K. hansenii HDM1-3 may be mediated by the activation of two-component sensor signaling pathways in response to the acid stress. The acid resistance mechanism of K. hansenii HDM1-3 adds to our knowledge of the acid stress adaptation, which may facilitate the development of new strategies for improving the industrial performance of this species under acid stress.


Assuntos
Acetobacteraceae/metabolismo , Ácidos Graxos/metabolismo , Acetobacteraceae/efeitos dos fármacos , Acetobacteraceae/genética , Ácidos/farmacologia , Adaptação Fisiológica , Membrana Celular/metabolismo , Fluidez de Membrana , Metiltransferases/metabolismo , Oxirredutases/metabolismo
4.
J Ind Microbiol Biotechnol ; 46(11): 1621-1629, 2019 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-31414323

RESUMO

During fermentation, acid stress caused by the accumulation of acidic metabolites seriously affects the metabolic activity and production capacity of microbial cells. To elucidate the acid stress-tolerance mechanisms of microbial cells, we performed genome mutagenesis combined with high-throughput technologies to screen acid stress-tolerant strains. Mutant strain Lactococcus lactis WH101 showed a 16,000-fold higher survival rate than that of the parent strain after 5 h of acid shock at pH 4.0 and maintained higher ATP, NH4+, and intracellular pH (pHi) levels during acid stress. Additionally, comparative transcriptomics analysis revealed enhanced regulation of carbohydrate metabolism and sugar transport to provide additional energy, amino acid metabolism and transport to maintain pHi homeostasis and ATP generation, and fatty acid metabolism to enhance cellular acid tolerance. Moreover, overexpression of identified components resulted in 12.6- and 12.9-fold higher survival rates after acid shock for 3 h at pH 4.0 in L. lactis (ArcB) and L. lactis (MalQ) compared to the control strain, respectively. These findings provide valuable insight into the acid stress-response mechanisms of L. lactis and promote the further development of robust industrial strains.


Assuntos
Lactococcus lactis/metabolismo , Ácidos/farmacologia , Fermentação , Homeostase , Concentração de Íons de Hidrogênio , Lactococcus lactis/efeitos dos fármacos , Lactococcus lactis/genética , Estresse Fisiológico , Transcriptoma
5.
Genes (Basel) ; 10(8)2019 08 10.
Artigo em Inglês | MEDLINE | ID: mdl-31405132

RESUMO

We reported changes in the co-regulated mRNA expression in iron walnut (Juglans sigillata) in response to soil pH treatments and identified mRNAs specific to acidic soil conditions. Phenotypic and physiological analyses revealed that iron walnut growth was greater for the pH 4-5 and pH 5-6 treatments than for the pH 3-4 and pH 6-7 treatments. A total of 2768 differentially expressed genes were detected and categorized into 12 clusters by Short Time-series Expression Miner (STEM). The 994 low-expression genes in cluster III and 255 high-expression genes in cluster X were classified as acid-responsive genes on the basis of the relationships between phenotype, physiology, and STEM clustering, and the two gene clusters were analyzed by a maximum likelihood (ML) evolutionary tree with the greatest log likelihood values. No prominent sub-clusters occurred in cluster III, but three occurred in cluster X. The Kyoto Encyclopedia of Genes and Genomes (KEGG) analysis indicated that acid-responsive genes were related primarily to arginine biosynthesis and the arginine/proline metabolism pathway, implying that polyamine accumulation may enhance iron walnut acid stress tolerance. Overall, our results revealed 1249 potentially acid-responsive genes in iron walnut, indicating that its response to acid stress involves different pathways and activated genes.


Assuntos
Genes de Plantas , Juglans/genética , Poliaminas/metabolismo , Estresse Fisiológico , Transcriptoma , Ácidos/análise , Ácidos/farmacologia , Regulação da Expressão Gênica de Plantas , Juglans/efeitos dos fármacos , Juglans/metabolismo , Solo/química
6.
Artigo em Chinês | MEDLINE | ID: mdl-31327193

RESUMO

Objective:The purpose of the present study was to explore the characteristics and differentiation of somatic cells in vitro undergoing a low pH treatment, so as to provide new therapeutic strategies for treating sensorineural hearing loss.Method: The human mature somatic cells were selected as the target cells, and the cells were treated with different pH values to observe the cell morphology. The cell characteristics were identified from alkaline phosphatase (AKP) activity, immunohistochemical staining and molecular biology, and the most suitable pH value was selected. In addition, a mouse model of the cochlear lesion was constructed using bilirubin. Subsequently, the characteristics and therapeutic effect of somatic cells undergoing low pH treatment were examined by morphology, AKP activity, immunofluorescence assay and Q-PCR.Result:The cell growth of the experimental group was significantly better than those in the control group. The activity of AKP in the experimental group was higher than that in the control group. The expression of Nanog and Oct4 was both positive in the two groups. When the cells were changed to neurobasol medium, the marker of Nestin was positive.Conclusion:The human somatic cells undergoing a low pH treatment showed the similar characteristics as those of induced pluripotent stem (iPS) cells; although the functions and therapeutic effect of these altered human somatic cells need to be further studied.


Assuntos
Ácidos/farmacologia , Diferenciação Celular , Células Cultivadas/citologia , Células Cultivadas/efeitos dos fármacos , Animais , Humanos , Concentração de Íons de Hidrogênio , Células-Tronco Pluripotentes Induzidas/citologia , Células-Tronco Pluripotentes Induzidas/efeitos dos fármacos , Camundongos
7.
Int J Mol Sci ; 20(14)2019 Jul 16.
Artigo em Inglês | MEDLINE | ID: mdl-31315225

RESUMO

Cariogenic oral biofilms are strongly linked to dental caries around dental sealants. Quaternary ammonium monomers copolymerized with dental resin systems have been increasingly explored for modulation of biofilm growth. Here, we investigated the effect of dimethylaminohexadecyl methacrylate (DMAHDM) on the cariogenic pathogenicity of Streptococcus mutans (S. mutans) biofilms. DMAHDM at 5 mass% was incorporated into a parental formulation containing 20 mass% nanoparticles of amorphous calcium phosphate (NACP). S. mutans biofilms were grown on the formulations, and biofilm inhibition and virulence properties were assessed. The tolerances to acid stress and hydrogen peroxide stress were also evaluated. Our findings suggest that incorporating 5% DMAHDM into 20% NACP-containing sealants (1) imparts a detrimental biological effect on S. mutans by reducing colony-forming unit counts, metabolic activity and exopolysaccharide synthesis; and (2) reduces overall acid production and tolerance to oxygen stress, two major virulence factors of this microorganism. These results provide a perspective on the value of integrating bioactive restorative materials with traditional caries management approaches in clinical practice. Contact-killing strategies via dental materials aiming to prevent or at least reduce high numbers of cariogenic bacteria may be a promising approach to decrease caries in patients at high risk.


Assuntos
Antibacterianos/farmacologia , Biofilmes , Cimentos Dentários/química , Metacrilatos/farmacologia , Streptococcus mutans/efeitos dos fármacos , Ácidos/farmacologia , Antibacterianos/química , Fosfatos de Cálcio/química , Fosfatos de Cálcio/farmacologia , Peróxido de Hidrogênio/farmacologia , Metacrilatos/química , Streptococcus mutans/patogenicidade , Streptococcus mutans/fisiologia
8.
Food Microbiol ; 83: 150-158, 2019 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-31202406

RESUMO

The occurrence of thermophilic spore formers in dairy powders is a major concern for producers worldwide. This study aims to investigate the resistance of thermophilic endospores towards cleaning solutions typically used for cleaning-in-place in dairy manufacturing plants. From eleven tested strains, all were able to survive an alkaline treatment (NaOH) at 65 °C for 10 min (0.5%), whereas at concentrations of 2% eight strains withstood the treatment. Acid solutions were more sporicidal. At 0.5% of HNO3, only three strains survived the treatment. Milk impurities reduced the inactivation effect of the NaOH solutions towards thermophilic spore formers. For two selected strains, a detailed kinetic inactivation in NaOH and HNO3 solutions at different temperatures was performed and non-log-linear inactivation curves were observed. This study highlights the risk of reusing cleaning solutions in dairies.


Assuntos
Ácidos/farmacologia , Álcalis/farmacologia , Viabilidade Microbiana/efeitos dos fármacos , Leite/microbiologia , Esporos Bacterianos/efeitos dos fármacos , Temperatura Ambiente , Animais , Contagem de Colônia Microbiana , Indústria de Laticínios , Farmacorresistência Bacteriana , Concentração de Íons de Hidrogênio , Cinética , Pós , Proteínas do Soro do Leite/metabolismo
9.
Molecules ; 24(9)2019 May 02.
Artigo em Inglês | MEDLINE | ID: mdl-31052602

RESUMO

In this study, effects of different pretreatment methods on the enzymatic digestibility of Pennisetum alopecuroides, a ubiquitous wild grass in China, were investigated to evaluate its potential as a feedstock for biofuel production. The stalk samples were separately pretreated with H2SO4, NaOH and FeCl3 solutions of different concentrations at 120 °C for 30 min, after which enzymatic hydrolysis was conducted to measure the digestibility of pretreated samples. Results demonstrated that different pretreatments were effective at removing hemicellulose, among which ferric chloride pretreatment (FCP) gave the highest soluble sugar recovery (200.2 mg/g raw stalk) from the pretreatment stage. In comparison with FCP and dilute acid pretreatment (DAP), dilute alkaline pretreatment (DALP) induced much higher delignification and stronger morphological changes of the biomass, making it more accessible to hydrolysis enzymes. As a result, DALP using 1.2% NaOH showed the highest total soluble sugar yield through the whole process from pretreatment to enzymatic hydrolysis (508.5 mg/g raw stalk). The present work indicates that DALP and FCP have the potential to enhance the effective bioconversion of lignocellulosic biomass like P. alopecuroides, hence making this material a valuable and promising energy plant.


Assuntos
Ácidos/farmacologia , Antiácidos/farmacologia , Cloretos/farmacologia , Enzimas/metabolismo , Compostos Férricos/farmacologia , Pennisetum/efeitos dos fármacos , Pennisetum/metabolismo , Biomassa , Fermentação , Hidrólise/efeitos dos fármacos , Açúcares/metabolismo
10.
Int J Food Microbiol ; 301: 27-33, 2019 Jul 16.
Artigo em Inglês | MEDLINE | ID: mdl-31082697

RESUMO

Pre-chilling leads to a temperature decline of the pre-rigor muscle of poultry carcasses, and a reduction of the initial bacterial load may occur. Both ultrasound (US) and slightly acidic electrolyzed water (SAEW) have been used alone in the meat industry for the manufacture of emulsions, pasteurization, and prevention of bacteria growth. However, the impact of the combination of these technologies during the pre-chilling of chicken carcasses has not been evaluated. In this study, breast chicken cylinders (CBCs) were pre-chilled for 10 min at 10 °C using SAEW and different US frequencies (25 and 130 kHz). The microbiological characteristics, lipid and protein oxidation, shear force, and anaerobic glycolysis were evaluated. The US + SAEW combination led to an effective reduction (P < 0.05) of enterobacteria, mesophilic bacteria, lactic acid bacteria, and psychrotrophic bacteria, while the lipid and protein oxidation, shear force, anaerobic glycolysis, and muscle structure were not affected (P > 0.05). Therefore, the combination of these technologies may be promising in the pre-chilling stage of chicken carcasses.


Assuntos
Ácidos/farmacologia , Carga Bacteriana/efeitos dos fármacos , Microbiologia de Alimentos/métodos , Carne/microbiologia , Ultrassom/normas , Animais , Galinhas/microbiologia , Temperatura Baixa , Eletrólise , Água/química
11.
Aquat Toxicol ; 212: 120-127, 2019 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-31103733

RESUMO

Ocean acidification (OA) has the potential to alter the bioavailability of pH sensitive metals contaminating coastal sediments, particularly copper, by changing their speciation in seawater. Hence OA may drive increased toxicity of these metals to coastal biota. Here, we demonstrate complex interactions between OA and copper on the physiology and toxicity responses of the sediment dwelling polychaete Alitta virens. Worm coelomic fluid pCO2 was not increased by exposure to OA conditions (pHNBS 7.77, pCO2 530 µatm) for 14 days, suggesting either physiological or behavioural responses to control coelomic fluid pCO2. Exposure to 0.25 µM nominal copper caused a decrease in coelomic fluid pCO2 by 43.3% and bicarbonate ions by 44.6% but paradoxically this copper-induced effect was reduced under near-future OA conditions. Hence OA appeared to 'buffer' the copper-induced acid-base disturbance. DNA damage was significantly increased in worms exposed to copper under ambient pCO2 conditions, rising by 11.1% compared to the worms in the no copper control, but there was no effect of OA conditions on the level of DNA damage induced by copper when exposed in combination. These interactions differ from the increased copper toxicity under OA conditions reported for several other invertebrate species. Hence this new evidence adds to the developing paradigm that species' physiology is key in determining the interactions of these two stressors rather than it purely being driven by the changes in metal chemistry under lower seawater pH.


Assuntos
Cobre/toxicidade , Poliquetos/efeitos dos fármacos , Água do Mar/química , Ácidos/farmacologia , Animais , Tampões (Química) , Dano ao DNA/efeitos dos fármacos , Poluentes Químicos da Água/toxicidade
12.
Int J Food Microbiol ; 299: 47-57, 2019 Jun 16.
Artigo em Inglês | MEDLINE | ID: mdl-30953995

RESUMO

The aim of this work was to study the influence of lemon and vinegar marinades on Salmonella inoculated on chicken fillets and stored under different storage temperatures for nine days in the presence of indigenous microbiota. In addition to this, model development for the determination of the inactivation boundaries and the prediction of pathogens response was attempted. The different acid concentrations in the marinades, the type of acid, the storage temperature as well as the duration of storage impacted the levels of pathogens and background flora. The higher tested concentrations (2% and 4% v/v for acetic and citric acid) were more effective against Salmonella and spoilage microorganisms than the lower ones (0.5 and 1% v/v for acetic and citric acid), while the intermediate concentrations (1, 1.5 and 2, 3% v/v for acetic and citric acid, respectively) presented differentiations of particular interest to the microbial responses to acidic stress. The aforementioned parameters also differentiated Salmonella serovars persistence and spoilage microorganisms dominance. Regarding model development, the probability of inactivation of Salmonella was satisfactorily predicted particularly in the case of acetic acid marination while in model validation, the majority of the vinegar marinated samples were correctly classified, whereas, in case of lemon marination, a higher number of misclassifications was observed, indicating a partial weakness of the model to predict the pathogens response at interface concentrations.


Assuntos
Microbiologia de Alimentos , Carne/microbiologia , Viabilidade Microbiana , Salmonella/fisiologia , Temperatura Ambiente , Ácidos/farmacologia , Animais , Galinhas , Contagem de Colônia Microbiana , Viabilidade Microbiana/efeitos dos fármacos , Salmonella/efeitos dos fármacos , Salmonella/crescimento & desenvolvimento , Fatores de Tempo
13.
Prog Mol Subcell Biol ; 58: 85-109, 2019.
Artigo em Inglês | MEDLINE | ID: mdl-30911890

RESUMO

Zygosaccharomyces bailii and two closely related species, Z. parabailii and Z. pseudobailii ("Z. bailii species complex", "Z. bailii sensu lato" or simply "Z. bailii (s.l.)"), are frequently implicated in the spoilage of acidified preserved foods and beverages due to their tolerance to very high concentrations of weak acids used as food preservatives. The recent sequencing and annotation of these species' genomes have clarified their genomic organization and phylogenetic relationship, which includes events of interspecies hybridization. Mechanistic insights into their adaptation and tolerance to weak acids (e.g., acetic and lactic acids) are also being revealed. Moreover, the potential of Z. bailii (s.l.) to be used in industrial biotechnological processes as interesting cell factories for the production of organic acids, reduction of the ethanol content, increase of alcoholic beverages aroma complexity, as well as of genetic source for increasing weak acid resistance in yeast, is currently being considered. This chapter includes taxonomical, ecological, physiological, and biochemical aspects of Z. bailii (s.l.). The focus is on the exploitation of physiological genomics approaches that are providing the indispensable holistic knowledge to guide the effective design of strategies to overcome food spoilage or the rational exploitation of these yeasts as promising cell factories.


Assuntos
Ácidos/metabolismo , Genômica , Zygosaccharomyces/genética , Zygosaccharomyces/metabolismo , Ácidos/farmacologia , Filogenia , Zygosaccharomyces/classificação , Zygosaccharomyces/efeitos dos fármacos
14.
Int J Mol Sci ; 20(5)2019 Mar 04.
Artigo em Inglês | MEDLINE | ID: mdl-30836626

RESUMO

A deeper understanding of the detailed mechanism of in vivo tissue healing is necessary for the development of novel regenerative therapies. Among several external factors, environmental pH is one of the crucial parameters that greatly affects enzyme activity and cellular biochemical reactions involving tissue repair and homeostasis. In this study, in order to analyze the microenvironmental conditions during bone healing, we first measured the pH in vivo at the bone healing site using a high-resolution fiber optic pH microsensor directly in femur defects and tooth extraction sockets. The pH was shown to decrease from physiological 7.4 to 6.8 during the initial two days of healing (inflammatory phase). In the same initial stages of the inflammatory phase of the bone healing process, mesenchymal stem cells (MSCs) are known to migrate to the healing site to contribute to tissue repair. Therefore, we investigated the effect of a short-term acidic (pH 6.8) pre-treatment on the stemness of bone marrow-derived MSCs (BMSCs). Interestingly, the results showed that pre-treatment of BMSCs with acidic pH enhances the expression of stem cell markers (OCT-4, NANOG, SSEA-4), as well as cell viability and proliferation. On the other hand, acidic pH decreased BMSC migration ability. These results indicate that acidic pH during the initial stages of bone healing is important to enhance the stem cell properties of BMSCs. These findings may enable the development of novel methods for optimization of stem cell function towards tissue engineering or regenerative medicine.


Assuntos
Ácidos/farmacologia , Regeneração Óssea/genética , Osteogênese/efeitos dos fármacos , Engenharia Tecidual/métodos , Animais , Células da Medula Óssea/citologia , Células da Medula Óssea/efeitos dos fármacos , Regeneração Óssea/efeitos dos fármacos , Diferenciação Celular/efeitos dos fármacos , Proliferação de Células/efeitos dos fármacos , Sobrevivência Celular/efeitos dos fármacos , Microambiente Celular/efeitos dos fármacos , Humanos , Concentração de Íons de Hidrogênio/efeitos dos fármacos , Transplante de Células-Tronco Mesenquimais , Células-Tronco Mesenquimais/citologia , Células-Tronco Mesenquimais/efeitos dos fármacos , Camundongos , Proteína Homeobox Nanog/genética , Fator 3 de Transcrição de Octâmero/genética , Medicina Regenerativa , Antígenos Embrionários Estágio-Específicos/genética , Células-Tronco/citologia , Células-Tronco/efeitos dos fármacos , Cicatrização/genética
15.
J Food Sci ; 84(3): 599-605, 2019 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-30730584

RESUMO

Acid adaptation in Salmonella Enteritidis was characterized by phenotypic and gene-expression analyses. S. Enteritidis cells at log-phase and stationary-phase were kept at pH 4.5 to 6.0 for 1 to 4 hours. All treatments induced various levels of acid tolerance response that were dependent on pH, exposure time and growth phase. This acid adaptation resulted in tolerance to 50 °C and 8% NaCl regardless of the growth phase. However, the tolerance of log-phase and stationary-phase cells to low temperatures (4 and -20 °C) was increased and decreased, respectively. RT-qPCR analysis revealed that genes involved in tolerance to acid (SEN1564A and cfa), heat (rpoH, uspB, and htrA), salt (proP, proV, and osmW), and cold (cspA, cspC, and csdA) stress were generally upregulated after acid adaptation. These results provide an initial insight into mechanisms of acid adaptation and induced cross protection in S. Enteritidis. PRACTICAL APPLICATION: Stress tolerance acquisition resulting from acid adaptation in foodborne pathogens poses a great threat to food safety. The current work showed that acid adaptation induced direct tolerance and cross-tolerance to high temperature, low temperature, and salt in Salmonella Enteritidis, possibly due to the upregulation of stress tolerance-related genes. These results provide key insights into acid adaptation mechanisms and efficient control of S. Enteritidis.


Assuntos
Ácidos/farmacologia , Adaptação Fisiológica/efeitos dos fármacos , Salmonella enteritidis/efeitos dos fármacos , Temperatura Baixa , Temperatura Alta , Concentração de Íons de Hidrogênio , Cloreto de Sódio
16.
Acta Otolaryngol ; 139(2): 146-152, 2019 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-30734622

RESUMO

BACKGROUND: Clinical trials of cell-based therapies using induced pluripotent stem (iPS) cells have already been started for several neurological diseases. OBJECTIVE: The purpose of the present study was to explore the characteristics and differentiation of somatic cells in vitro undergoing a low pH treatment, so as to provide new therapeutic strategies for treating sensorineural hearing loss. METHODS: Somatic cells were treated with low pH solution to alter their characteristics. In addition, a mouse model of the cochlear lesion was constructed using bilirubin. Subsequently, the characteristics and therapeutic effect of somatic cells undergoing low pH treatment were examined by morphology, alkaline phosphatase (AKP) activity, immunofluorescence assay and q-PCR. RESULTS: The cells in the experimental group grew better than those in the control group. The AKP activity in the experimental group was higher than that in the control group. The expression of Nanog and Oct4 was both positive in the two groups. When the cells were changed to neurobasal medium, the marker of nestin was positive. CONCLUSION: The human somatic cells undergoing a low pH treatment showed the similar characteristics as those of iPS cells, although the functions and therapeutic effect of these altered human somatic cells need to be further studied.


Assuntos
Ácidos/farmacologia , Células-Tronco Adultas/efeitos dos fármacos , Cóclea/citologia , Perda Auditiva Neurossensorial/terapia , Células-Tronco Pluripotentes Induzidas/transplante , Transplante de Células-Tronco/métodos , Células-Tronco Adultas/citologia , Células-Tronco Adultas/transplante , Animais , Diferenciação Celular/fisiologia , Células Cultivadas , Modelos Animais de Doenças , Feminino , Perda Auditiva Neurossensorial/fisiopatologia , Humanos , Células-Tronco Pluripotentes Induzidas/efeitos dos fármacos , Camundongos , Distribuição Aleatória , Reação em Cadeia da Polimerase em Tempo Real , Medição de Risco , Sensibilidade e Especificidade
17.
Biochimie ; 160: 46-54, 2019 May.
Artigo em Inglês | MEDLINE | ID: mdl-30763640

RESUMO

Bacterial survive and respond to adverse changes in the environment by regulating gene transcription through two-component regulatory systems. In Salmonella Typhimurium the STM1485 gene expression is induced under low pH (4.5) during replication inside the epithelial host cell, but it is not involved in sensing or resisting to this condition. Since the RcsCDB system is activated under acidic conditions, we investigated whether this system is able to modulate STM1485 expression. We demonstrated that acid-induced activation of the RcsB represses STM1485 transcription by directly binding to the promoter. Under the same condition, the RstA regulator activates the expression of this gene. Physiologically, we observed that RcsB-dependent repression is required for the survival of bacteria when they are exposed to pancreatic fluids. We hypothesized that STM1485 plays an important role in Salmonella adaptation to pH changes, during transition in the gastrointestinal tract. We suggest that bacteria surviving the gastrointestinal environment invade the epithelial cells, where they can remain in vacuoles. In this new environment, acidity and magnesium starvation activate the expression of the RstA regulator in a PhoPQ-dependent manner, which in turn induces STM1485 expression. These levels of STM1485 allow increased bacterial replication within vacuoles to continue the course of infection.


Assuntos
Ácidos/farmacologia , Proteínas de Bactérias/genética , Proteínas de Bactérias/metabolismo , Regulação Bacteriana da Expressão Gênica/efeitos dos fármacos , Salmonella typhimurium/metabolismo , Fatores de Transcrição/metabolismo , Transcrição Genética , Sequência de Bases , Trato Gastrointestinal/efeitos dos fármacos , Trato Gastrointestinal/microbiologia , Viabilidade Microbiana , Regiões Promotoras Genéticas , Elementos Reguladores de Transcrição , Salmonella typhimurium/efeitos dos fármacos , Salmonella typhimurium/genética , Transdução de Sinais , Fatores de Transcrição/genética
18.
Curr Microbiol ; 76(4): 448-461, 2019 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-30778660

RESUMO

Probiotics are well known for their wide range of beneficial activities. However, recent use of probiotic Bifidobacterium, Enterococcus, and Lactobacillus spp. has been plagued by certain disadvantages such as complex growth requirements, high maintenance cost, susceptibility to the gastrointestinal environment, pathogenic gene transfer, non-standardized dosage, cell lysis at extreme acidic pH, widespread antibiotic resistance, and lower bacterial viability due to the lack of spore formation. Therefore, spore-forming bacteria belonging to Sporosarcina genus such as pasteurii, globispora, and psychrophila were assessed for probiotic characteristics such as biofilm formation, intestinal adhesion, acid and bile tolerance, antibiotic sensitivity, and anti-pathogenic activity. This ensures bacterial viability under gastrointestinal conditions and enabled the same to colonize effectively in the intestinal lumen (in vitro). The bacterial cell counts ranging from 6.59 to 6.91 log(CFU/mL) was observed for Sporosarcina spp. after 16 h. This indicated that there is no significant difference in the cell counts (P-value = 0.90). The cell counts of Sporosarcina spp. ranging from 5.57 to 5.93 log(CFU/mL) displayed strong acid tolerance at pH 2. They were also viable at higher bile (0.5%) concentration. Among the Sporosarcina spp., pasteurii showed better tolerance (6.90 log(CFU/mL)) even after 16 h. Among the selected bacteria, Sporosarcina psychrophila was more susceptible to teicoplanin and meropenem with an inhibition zone of 30 mm. Maximum antagonistic activity was observed against Serratia marcescens (with inhibition zone up to 15 mm). Our results suggest that bacteria belonging to Sporosarcina genus possess all the required characteristics to be used as potential poultry probiotics.


Assuntos
Aves Domésticas/microbiologia , Probióticos , Sporosarcina/fisiologia , Ácidos/farmacologia , Animais , Antibacterianos/farmacologia , Bactérias/efeitos dos fármacos , Aderência Bacteriana , Fenômenos Fisiológicos Bacterianos , Ácidos e Sais Biliares/farmacologia , Biofilmes/crescimento & desenvolvimento , Testes de Sensibilidade Microbiana , Viabilidade Microbiana , Sporosarcina/efeitos dos fármacos , Sporosarcina/crescimento & desenvolvimento
19.
J Biosci Bioeng ; 128(1): 8-12, 2019 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-30709704

RESUMO

Bioproduction of organic acids under low pH condition without adding inducer and neutralizer is an economical craft to decrease downstream cost. Candida glycerinogenes had higher tolerances to low pH and lactic acid than Saccharomyces cerevisiae. QRT-PCR analysis showed that four of fifteen candidates functioned as potentially acid-inducible promoters in C. glycerinogenes. In particular, PCggmt1 showed the strongest induction ability at pH 2.5. Fluorescence analysis indicated that the induction ability of PCggmt1 gradually increased as the pH decreased. In addition, PCggmt1 had the binding sites of Msn2p/4p, Azf1p, and Nrg1p. PCggmt1 was further used to control the expression of lactate dehydrogenase gene from Rhizopus oryzae in C. glycerinogenes. Compared with pH 5.5, the specific activity of lactate dehydrogenase and lactic acid titer at pH 2.5 were increased by 229% and 218%, reaching 13.8 mU/mg and 12.3 g/L, respectively. These results presented here showed a potential to produce organic acid economically at low pH by the stress tolerant C. glycerinogenes and the novel low-pH inducible promoter PCggmt1.


Assuntos
Ácidos/farmacologia , Candida , L-Lactato Desidrogenase/genética , Ácido Láctico/biossíntese , Engenharia Metabólica/métodos , Regiões Promotoras Genéticas/efeitos dos fármacos , Candida/genética , Candida/metabolismo , Clonagem Molecular/métodos , Tolerância a Medicamentos/genética , Regulação Enzimológica da Expressão Gênica/efeitos dos fármacos , Regulação Fúngica da Expressão Gênica/efeitos dos fármacos , Concentração de Íons de Hidrogênio , L-Lactato Desidrogenase/metabolismo , Ácido Láctico/metabolismo , Ácido Láctico/farmacologia , Rhizopus/genética , Rhizopus/metabolismo , Ativação Transcricional/efeitos dos fármacos
20.
Appl Biochem Biotechnol ; 188(3): 706-719, 2019 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-30680701

RESUMO

Clavulanic acid (CA) is frequently prescribed for treatment of bacterial infections. Despite the large number of studies concerning CA production, there is still a need to search for more effective and productive processes because it is mainly produced by biochemical route and is chemically unstable. This paper evaluates the influence of acid and cold stresses on CA production by Streptomyces clavuligerus in bench scale stirred tank bioreactor. Four batch cultures were conducted at constant pH (6.8 or 6.3) and temperature (30, 25, or 20 °C) and five batch cultures were performed with application of acid stress (pH reduction from 6.8 to 6.3), cold stress (reduction from 30 to 20 °C), or both. The highest maximum CA concentration (684.4 mg L-1) was obtained in the culture conducted at constant temperature of 20 °C. However, the culture under acid stress, in which the pH was reduced from 6.8 to 6.3 at a rate of 0.1 pH unit every 6 h, provided the most promising result, exhibiting a global yield coefficient of CA relative to cell formation (YCA/X) of 851.1 mgCA gX-1. High YCA/X values indicate that a small number of cells are able to produce a large amount of antibiotic with formation of smaller amounts of side byproducts. This could be especially attractive for decreasing the complexity and cost of the downstream processing, enhancing CA production.


Assuntos
Ácidos/farmacologia , Ácido Clavulânico/biossíntese , Temperatura Baixa , Streptomyces/metabolismo , Estresse Fisiológico , Técnicas de Cultura Celular por Lotes , Reatores Biológicos , Meios de Cultura , Fermentação , Concentração de Íons de Hidrogênio , Streptomyces/efeitos dos fármacos , Streptomyces/fisiologia , Inibidores de beta-Lactamases/metabolismo
SELEÇÃO DE REFERÊNCIAS
DETALHE DA PESQUISA