RESUMO
Histamine food poisoning is a major safety concern related to seafood consumption worldwide. Morganella psychrotolerans is a novel psychrotolerant histamine-producer. In this study, the histamine production behaviors of M. psychrotolerans and two other major histamine-producers, mesophilic Morganella morganii and psychrotrophic Photobacterium phosphoreum, were compared in seafood products, and histamine accumulation by M. psychrotolerans was characterized at various pH and temperature levels in culture broth. The growth of M. psychrotolerans and P. phosphoreum increased similarly at 4 °C in canned tuna, but M. psychrotolerans produced much higher levels of histamine than P. phosphoreum. Histamine accumulation by M. psychrotolerans was induced at lower environmental pH condition at 4 and 20 °C. The optimal temperature and pH for producing histamine by crude histidine decarboxylase of M. psychrotolerans were 30 °C and pH 7, respectively. The activity of the crude HDC extracted from M. psychrotolerans cells at 10 °C retained 45% of the activity at 30 °C. Histidine decarboxylase gene expression of M. psychrotolerans was induced by low pH conditions. These results suggest that M. psychrotolerans are also a very important histamine-producer leading to histamine poisoning associated with seafood below the refrigeration temperature.
Assuntos
Histamina/biossíntese , Morganella/metabolismo , Alimentos Marinhos/análise , Alimentos Marinhos/microbiologia , Temperatura , Atum/microbiologia , Animais , Qualidade de Produtos para o Consumidor , Meios de Cultura/química , Doenças Transmitidas por Alimentos/microbiologia , Histidina Descarboxilase/genética , Concentração de Íons de Hidrogênio , Morganella/genética , Morganella morganii/metabolismo , Photobacterium/metabolismoRESUMO
In this study, simulations are conducted using a network model to examine how the macroscopic network in the brain is related to the complexity of activity for each region. The network model is composed of multiple neuron groups, each of which consists of spiking neurons with different topological properties of a macroscopic network based on the Watts and Strogatz model. The complexity of spontaneous activity is analyzed using multiscale entropy, and the structural properties of the network are analyzed using complex network theory. Experimental results show that a macroscopic structure with high clustering and high degree centrality increases the firing rates of neurons in a neuron group and enhances intraconnections from the excitatory neurons to inhibitory neurons in a neuron group. As a result, the intensity of the specific frequency components of neural activity increases. This decreases the complexity of neural activity. Finally, we discuss the research relevance of the complexity of the brain activity.
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Dental plaque biofilms cause various dental diseases; therefore, inhibiting the growths of the dental plaque bacteria which produce biofilms can be a strategy for preventing dental disease. Certain sulfated polysaccharides from marine algae exert antimicrobial activities against human bacterial pathogens in addition to their physiological benefits. On the basis of these observations, the antimicrobial and antibiofilm activities of sulfated polysaccharides from different marine algae were evaluated against dental plaque bacteria. Among the sulfated polysaccharides, a fucoidan from Fucus vesiculosus showed notable antimicrobial activities against the selected dental plaque bacteria, including some foodborne pathogenic bacteria. The minimum inhibitory concentrations were of 125 to 1000 µg mL-1. Regarding the antibiofilm activity, the fucoidan at the concentrations of above 250 µg mL-1 completely suppressed the biofilm formations and planktonic cell growths of Streptococcus mutans and S. sobrinus. However, no eliminative effect on the completed biofilm was observed. The fucoidan consisted of almost fucose base polysaccharide containing approximately 14.0% sulfate content. The average molecular weight of the fucoidan was changed by heat treatment (121 °C for 15 min) and it affected the antimicrobial activity.
Assuntos
Antibacterianos/farmacologia , Biofilmes/efeitos dos fármacos , Placa Dentária/tratamento farmacológico , Fucus/química , Polissacarídeos/farmacologia , Antibacterianos/química , Antibacterianos/isolamento & purificação , Antibacterianos/uso terapêutico , Organismos Aquáticos/química , Placa Dentária/microbiologia , Avaliação Pré-Clínica de Medicamentos , Humanos , Testes de Sensibilidade Microbiana , Polissacarídeos/química , Polissacarídeos/isolamento & purificação , Polissacarídeos/uso terapêutico , Streptococcus mutans/efeitos dos fármacos , Streptococcus mutans/fisiologia , Streptococcus sobrinus/efeitos dos fármacos , Streptococcus sobrinus/fisiologia , Ésteres do Ácido Sulfúrico/químicaRESUMO
This study examined changes in self-reported stress symptoms after instruction in the Transcendental Meditation(®) technique among 171 residents of two cities (Sendai and Ishinomaki) directly affected by the 2011 Japan earthquake and tsunami disaster compared with 326 non-disaster Tokyo participants previously tested before and after learning the technique and a no-treatment control group (n = 68). The participants completed a rating checklist of mental and physical symptoms. Disaster area participants who learned the Transcendental Meditation(®) technique in contrast to controls showed a significant drop in total symptom score from pre-test to post-test (effect size = -1.09). Results were comparable for an ordinal measure of symptom intensity. The findings suggest the potential value of this procedure for relief from disaster trauma.
Assuntos
Desastres , Meditação/métodos , Transtornos de Estresse Pós-Traumáticos/terapia , Adulto , Terremotos , Feminino , Humanos , Japão , Masculino , Resultado do Tratamento , TsunamisRESUMO
Understanding how the structural organization of neural networks influences their computational capabilities is of great interest to both machine learning and neuroscience communities. In our previous work, we introduced a novel learning system, called the reservoir of basal dynamics (reBASICS), which features a modular neural architecture (small-sized random neural networks) capable of reducing chaoticity of neural activity and of producing stable self-sustained limit cycle activities. The integration of these limit cycles is achieved by linear summation of their weights, and arbitrary time series are learned by modulating these weights. Despite its excellent learning performance, interpreting a modular structure of isolated small networks as a brain network has posed a significant challenge. Here, we investigate how local connectivity, a well-known characteristic of brain networks, contributes to reducing neural system chaoticity and generates self-sustained limit cycles based on empirical experiments. Moreover, we present the learning performance of the locally connected reBASICS in two tasks: a motor timing task and a learning task of the Lorenz time series. Although its performance was inferior to that of modular reBASICS, locally connected reBASICS could learn a time series of tens of seconds while the time constant of neural units was ten milliseconds. This work indicates that the locality of connectivity in neural networks may contribute to generation of stable self-sustained oscillations to learn arbitrary long-term time series, as well as the economy of wiring cost.
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Excitatory and inhibitory neurons are fundamental components of the brain, and healthy neural circuits are well balanced between excitation and inhibition (E/I balance). However, it is not clear how an E/I imbalance affects the self-organization of the network structure and function in general. In this study, we examined how locally altered E/I balance affects neural dynamics such as the connectivity by activity-dependent formation, the complexity (multiscale entropy) of neural activity, and information transmission. In our simulation, a spiking neural network model was used with the spike-timing dependent plasticity rule to explore the above neural dynamics. We controlled the number of inhibitory neurons and the inhibitory synaptic weights in a single neuron group out of multiple neuron groups. The results showed that a locally increased E/I ratio strengthens excitatory connections, reduces the complexity of neural activity, and decreases information transmission between neuron groups in response to an external input. Finally, we argued the relationship between our results and excessive connections and low complexity of brain activity in the neuropsychiatric brain disorders.
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The ability of the brain to generate complex spatiotemporal patterns with specific timings is essential for motor learning and temporal processing. An approach that can model this function, using the spontaneous activity of a random neural network (RNN), is associated with orbital instability. We propose a simple system that learns an arbitrary time series as the linear sum of stable trajectories produced by several small network modules. New finding in computer experiments is that the trajectories of the module outputs are orthogonal to each other. They created a dynamic orthogonal basis acquiring a high representational capacity, which enabled the system to learn the timing of extremely long intervals, such as tens of seconds for a millisecond computation unit, and also the complex time series of Lorenz attractors. This self-sustained system satisfies the stability and orthogonality requirements and thus provides a new neurocomputing framework and perspective for the neural mechanisms of motor learning.
Assuntos
Aprendizagem , Redes Neurais de Computação , Encéfalo , Rede Nervosa , Fatores de TempoRESUMO
People tend to expect mental capabilities in a robot based on anthropomorphism and often attribute the cause and responsibility for a failure in human-robot interactions to the robot. This study investigated the relationship between mind perception, a psychological scale of anthropomorphism, and attribution of the cause and responsibility in human-robot interactions. Participants played a repeated noncooperative game with a human, robot, or computer agent, where their monetary rewards depended on the outcome. They completed questionnaires on mind perception regarding the agent and whether the participant's own or the agent's decisions resulted in the unexpectedly small reward. We extracted two factors of Experience (capacity to sense and feel) and Agency (capacity to plan and act) from the mind perception scores. Then, correlation and structural equation modeling (SEM) approaches were used to analyze the data. The findings showed that mind perception influenced attribution processes differently for each agent type. In the human condition, decreased Agency score during the game led to greater causal attribution to the human agent, consequently also increasing the degree of responsibility attribution to the human agent. In the robot condition, the post-game Agency score decreased the degree of causal attribution to the robot, and the post-game Experience score increased the degree of responsibility to the robot. These relationships were not observed in the computer condition. The study highlights the importance of considering mind perception in designing appropriate causal and responsibility attribution in human-robot interactions and developing socially acceptable robots.
Assuntos
Robótica , Humanos , Comportamento Social , Emoções , Percepção Social , RecompensaRESUMO
The integrated gradients (IG) method is widely used to evaluate the extent to which each input feature contributes to the classification using a deep learning model because it theoretically satisfies the desired properties to fairly attribute the contributions to the classification. However, this approach requires an appropriate baseline to do so. In this study, we propose a compensated IG method that does not require a baseline, which compensates the contributions calculated using the IG method at an arbitrary baseline by using an example of the Shapley sampling value. We prove that the proposed approach can compute the contributions to the classification results reliably if the processes of each input feature in a classifier are independent of one another and the parameterization of each process is identical, as in shared weights in convolutional neural networks. Using three datasets on electroencephalogram recordings, we experimentally demonstrate that the contributions obtained by the proposed compensated IG method are more reliable than those obtained using the original IG method and that its computational complexity is much lower than that of the Shapley sampling method.
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Shiga toxin-producing Escherichia coli and Salmonella enterica are important pathogens worldwide. Bacteriophages can be effectively used to reduce the incidence of foodborne pathogens. The host recognition systems of phages are highly specific, with the host range of a common phage being limited to the species or strain level. Here, we characterized a novel broad-host-range phage, EscoHU1, that infects several bacterial species, including E. coli and S. enterica, and evaluated its antimicrobial potential to inhibit E. coli O157:H7 and S. Typhimurium growth in food systems. The adsorption of EscoHU1 on E. coli was faster than that on S. Typhimurium; however, the one-step growth curves of EscoHU1 in both species were similar. Genomic analysis of EscoHU1 revealed that this phage has long direct terminal repeats at both ends of the genome, and phylogenetic analysis of the terminase large subunit confirmed that EscoHU1 belongs to the genus Epseptimavirus. Comparative analysis of structural proteins indicated a diversity of proteins related to the host range (receptor-binding proteins and L-shaped tail fibers). Challenge tests using beef and milk demonstrated the antimicrobial effects of EscoHU1 in inhibiting the growth of E. coli O157:H7 and S. Typhimurium in the food system. However, the antimicrobial effect of EscoHU1 on S. Typhimurium was lower than that on E. coli O157:H7. These results suggest that the novel broad-host-range phage EscoHU1 may serve as an effective antimicrobial agent to reduce food poisoning caused by E. coli O157:H7 and S. Typhimurium.
Assuntos
Bacteriófagos , Escherichia coli O157 , Salmonella enterica , Animais , Bacteriófagos/genética , Bovinos , Microbiologia de Alimentos , Inocuidade dos Alimentos , Genômica , Especificidade de Hospedeiro , FilogeniaRESUMO
Nine different combinations of mugi koji (barley steamed and molded with Aspergillus oryzae) and halotolerant microorganisms (HTMs), Zygosaccharomyces rouxii, Candida versatilis, and Tetragenococcus halophilus, were inoculated into chum salmon sauce mash under a non-aseptic condition used in industrial fish sauce production and fermented at 35 +/- 2.5 degrees C for 84 days to elucidate the microbial dynamics (i.e., microbial count and microbiota) during fermentation. The viable count of halotolerant yeast (HTY) in fermented chum salmon sauce (FCSS) mash showed various time courses dependent on the combination of the starter microorganisms. Halotolerant lactic acid bacteria (HTL) were detected morphologically and physiologically only from FCSS mash inoculated with T. halophilus alone or with T. halophilus and C. versatilis during the first 28 days of fermentation. Only four fungal species, Z. rouxii, C. versatilis, Pichia guilliermondii, and A. oryzae, were detected throughout the fermentation by PCR-denaturing gradient gel electrophoresis (PCR-DGGE). In FCSS mash, dominant HTMs, especially eumycetes, were nonexistent. However, under the non-aseptic conditions, undesirable wild yeast such as P. guilliermondii grew fortuitously. Therefore, HTY inoculation into FCSS mash at the beginning of fermentation is effective in preventing the growth of wild yeast and the resultant unfavorable flavor.
Assuntos
Candida/isolamento & purificação , Contagem de Colônia Microbiana/métodos , Enterococcaceae/isolamento & purificação , Oncorhynchus keta/microbiologia , Alimentos Marinhos/microbiologia , Zygosaccharomyces/isolamento & purificação , Animais , Candida/classificação , Candida/genética , Eletroforese em Gel de Ágar , Enterococcaceae/classificação , Enterococcaceae/genética , Fermentação , Microbiologia de Alimentos , Humanos , Pichia/classificação , Pichia/genética , Pichia/isolamento & purificação , Reação em Cadeia da Polimerase , Dinâmica Populacional , Zygosaccharomyces/classificação , Zygosaccharomyces/genéticaRESUMO
Histamine (scombroid) poisoning is a foodborne illness caused by ingestion of histamine-contaminated seafood; therefore, inhibition of the growth of histamine-producing bacteria is key for it prevention. Infection of pathogenic bacteria by bacteriophages (phages) is being developed to prevent multiple foodborne illnesses. Here, we describe the inhibitory effect of a phage mixture on growth and histamine accumulation of Morganella morganii subsp. morganii, the primary causative agent of histamine poisoning in fish meat. We isolated novel two phages, ΦMV-1 and ΦMV-4, which infected M. morganii subsp. morganii strains tested in this study. ΦMV-1 and ΦMV-4 belong to family Myoviridae. Pulsed-field gel electrophoresis revealed that these phages are jumbo bacteriophages with large genomes. The latent period, rise period and burst size of ΦMV-1 were 30 min, 60 min, and 224 PFU per infected cell, respectively, and those of ΦMV-4 were 60 min, 50 min, and 62 PFU per infected cell, respectively. A mixture of ΦMV-1 and ΦMV-4 effectively prevented regrowth of M. morganii subsp. morganii after phage treatment, suggesting that the phage mixture treatment is more effective for inhibition of growth and histamine accumulation by M. morganii subsp. morganii than single phage treatment. Treatment with phage mixture inhibited growth and histamine accumulation by M. morganii subsp. morganii in canned and fresh tuna. The phage mixture might be an effective way to prevent growth of the histamine producer and accumulation of histamine in seafood.
Assuntos
Antibiose/fisiologia , Doenças Transmitidas por Alimentos/prevenção & controle , Histamina/metabolismo , Morganella morganii/crescimento & desenvolvimento , Myoviridae/metabolismo , Animais , Peixes/microbiologia , Alimentos Marinhos/microbiologia , Atum/microbiologiaRESUMO
Cortical neural connectivity has been shown to exhibit a small-world (SW) network topology. However, the role of the topology in neural information processing remains unclear. In this study, we investigated the learning performance of an echo state network (ESN) that includes the SW topology as a reservoir. To elucidate the potential of the SW topology, we limited the numbers of the input and output nodes in the ESN and spatially segregated the output nodes from the input nodes. We tested the ESNs in two benchmark tasks: memory capacity and nonlinear time-series prediction. The SW-ESN exhibited the best learning performance when the spectral radius of the weight matrix was large and when the input and output nodes were segregated. That is, the SW topology provided the ESN with a stable echo state property over a broad range of the weight matrix and efficiently propagated input signals to the output nodes. This result is the same as that of the ESN using a real human cortical connectivity. Thus, the results suggest that the SW topology is essential for maintaining the echo state property, which is the appropriate neural dynamics between input and output brain regions.
Assuntos
Encéfalo/fisiologia , Conectoma , Redes Neurais de Computação , Humanos , Memória/fisiologia , Dinâmica não LinearRESUMO
The main objective of this study was to evaluate the effect of two commonly used essential oils after treatment with anodic electrolyzed NaCl solution in order to extend the shelf life of coated semifried tuna slices. Samples of tuna slices were treated with 100-fold electrolyzed water and coated with an edible solution containing 1% essential oil (0.5% eugenol [E] plus 0.5% linalool [L]). The coated slices were fried at 170 degrees C for 1 min and then stored at 5 and 25 degrees C. Total volatile basic nitrogen of slices treated with electrolyzed water and 1% (E+L) decreased from 15.5 for the nontreated control slices to 9.7 immediately after treatment and remained at a low level (<30) until the end of the storage period (day 20). Treatment with 1% (E+L) significantly suppressed lipid oxidation in coated semifried tuna. Sensory evaluation and microbiological assays showed that treatment with electrolyzed water and 1% (E+L) extended the shelf life of coated semifried slices to 15 and 2 days compared with 5 and 1 days for control slices during storage at 5 and 25 degrees C, respectively.
Assuntos
Manipulação de Alimentos/métodos , Conservação de Alimentos/métodos , Conservantes de Alimentos/farmacologia , Óleos Voláteis/farmacologia , Alimentos Marinhos/microbiologia , Cloreto de Sódio/farmacologia , Atum/microbiologia , Animais , Contagem de Colônia Microbiana , Qualidade de Produtos para o Consumidor , Relação Dose-Resposta a Droga , Eletrólise , Microbiologia de Alimentos , Humanos , Alimentos Marinhos/normas , Paladar , Temperatura , Fatores de TempoRESUMO
The antimicrobial and antioxidant effects on carp fillet samples of treatments with alkaline electrolyzed NaCl solution EW (-) prior to treatment with acidic electrolyzed NaCl solution EW (+) and 1% solutions of the essential oils consisting of 0.5% carvacrol and 0.5% thymol (1% Cv+Ty) were tested. First carp fillet samples were treated with EW (-), then EW (+), followed by 1% (C+T), represented as [EW (-)/EW (+)/1% (Cv+Ty)] for 15 min, during drying at 45 degrees C. Samples were subsequently evaluated by microbiological, chemical and sensory analyses. Microbiological analyses indicated that the initial total microbial counts of samples treated with EW (-)/EW (+), 1% (Cv+Ty) or EW (-)/EW (+)/1% (Cv+Ty) were significantly (p< or =0.05) reduced, compared with the control sample. Treatment with EW (-)/EW (+)/1% (Cv+Ty) gave the strongest overall inhibition of microbial growth when compared to all of the other treatments. The volatile basic nitrogen (VBN) value of samples treated with EW (-)/EW (+)/1% (Cv+Ty) was kept at low level (18.46+/-0.45) until the end of drying period (5 days), compared with control samples (40.33+/-0.58). Treatment with EW (-)/EW (+)/1% (Cv+Ty) during drying significantly reduced the peroxide values (PV) and thiobarbituric acid values (TBA). Sensory evaluation indicated that there were significant differences (p< or =0.05) in the color, odor, taste, flavor and texture, on the end of the 5-day drying period between samples treated with EW (-)/EW (+)/1% (Cv+Ty), as compared to all of the other treatments. We conclude that treatment with EW (-)/EW (+)/1% (Cv+Ty) had stronger antimicrobial and antioxidant effects than all of the other treatments on carp fillets during drying, and could be a good alternative to artificial preservatives in food industry.
Assuntos
Carpas/microbiologia , Manipulação de Alimentos/métodos , Conservação de Alimentos/métodos , Conservantes de Alimentos/farmacologia , Alimentos Marinhos/microbiologia , Animais , Contagem de Colônia Microbiana , Qualidade de Produtos para o Consumidor , Relação Dose-Resposta a Droga , Sinergismo Farmacológico , Eletrólise , Microbiologia de Alimentos , Humanos , Óleos Voláteis/farmacologia , Pigmentação , Alimentos Marinhos/normas , Cloreto de Sódio/farmacologia , Paladar , Fatores de TempoRESUMO
The antimicrobial compounds against the fish pathogen Photobacterium damselae subsp. piscicida were isolated from Polygonum sachalinense rhizomes. The structures of the antimicrobial compounds 1 and 2 were determined by 1H and 13C NMR, 2D-NMR (COSY, HSQC, HMBC and ROESY) and FAB-MS to be phenylpropanoid glycosides, vanicoside A and B, respectively. Both compounds have feruloyl and p-coumaroyl groups bonded to a sucrose moiety in their structures. Vanicoside A also has an acetyl group in the sucrose moiety. The MIC values for vanicoside A and B against Ph. damselae subsp. piscicida DPp-1 were 32 and 64 microg/ml, respectively. The antimicrobial activities of these vanicosides were modest, in contrast to higher activities (MICs at < 4 microg/ml) of antibiotics, florphenicol, ampicillin and amoxicillin, which have been generally used for treating pasteurellosis. The activities of the vanicosides, however, were higher than those (MICs at 256 microg/ml) of ferulic acid and p-coumaric acid. It was suggested that the structure of phenylpropanoids esterified with sucrose was essential for higher antimicrobial activity of vanicosides and also acetylation of sucrose might affect the activity against the bacterium.
Assuntos
Anti-Infecciosos/isolamento & purificação , Cinamatos/farmacologia , Photobacterium/efeitos dos fármacos , Polygonum/química , Animais , Anti-Infecciosos/química , Anti-Infecciosos/farmacologia , Cinamatos/química , Cinamatos/isolamento & purificação , Doenças dos Peixes/microbiologia , Peixes/microbiologia , Rim/microbiologia , Espectroscopia de Ressonância Magnética , Testes de Sensibilidade Microbiana , Photobacterium/isolamento & purificação , Extratos Vegetais/química , Extratos Vegetais/isolamento & purificação , Extratos Vegetais/farmacologia , Proteína Quinase C/antagonistas & inibidores , Rizoma/químicaRESUMO
An open-tubular capillary chromatography system (tube radial distribution chromatography, TRDC) was developed using a ternary solvent (water-acetonitrile-ethyl acetate; volume ratio, 3:8:4) containing 10 mmol L(-1) 8-quinolinol for the separation of nitrate, chloride, and sulfate compounds of Ni(II), Al(III), and Fe(III). When a mixed solution of the Ni(II) compounds was injected into an untreated fused-silica capillary tube (90 cm × 75 µm i.d.) with a ternary solvent flow rate of 0.8 µL min(-1), the compounds were eluted in the following order: [Ni(II)-(8-quinolinol)3] complex, [Ni(II)-(8-quinolinol)]-nitrate ion interaction complex, [Ni(II)-(8-quinolinol)]-chloride ion interaction complex, and [Ni(II)-(8-quinolinol)]-sulfate ion interaction complex. The elution of mixtures of the Al(III) and Fe(III) compounds showed similar trends.
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Strain CS526 was isolated from frozen surimi and identified as a bacteriocin producer that had strong inhibitory activity against Listeria monocytogenes. Strain CS526 was identified as Carnobacterium piscicola by partial 16S rDNA sequence similarity. The ability of this bacteriocinogenic strain and nonbacteriocinogenic C. piscicola JCM5348 to inhibit the growth of L. monocytogenes was examined in culture broth incubated at 12 degrees C and cold-smoked salmon stored at 4, 12, and 20 degrees C. L. monocytogenes viable counts in the culture broth rapidly declined from 10(6) colony-forming units per ml to less than 10 colony-forming units per ml within 1 day at 12 degrees C in the presence of C. piscicola CS526. At 4 and 12 degrees C, inhibition of L. monocytogenes on salmon depended on the initial inoculum level of C. piscicola CS526. However, C. piscicola CS526 was bactericidal to L. monocytogenes within 21 and 12 days at 4 and 12 degrees C in cold-smoked salmon, respectively, even when the initial inoculum levels were low. C. piscicola CS526 suppressed the maximum cell number of L. monocytogenes by two and three log cycles, even at 20 degrees C. However, C. piscicola JCM5348 did not prevent the growth of the pathogen, except at 4 degrees C. Bacteriocin was detected in the samples coinoculated with C. piscicola CS526. The study shows that C. piscicola CS526 might have potential for biopreservation of refrigerated foods against L. monocytogenes.
Assuntos
Bacteriocinas/farmacologia , Produtos Pesqueiros/microbiologia , Manipulação de Alimentos/métodos , Lactobacillaceae/fisiologia , Listeria monocytogenes/crescimento & desenvolvimento , Salmão/microbiologia , Animais , Antibiose , Bacteriocinas/biossíntese , Contagem de Colônia Microbiana , Microbiologia de Alimentos , Embalagem de Alimentos , Conservação de Alimentos/métodos , Lactobacillaceae/metabolismo , Temperatura , Fatores de TempoRESUMO
Morganella morganii has been identified as a causative agent of opportunistic infections and histamine poisoning. Bacteriophage is a virus and has recently been considered an alternative agent to antibiotics for the control of bacteria that have developed antibiotic resistance. In this study, a novel M. morganii bacteriophage isolated from river water was characterized. The isolated phage, termed FSP1, was purified by polyethylene glycol precipitation followed by cesium chloride density-gradient centrifugation. FSP1 has infectivity against only M. morganii and was identified as a Myoviridae bacteriophage through morphological analysis with transmission electron microscopy. According to the one-step growth curve, the FSP1 latent period, eclipse period, and burst size were 30, 20 min, and 42 PFU infected cell(-1) , respectively. The genome size of FSP1 was estimated to be c. 45.6-49.4 kb by restriction endonuclease analyses. Moreover, challenge testing against M. morganii in vitro revealed that FSP1 had high lytic activity and that the viable cell count of M. morganii was reduced by 6.12 log CFU mL(-1) after inoculation with FSP1 at a multiplicity of infection (MOI) = 10. These results suggested that FSP1 could be used as a biocontrol agent against M. morganii for treatment of infectious disease treatment or food decontamination.
Assuntos
Morganella morganii/virologia , Myoviridae/isolamento & purificação , Rios/virologia , Bacteriólise , Genoma Viral , Myoviridae/classificação , Myoviridae/fisiologia , Myoviridae/ultraestruturaRESUMO
Chum salmon sauce mash was inoculated with barley koji (barley steamed and molded with Aspergillus oryzae ) and halotolerant microorganisms (HTMs), Zygosaccharomyces rouxii , Candida versatilis , and Tetragenococcus halophilus , in nine different combinations under non-aseptic conditions similar to the industrial fish sauce production and fermented at 35 +/- 2.5 degrees C for 84 days. The changes in the chemical components, color, and sensory properties during fermentation were investigated. Free amino acid content was increased, and the browning of fish sauce was enhanced by the usage of barley koji during fermentation. The halotolerant yeast (HTY) produced ethanol and repressed the browning by consumption of reducing sugar. Inoculated Z. rouxii in the fish sauce mash produced 2-phenylethanol (2-PE) and 4-hydoxy-2(or 5)-ethyl-5(or 2)-methyl-3(2H)-furanone (HEMF), and C. versatilis in the fish sauce mash produced 4-ethylguaiacol (4-EG), known as characteristic flavor compounds in soy sauce, adding soy-sauce-like flavor to the fish sauce. Thus, inoculation of HTMs and barley koji was effective for conferring the soy-sauce-like flavor and increasing free amino acid and ethanol contents in fish sauce product.