scholarly journals Changes in Listeria monocytogenes Membrane Fluidity in Response to Temperature Stress

2007 ◽  
Vol 73 (20) ◽  
pp. 6429-6435 ◽  
Author(s):  
Mohamed Badaoui Najjar ◽  
Michael Chikindas ◽  
Thomas J. Montville
Keyword(s):  
Listeria Monocytogenes ◽  
Membrane Fluidity ◽  
The Other ◽  
Sensitive Mutant ◽  
Homeoviscous Adaptation ◽  
Whole Cells ◽  
Food Borne ◽  
Cold Sensitive ◽  
The Difference ◽  
Response To Temperature

ABSTRACT Listeria monocytogenes is a food-borne pathogen that has been implicated in many outbreaks associated with ready-to-eat products. Listeria adjusts to various stresses by adjusting its membrane fluidity, increasing the uptake of osmoprotectants and cryoprotectants, and activating the σB stress factor. The present work examines the regulation of membrane fluidity through direct measurement based on fluorescent anisotropy. The membrane fluidities of L. monocytogenes Scott A, NR30, wt10403S, and cld1 cells cultured at 15 and 30°C were measured at 15 and 30°C. The membrane of the cold-sensitive mutant (cld1) was more rigid than the membranes of the other strains when grown at 30°C, but when grown at 15°C, it was able to adjust its membrane to approach the rigidity of the other strains. The difference in rigidities, as determined at 15 and 30°C, was greater in liposomes than in whole cells. The rates of fluidity adjustment and times required for whole cells to adjust to a different temperature were similar among strains but different from those of liposomes. This suggests that the cells had a mechanism for homeoviscous adaptation that was absent in liposomes.

scholarly journals Comparative Intracellular (THP-1 Macrophage) and Extracellular Activities of β-Lactams, Azithromycin, Gentamicin, and Fluoroquinolones against Listeria monocytogenes at Clinically Relevant Concentrations

2002 ◽  
Vol 46 (7) ◽  
pp. 2095-2103 ◽  
Author(s):  
Stéphane Carryn ◽  
Françoise Van Bambeke ◽  
Marie-Paule Mingeot-Leclercq ◽  
Paul M. Tulkens
Keyword(s):  
Listeria Monocytogenes ◽  
Conventional Therapy ◽  
The Other ◽  
Intracellular Bacteria ◽  
Dependent Manner ◽  
Concentration Dependent Manner ◽  
Cellular Accumulation ◽  
Intracellular Activities ◽  
The Difference ◽  
In Cells

ABSTRACT The activities of ampicillin, meropenem, azithromycin, gentamicin, ciprofloxacin, and moxifloxacin against intracellular hemolysin-positive Listeria monocytogenes were measured in human THP-1 macrophages and were compared with the extracellular activities observed in broth. All extracellular concentrations were adjusted to explore ranges that are clinically achievable in human serum upon conventional therapy. In broth, ampicillin, meropenem, and azithromycin were only bacteriostatic, whereas gentamicin, ciprofloxacin, and moxifloxacin were strongly bactericidal in a concentration-dependent manner. In cells, ampicillin, meropenem, azithromycin, and ciprofloxacin were slightly bactericidal (0.3- to 0.8-log CFU reductions), moxifloxacin was strongly bactericidal (2.1-log CFU reduction), and gentamicin was virtually inactive. The difference in the efficacies of moxifloxacin and ciprofloxacin in cells did not result from a difference in levels of accumulation in cells (6.96 ± 1.05 versus 7.75 ± 1.03) and was only partially explainable by the difference in the MICs (0.58 ± 0.04 versus 1.40 ± 0.17 mg/liter). Further analysis showed that intracellular moxifloxacin expressed only approximately 1/7 of the activity demonstrated against extracellular bacteria and ciprofloxacin expressed only 1/15 of the activity demonstrated against extracellular bacteria. Gentamicin did not increase the intracellular activities of the other antibiotics tested. The data suggest (i) that moxifloxacin could be of potential interest for eradication of the intracellular forms of L. monocytogenes, (ii) that the cellular accumulation of an antibiotic is not the only determinant of its intracellular activity (for fluoroquinolones, it is actually a self-defeating process as far as activity is concerned), and (iii) that pharmacodynamics (activity-to-concentration relationships) need to be considered for the establishment of efficacy against intracellular bacteria, just as they are for the establishment of efficacy against extracellular infections.

scholarly journals Low-temperature Germination of Melons Is Affected by Seedcoat Characteristics and Embryo Genotype

HortScience ◽  
2009 ◽  
Vol 44 (5) ◽  
pp. 1412-1414 ◽  
Author(s):  
Menahem Edelstein ◽  
Haim Nerson
Keyword(s):  
Low Temperature ◽  
Germination Rate ◽  
Germination Percentage ◽  
The Other ◽  
Pressure Force ◽  
Cold Tolerant ◽  
Cold Sensitive ◽  
The Difference ◽  
Melon Seeds ◽  
Dominant Genes

Germination percentage and germination rate were examined in two melon accessions differing in their ability to germinate under low temperature and in their reciprocal F1, F2, and BC1 progeny. The seedcoat structure, pressure force required for seedcoat splitting, and the response to hilum sealing of the reciprocal F1s were examined as well. The purpose of this study was to elucidate the effects of embryonic genotype and seedcoat characteristics on the ability of melon seeds to germinate under low temperature. The results of the study point out that both components are strongly involved in low-temperature germination. The cold tolerant parent, ‘Persia 202’ (P202), germinated greater than 90% at 15 °C, whereas the cold-sensitive parent, ‘Noy Yizre'el’ (NY), did not germinate at all. The P202 × NY F1 and the reciprocal F2 germinated 80% to 90%, whereas the NY × P202 F1 germination percentage was only 71%. Backcrosses of the reciprocal F1 to the parents revealed that if the cross was to the tolerant one, the seeds germinated greater than 90%, but if the F1s were backcrossed to the sensitive parent, the seeds had only 56% to 60% germination. Data collected suggest that several dominant genes are carried by P202 for low-temperature germination. On the other hand, the difference in germination percentages between the reciprocal F1 demonstrates that the different seedcoats also play a role.

scholarly journals Antimicrobial activity of autoclaved and non autoclaved copaiba oil on Listeria monocytogenes

2010 ◽  
Vol 40 (8) ◽  
pp. 1797-1801 ◽  
Author(s):  
Fábio Alessandro Pieri ◽  
Raphaela Mansur José ◽  
Newton Nascentes Galvão ◽  
Luis Augusto Nero ◽  
Maria Aparecida Scatamburlo Moreira
Keyword(s):  
Listeria Monocytogenes ◽  
Antimicrobial Effect ◽  
Negative Control ◽  
Food Preservation ◽  
The Other ◽  
Diffusion Test ◽  
Food Borne ◽  
Agar Diffusion Test ◽  
Copaiba Oil ◽  
Bacteria Inhibition

The aim of this study was to evaluate the antimicrobial effect of different copaiba oil concentrations against the growth of Listeria monocytogenes, and analyze differences in inhibition of microorganisms with autoclaved and non autoclaved oil. This study provided an agar diffusion test with six isolates of bacteria and six different concentrations of autoclaved or non autoclaved copaiba oil and a negative control. The results showed sensitivity of five L. monocytogenes isolates related to the 10% autoclaved solution of copaiba oil. Four strains also showed sensitivity to the 5% autoclaved solution and one to 2.5% autoclaved solution. The 10% non autoclaved oil solution showed growth inhibition only for two strains. These results had pointed the 10% autoclaved solution of copaiba oil with higher inhibition as all other solutions and concentrations tested (P<0.05). For the other concentrations of both solutions, the 5 and 2.5% autoclaved and 10% non autoclaved solutions had presented statistically equal. All other concentrations of both copaiba solutions and the negative control did not presented any bacteria inhibition. In conclusion, the results of this study suggest that the autoclaved copaiba oil may be a potential new agent source for infection control or for food preservation, inhibiting the growth of food-borne bacteria such as L. monocytogenes.

scholarly journals Validation of an ampicillin selection protocol to enrich for mutants of Listeria monocytogenes unable to replicate on fresh produce

2019 ◽  
Vol 366 (7) ◽  
Author(s):  
Victor Jayeola ◽  
C Parsons ◽  
L Gorski ◽  
S Kathariou
Keyword(s):  
Listeria Monocytogenes ◽  
Genetic Factors ◽  
Fresh Produce ◽  
Mixed Cultures ◽  
Bacterial Cells ◽  
Sensitive Mutant ◽  
Relative Recovery ◽  
Cold Sensitive ◽  
Selection Protocol

ABSTRACT Several outbreaks of listeriosis have implicated fresh produce but genetic factors required for growth of Listeria monocytogenes on produce remain poorly characterized. Based on the fact that β-lactam antibiotics only kill bacterial cells that are growing, we hypothesized that ampicillin selection can enrich for L. monocytogenes mutants unable to grow on produce. For validation, we examined relative recovery of L. monocytogenes strain 2011L-2858 and its cold-sensitive mutant L1E4 following inoculation of cantaloupe rind fragments with 1:1 mixture of the strains and incubation at 4°C with or without ampicillin. Listeria monocytogenes from rind fragments inoculated with the mixed cultures and incubated in the presence of ampicillin were used to inoculate fresh rind fragments for a second round of enrichment. In the presence of ampicillin, the proportion of L1E4 increased from 55% on day 0 to 78% on day 14, with higher recovery (85% after 14 days) in the second round of enrichment. These data suggested that L1E4 was enriched on cantaloupe rind fragments while growing cells of the wildtype were killed by ampicillin. Application of this protocol to transposon mutant libraries from three L. monocytogenes strains yielded several mutants unable to grow on cantaloupe. Thus, ampicillin selection can facilitate discovery of genes essential for growth of L. monocytogenes on fresh produce.

Characteristics of the autolysis of variants ofLactococcus lactissubsp.cremoris

1989 ◽  
Vol 56 (4) ◽  
pp. 639-649 ◽  
Author(s):  
Kaarina Niskasaari
Keyword(s):  
Cell Wall ◽  
Sodium Dodecyl ◽  
Lipoteichoic Acid ◽  
Hydrolytic Activity ◽  
Exponential Phase ◽  
The Other ◽  
Intact Cells ◽  
Whole Cells ◽  
Autolytic Activity ◽  
The Difference

SummaryTwo slime-forming strains (T5and MLS96) and a non-slime-forming strain (HA)of Lactococcus lactissubsp.cremoriswere investigated for autolysis and optimal conditions for the autolytic process were developed. The rate of autolysis was maximal in exponential phase cells in 0·01 M-Na phosphate buffer, pH 6·5–7·5, at 30–45 °C. Autolysis of the native exponential phase walls was activated by trypsin and inhibited by lipoteichoic acid and cardiolipin. Decreased trypsin activation was found in intact exponential phase cells and no activation in stationary phase cells.N-acetylmuramylhydrolase action in the autolytic system ofLc. lactissubsp.cremorisstrains was indicated by the progressive release of reducing groups. No amidase or endopeptidase action was found. Great variation in the rate of autolysis of whole cells was observed between the two slime-forming strains. Intact cells of strain T5exhibited decreased autolytic activity, but a higher rate of autolysis of isolated exponential phase walls. Autolysins from strain T5walls exhibited lower hydrolytic activity against sodium dodecyl sulphate-treated walls of the other two strains as compared with strains MLS96 and HA. Quantitative analysis revealed higher protein and phosphorus and lower hexosamine and rhamnose in cell wall preparations of strain T5compared with the other two strains. Results suggest that the decreased rate of autolysis of strain T5cells may at least in part be caused by cell surface components other than cell-wall peptidoglycan. It is proposed that the difference in autolytic characteristics should be used as a criterion when selecting starter strains of lactococci (streptococci).

scholarly journals Growth and membrane fluidity of food-borne pathogen Listeria monocytogenes in the presence of weak acid preservatives and hydrochloric acid

2013 ◽  
Vol 4 ◽  
Author(s):  
Ioannis Diakogiannis ◽  
Anita Berberi ◽  
Eleni Siapi ◽  
Angeliki Arkoudi-Vafea ◽  
Lydia Giannopoulou ◽  
...  
Keyword(s):  
Listeria Monocytogenes ◽  
Hydrochloric Acid ◽  
Membrane Fluidity ◽  
Weak Acid ◽  
Food Borne

Enhancement of ADP-induced Platelet Aggregation by Adrenaline in Vivo and Its Prevention

1973 ◽  
Vol 29 (02) ◽  
pp. 490-498 ◽  
Author(s):  
Hiroh Yamazaki ◽  
Itsuro Kobayashi ◽  
Tadahiro Sano ◽  
Takio Shimamoto
Keyword(s):  
Platelet Count ◽  
Platelet Aggregation ◽  
Platelet Rich Plasma ◽  
The Other ◽  
Endothelial Surface ◽  
Important Interaction ◽  
Blood Coagulability ◽  
The Difference

SummaryThe authors previously reported a transient decrease in adhesive platelet count and an enhancement of blood coagulability after administration of a small amount of adrenaline (0.1-1 µg per Kg, i. v.) in man and rabbit. In such circumstances, the sensitivity of platelets to aggregation induced by ADP was studied by an optical density method. Five minutes after i. v. injection of 1 µg per Kg of adrenaline in 10 rabbits, intensity of platelet aggregation increased to 115.1 ± 4.9% (mean ± S. E.) by 10∼5 molar, 121.8 ± 7.8% by 3 × 10-6 molar and 129.4 ± 12.8% of the value before the injection by 10”6 molar ADP. The difference was statistically significant (P<0.01-0.05). The above change was not observed in each group of rabbits injected with saline, 1 µg per Kg of 1-noradrenaline or 0.1 and 10 µg per Kg of adrenaline. Also, it was prevented by oral administration of 10 mg per Kg of phenoxybenzamine or propranolol or aspirin or pyridinolcarbamate 3 hours before the challenge. On the other hand, the enhancement of ADP-induced platelet aggregation was not observed in vitro, when 10-5 or 3 × 10-6 molar and 129.4 ± 12.8% of the value before 10∼6 molar ADP was added to citrated platelet rich plasma (CPRP) of rabbit after incubation at 37°C for 30 second with 0.01, 0.1, 1, 10 or 100 µg per ml of adrenaline or noradrenaline. These results suggest an important interaction between endothelial surface and platelets in connection with the enhancement of ADP-induced platelet aggregation by adrenaline in vivo.

Energy Approximation

2017 ◽  
Author(s):  
Philip Isett
Keyword(s):  
Main Lemma ◽  
The Other ◽  
Coarse Scale ◽  
Continuous Solutions ◽  
Material Derivative ◽  
Energy Variation ◽  
Energy Approximation ◽  
The Difference ◽  
Derivatives Of

This chapter presents the equations and calculations for energy approximation. It establishes the estimates (261) and (262) of the Main Lemma (10.1) for continuous solutions; these estimates state that we are able to accurately prescribe the energy that the correction adds to the solution, as well as bound the difference between the time derivatives of these two quantities. The chapter also introduces the proposition for prescribing energy, followed by the relevant computations. Each integral contributing to the other term can be estimated. Another proposition for estimating control over the rate of energy variation is given. Finally, the coarse scale material derivative is considered.

Pengaruh Unsur Budaya Lokal dalam Ungkapan Berbahasa Perancis

Metahumaniora ◽  
2017 ◽  
Vol 7 (3) ◽  
pp. 378
Author(s):  
Vincentia Tri Handayani
Keyword(s):  
Mental Representation ◽  
Cultural Context ◽  
Oral Tradition ◽  
Minimal Element ◽  
The Other ◽  
Local Culture ◽  
Community Groups ◽  
Cultural Community ◽  
The Difference ◽  
Complex Words

AbstrakFolklor yang menghasilkan tradisi lisan merupakan perwujudan budaya yang lahirdari pengalaman kelompok masyarakat. Salah satu bentuk tradisi lisan adalah ungkapan yangmengandung unsur budaya lokal dalam konstruksinya yang tidak dimiliki budaya lainnya.Ungkapan idiomatis memberikan warna pada bahasa melalui penggambaran mental. Dalambahasa Perancis, ungkapan dapat berupa locution dan expression. Perbedaan motif acuansuatu ungkapan dapat terlihat dari pengaruh budaya masyarakat pengguna bahasa. Sebuahleksem tidak selalu didefinisikan melalui unsur minimal, tidak juga melalui kata-kata,baik kata dasar atau kata kompleks, namun dapat melalui kata-kata beku yang maknanyatetap. Hubungan analogis dari makna tambahan yang ada pada suatu leksem muncul dariidentifikasi semem yang sama. Semem tersebut mengarah pada term yang diasosiasikan danyang diperkaya melalui konteks (dalam ungkapan berhubungan dengan konteks budaya).Kata kunci: folklor, ungkapan, struktur, makna idiomatis, kebudayaanAbstractFolklore which produces the oral tradition is a cultural manifestation born out theexperience of community groups. One form of the oral tradition is a phrase that containsthe elements of local culture in its construction that is not owned the other culture. Theidiomatic phrase gives the color to the language through the mental representation. InFrench, the expression can consist of locution and expression. The difference motivesreference of an expression can be seen from the influence of the cultural community thelanguage users. A lexeme is not always defined through a minimal element, nor throughwords, either basic or complex words, but can be through the frost words whose meaningsare fixed. The analogical connection of the additional meanings is on a lexeme arises fromthe identification of the same meaning. The meaning ‘semem’ leads to the associated termsand which are enriched through the context (in idiom related to the cultural context).Keywords : folklore, idioms, structure, idiom meaning, cultureI PENDAHULUAN

Biofilm Formation and Associated Genes in Listeria Monocytogenes

2017 ◽  
Vol 12 (3) ◽  
Author(s):  
S. R. Warke ◽  
V. C. Ingle ◽  
N. V. Kurkure ◽  
P. A. Tembhurne ◽  
Minakshi Prasad ◽  
...  
Keyword(s):  
Public Health ◽  
Listeria Monocytogenes ◽  
Multiplex Pcr ◽  
Food Processing ◽  
Biofilm Formation ◽  
Milk Samples ◽  
Biofilm Production ◽  
Food Borne ◽  
Serious Infections ◽  
Microtiter Assay

Listeria monocytogenes, an opportunistic food borne pathogen can cause serious infections in immunocompromised individuals. L. monocytogenes is capable of producing biofilm on the surface of food processing lines and instruments.The biofilm transfers contamination to food products and impose risk to public health. In the present study biofilm producing ability of L. monocytogenes isolates were investigated phenotypically and genotypically by microtiter assay and multiplex PCR, respectively. Out of 38 L. monocytogenes isolates 14 were recovered from animal clinical cases, 12 bovine environment and 12 from milk samples. A total of 3 (21.42%) clinical, 2 (16.66%) environment and 3 (25%) milk samples respectively, revealed biofilm production in microtiter assay. Cumulative results showed that 23 (60.52%) out of 38 strains of L. monocytogenes were positive for luxS and flaA gene and 1 (2.63%) was positive only for the flaA gene.

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