Inactivation of a Cold-Induced Putative RNA Helicase Gene of Listeria monocytogenes Is Accompanied by Failure To Grow at Low Temperatures but Does Not Affect Freeze-Thaw Tolerance

2010 ◽  
Vol 73 (8) ◽  
pp. 1474-1479 ◽  
Author(s):  
REHA O. AZIZOGLU ◽  
S. KATHARIOU
Keyword(s):  
Listeria Monocytogenes ◽  
Normal Growth ◽  
Rna Helicase ◽  
Soft Agar ◽  
Freezing And Thawing ◽  
Freeze Thaw ◽  
Transposon Insertion ◽  
Helicase Gene ◽  
Repeated Freezing ◽  
Cold Sensitive

Freeze-thaw tolerance (cryotolerance) of Listeria monocytogenes is markedly influenced by temperature of growth of the bacteria, and may involve responses to low-temperature stresses encountered during freezing and thawing. A cold-sensitive mariner-based transposon mutant of L. monocytogenes F2365 was found to harbor a single insertion in LMOf2365_1746, encoding a putative RNA helicase, and earlier shown by other investigators to be induced during 4°C growth of L. monocytogenes. The mutant had normal growth at 37°C but completely failed to grow at either 4 or 10°C, and had impaired growth and reduced swarming on soft agar at 25°C. However, the mutation had no discernible influence on the ability of the bacteria to tolerate repeated freezing and thawing after growth at either 25 or 37°C. The findings suggest that the transposon insertion in the putative helicase gene, in spite of the severely cold-sensitive phenotype that accompanies it, does not affect the ability of the bacteria to cope with cold-related stresses encountered during repeated freezing and thawing.

FREEZE-THAW EFFECTS ON GRANULAR STRUCTURE REORGANIZATION FOR SOIL MATERIALS OF VARYING TEXTURE AND MOISTURE CONTENT

1988 ◽  
Vol 68 (3) ◽  
pp. 485-494 ◽  
Author(s):  
S. PAWLUK
Keyword(s):  
Moisture Content ◽  
Lacustrine Sediments ◽  
Field Capacity ◽  
Granular Structure ◽  
Glacial Till ◽  
Microstructural Development ◽  
Clay Loam ◽  
Freezing And Thawing ◽  
Freeze Thaw ◽  
Repeated Freezing

Repeated freezing and thawing of glacial till cores of clay loam texture results in the formation of granic and metafragmic microfabrics. These units of fabric are best developed near the surface of cores kept at moisture levels between field capacity and saturation. Well-sorted lacustrine sediments with fewer voids tend to form banded fabrics. Many of the morphological features such as vesicles, metavughs and desiccation cracks commonly attributed to freeze-thaw processes are evident in all materials tested. Discrete units of fabric observed in this study are very similar to units of fabric observed in the Ah horizons of Black Chernozemic and Cryosolic soils. Results of this investigation strongly support earlier research which suggests that frost processes are major contributors to their microstructural development. Key words: Granic, freeze-thaw, microfabrics

A Novel Method for the Reduction of Numbers of Listeria monocytogenes Cells by Freezing in Combination with an Essential Oil in Bacteriological Media

2003 ◽  
Vol 66 (3) ◽  
pp. 390-395 ◽  
Author(s):  
HAYDEN K. CRESSY ◽  
ALISTAIR R. JERRETT ◽  
CAROLYN M. OSBORNE ◽  
PHIL J. BREMER
Keyword(s):  
Listeria Monocytogenes ◽  
Most Probable Number ◽  
Polysorbate 80 ◽  
Bactericidal Action ◽  
Freezing And Thawing ◽  
Probable Number ◽  
Freeze Thaw ◽  
Cell Numbers ◽  
Low Concentrations ◽  
Novel Method

The use of multiple freeze (−20°C)–thaw cycles in combination with isoeugenol and polysorbate 80 was investigated as a method for the reduction of numbers of Listeria monocytogenes cells in a bacteriological medium. Three freeze (1 h, −20°C)–thaw cycles in the presence of isoeugenol at concentrations of 0, 100, and 300 ppm resulted in average L. monocytogenes reductions of 0.69, 2.65, and 3.3 log10 MPN (most probable number) per ml, respectively. Increasing the number of freeze–thaw cycles further decreased cell numbers, with reductions of nearly 5 log10 MPN/ml being obtained with six freeze-thaw cycles. Freeze–thaw cycles were effective in reducing cell numbers at isoeugenol concentrations down to 25 ppm. Rapid freezing rates with liquid nitrogen were found to be less effective in reducing numbers of L. monocytogenes cells. Two rapid freeze–thaw cycles in the presence of 100 ppm isoeugenol and polysorbate 80 resulted in a reduction of 1.45 log10 MPN/ml. Two freezing (−20°C) cycles involving slow freezing and thawing rates with samples being held frozen for 6 h for each cycle resulted in reductions larger than those obtained with faster freezing rates. It was found that complete thawing in freeze-thaw cycles was not necessary to achieve bactericidal action. The application of multiple freeze-thaw cycles in combination with low concentrations of isoeugenol could effectively reduce numbers of L. monocytogenes cells in bacteriological media.

Freeze/thaw stability of transferrin, and reference values obtained with kinetic nephelometry.

1984 ◽  
Vol 30 (1) ◽  
pp. 114-115 ◽  
Author(s):  
L Stoddard ◽  
W Dennis ◽  
R M Parvin ◽  
O W van Assendelft
Keyword(s):  
Reference Values ◽  
Freezing And Thawing ◽  
Freeze Thaw ◽  
Normal Reference ◽  
Repeated Freezing ◽  
Blood Specimens ◽  
Normal Adults

Abstract To determine whether transferrin is stable to repeated freezing and thawing, we used blood specimens from 100 normal adults. Their transferrin concentrations were determined by a laser kinetic nephelometric immunoassay. The sera were stored at 4 degrees C and analyzed the next day (day 1). Specimens 1-25 were stored at -20 degrees C and assayed again on days 3, 4, 8, 16, 22, and 43. Specimens 26-100 were stored at 4 degrees C and analyzed again on day 2. Transferrin proved to be stable to repeated freezing and thawing. Normal reference values with respect to sex and age are given, as determined with the Baker 420 Immunological Nephelometer.

scholarly journals Glacial and Periglacial Transformation of Palaeokarst in the Lublin-Volhynia Region (Se Poland, NW Ukraine) on the Base of TL Dating

2007 ◽  
Vol 27 (-1) ◽  
pp. 41-46 ◽  
Author(s):  
Radosław Dobrowolski ◽  
Stanisław Fedorowicz
Keyword(s):  
Genetic Relationship ◽  
Experimental Investigations ◽  
Considerable Influence ◽  
Freezing And Thawing ◽  
Tl Dating ◽  
Freeze Thaw ◽  
Se Poland ◽  
Repeated Freezing ◽  
Formation Conditions ◽  
Close Genetic Relationship

Glacial and Periglacial Transformation of Palaeokarst in the Lublin-Volhynia Region (Se Poland, NW Ukraine) on the Base of TL Dating Distinctly diverse results of TL dating are obtained for the deposits with similar lithofacial features but filling morphologically differentiated karst palaeoforms (dolines, pipes, pockets). The infillings of dolines and pipes are mostly of the Saalian age. Based on sedimentological analysis, their formation conditions are related to sub- or/and terminoglacial environment. The age obtained for all infillings of pockets is underestimated in comparison with lithostratigraphic data. A close genetic relationship between these forms and periglacial conditions seems to indicate that the reduction of TL signal is mostly influenced by the disintegration of grains resulted from the repeated freezing and thawing of glaciogenic deposits. A considerable influence of frost weathering on the decrease of thermoluminescence intensity of mineral grains is indirectly confirmed by the results of experimental investigations consisting in the repeated TL measurements of pockets' infillings after successive freeze-thaw cycles.

scholarly journals RNA Helicase Mediates Competitive Fitness of Listeria monocytogenes on the Surface of Cantaloupe

Horticulturae ◽  
2018 ◽  
Vol 4 (4) ◽  
pp. 40 ◽  
Author(s):  
Robert Price ◽  
Cameron Parsons ◽  
Sophia Kathariou
Keyword(s):  
Listeria Monocytogenes ◽  
Foodborne Pathogen ◽  
Rna Helicase ◽  
Relative Fitness ◽  
Competitive Fitness ◽  
Growth And Survival ◽  
Dead Box ◽  
Helicase Gene ◽  
Genetic Features ◽  
Flagellum Biosynthesis

Listeria monocytogenes is a foodborne pathogen that is implicated in numerous outbreaks of disease (listeriosis) via fresh produce. The genetic features of L. monocytogenes that allow adherence and growth on produce remain largely uncharacterized. In this study, two non-motile transposon mutants were characterized for attachment, growth, and survival on the surface of cantaloupe rind. One of the mutants, L1E4, harbored a single transposon insertion in a DEAD-box RNA helicase gene (lmo0866 homolog), while the other, M1A5, harbored an insertion in a gene from a flagellum biosynthesis and chemotaxis gene cluster (lmo0694 homolog). When inoculated alone, neither mutant was significantly impaired in growth or survival on the surface of cantaloupe at either 25 or 37 °C. However, when co-inoculated with the wildtype parental strain, the RNA helicase mutant L1E4 had a clear competitive disadvantage, while the relative fitness of M1A5 was not noticeably impacted. Genetic complementation of L1E4 with the intact RNA helicase gene restored relative fitness on cantaloupe. The findings suggest that the DEAD-box RNA helicase encoded by the lmo0866 homolog is critical for relative fitness of L. monocytogenes on cantaloupe. Mutant L1E4 was pleiotropic, being not only non-motile but also cold-sensitive and with reduced hemolytic activity, warranting further studies to elucidate the role of this helicase in the competitive fitness of L. monocytogenes on produce.

scholarly journals PSIV-25 Effect of Various Handling Methods of Plasma and Serum Samples on Pregnancy Associated Glycoprotein Concentrations

2020 ◽  
Vol 98 (Supplement_4) ◽  
pp. 289-290
Author(s):  
Grace M Wesson ◽  
Lohana Fernandez ◽  
Rebecca K Poole ◽  
Gessica A Franco ◽  
Sydney T Reese ◽  
...  
Keyword(s):  
Monoclonal Antibodies ◽  
Plasma Samples ◽  
Freezing And Thawing ◽  
Serum Samples ◽  
Freeze Thaw ◽  
Thaw Cycle ◽  
Freeze Thaw Cycle ◽  
Repeated Freezing ◽  
Pregnancy Status ◽  
Handling Methods

Abstract Pregnancy associated glycoproteins (PAG) can be used as a biomarker for early pregnancy diagnosis, so accurate and consistent PAG detection is critical. The objective of this study was to determine if plasma and serum PAG concentrations were altered when centrifugation occurred at different times post-collection, when subjected to repeated freezing and thawing, and when monoclonal antibodies were kept in frequently or infrequently opened containers. Plasma (n = 4) and serum (n = 4) samples were collected from two open cows and two pregnant cows 28 days after artificial insemination. Pregnancy status was determined via transrectal ultrasonography. Plasma and serum samples were evenly separated and either centrifuged on the day of collection, or placed at 4°C and centrifuged the next day. An in-house PAG ELISA was performed on all samples before freezing (NOTHAW), after being frozen for one week (INTACT), after one freeze/thaw cycle (THAW1), two freeze/thaw cycles (THAW2), and three freeze/thaw cycles (THAW3). Data were analyzed using one-way ANOVA (GLM procedure, SAS 9.4). All samples from open cows were below the baseline of the assay. For pregnant cows, plasma samples had greater PAG concentrations than serum samples (11.84 vs 3.30 ± 0.66 ng/mL, respectively, P < 0.05). No differences were observed for day of centrifugation in both plasma and serum samples (P = 0.50 and P = 0.60, respectively) and in handling of monoclonal antibodies (P = 0.90). Freezing and thawing did not impact PAG concentrations in plasma samples (P = 0.19), but did alter serum concentrations (P = 0.01). Specifically, THAW1 (1.98 ng/mL) and THAW2 (1.42 ng/mL) serum PAG concentrations were lower compared to NOTHAW, THAW3, and INTACT samples (4.66, 4.85, and 3.57 ng/mL, respectively). Based on these data, plasma yields more consistent results than serum, even after several freeze-thaw cycles, and handling of monoclonal antibodies or time of centrifugation has no significant effect on measured PAG.

scholarly journals Freeze-Thaw Splitting Strength Analysis of PAC Based on the Gray-Markov Model

2021 ◽  
Vol 2021 ◽  
pp. 1-12
Author(s):  
Baoyang Yu ◽  
Zongguang Sun ◽  
Lin Qi
Keyword(s):  
Markov Model ◽  
Strength Analysis ◽  
Rapid Decline ◽  
Water Stability ◽  
Freezing And Thawing ◽  
Sem Images ◽  
Freeze Thaw ◽  
Split Ratio ◽  
Repeated Freezing ◽  
Markov Method

In this study, a freeze-thaw split test was carried out to simulate the frost-heaving behavior of permeable asphalt concrete (PAC). Furthermore, the water stability problems caused by spalling and loosening were studied. Through a comparative analysis of the freeze-thaw split ratio of porosities of 19%, 21%, and 24%, the PAC porosity with excellent water stability was determined to be 19–21%. Scanning electron microscopy (SEM) images of PAC with the three porosity values after repeated freezing and thawing verified that the porosities were greater than 24% and the asphalt film peeling area was the largest, resulting in the rapid decline of the PAC freeze-thaw split ratio. The Gray-Markov model was used to predict the water stability of the mixture with a porosity of 21%. Based on the results, a Gray-Markov method for evaluating the PAC water stability in seasonally frozen areas was introduced.

scholarly journals Experimental Investigation of the Variation of Concrete Pores under the Action of Freeze-Thaw Cycles by Using X-Ray CT

2014 ◽  
Vol 2014 ◽  
pp. 1-11 ◽  
Author(s):  
Jie Yuan ◽  
Yang Liu ◽  
Hongxia Li ◽  
Baokun Zhang
Keyword(s):  
Experimental Investigation ◽  
Image Analysis ◽  
Failure Process ◽  
Statistical Characteristics ◽  
Freezing And Thawing ◽  
X Ray ◽  
Freeze Thaw ◽  
Complete Disintegration ◽  
Repeated Freezing ◽  
Extent Of Damage

The variation of concrete pores under the action of freeze-thaw cycles was investigated experimentally by using the X-ray CT. Firstly, the statistical characteristics of pores of concrete specimens were obtained by using the X-ray image analysis. Secondly, the variation of porosity and pore volume of concrete pores were analyzed and discussed by comparing with above characteristics. Thirdly, the failure process of the concrete specimens acted by the freeze-thaw cycles was investigated by scanning the interior of concrete specimens. The results showed that the pore volumes of concrete pores whose volumes were located at the interval [0.5 mm3, 20 mm3] have no big variation in both the amounts and volume of concrete pores, while others were found to have huge change during the process of experiment. The extent of damage acted by the repeated freezing and thawing gradually ranged from surface to complete disintegration of the interior of concrete specimens after 30 cycles of freeze-thaw acting.

scholarly journals Temperature-Dependent Requirement for Catalase in Aerobic Growth of Listeria monocytogenes F2365

2010 ◽  
Vol 76 (21) ◽  
pp. 6998-7003 ◽  
Author(s):  
Reha Onur Azizoglu ◽  
Sophia Kathariou
Keyword(s):  
Oxidative Stress ◽  
Listeria Monocytogenes ◽  
Stress Responses ◽  
Normal Growth ◽  
Severe Illness ◽  
Aerobic Growth ◽  
Transposon Insertion ◽  
Wide Range ◽  
The Impact ◽  
Oxidative Stress Responses

ABSTRACT Listeria monocytogenes is a Gram-positive, psychrotrophic, facultative intracellular food-borne pathogen responsible for severe illness (listeriosis). The bacteria can grow in a wide range of temperatures (1 to 45°C), and low-temperature growth contributes to the food safety hazards associated with contamination of ready-to-eat foods with this pathogen. To assess the impact of oxidative stress responses on the ability of L. monocytogenes to grow at low temperatures and to tolerate repeated freeze-thaw stress (cryotolerance), we generated and characterized a catalase-deficient mutant of L. monocytogenes F2365 harboring a mariner-based transposon insertion in the catalase gene (kat). When grown aerobically on blood-free solid medium, the kat mutant exhibited impaired growth, with the extent of impairment increasing with decreasing temperature, and no growth was detected at 4°C. Aerobic growth in liquid was impaired at 4°C, especially under aeration, but not at higher temperatures (10, 25, or 37°C). Genetic complementation of the mutant with the intact kat restored normal growth, confirming that inactivation of this gene was responsible for the growth impairment. In spite of the expected impact of oxidative stress responses on cryotolerance, cryotolerance of the kat mutant was not affected.

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