• Journal of Microbiology and Biotechnology
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• v.29 no.12
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• pp.1916-1924
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• 2019

Outbreaks of staphylococcal food poisoning (SFP) causing serious human diseases and economic losses have been reported globally. Furthermore, the spread of Staphylococcus aureus with increased resistance to multiple antimicrobial agents has become a major concern in the food industries and medicine. Here, we isolated an endolysin LysSAP8, as one of the peptidoglycan hydrolases, derived from the bacteriophage SAP8 infecting S. aureus. This endolysin was tagged with a 6×His at the C-terminal of the target protein and purified using affinity chromatography. LysSAP8 demonstrated lytic activity against a broad spectrum of bacteria, which included a majority of the staphylococcal strains tested in this study as well as the methicillin-resistant S. aureus (MRSA); however, no such activity was observed against other gram-positive or gram-negative bacteria. Additionally, LysSAP8 could maintain bactericidal activity until 0.1 nM working concentration and after heat treatment at 37℃ for 30 min. The ability of LysSAP8 to lyse cells under varying conditions of temperature (4-43℃), pH (3-9), and NaCl concentrations (0-1,000 mM), and divalent metal ions (Ca²⁺, Co²⁺, Cu²⁺, Mg²⁺, Mn²⁺, Hg²⁺, and Zn²⁺) was examined. At the optimized condition, LysSAP8 could disrupt approximately 3.46 log CFU/ml of the planktonic cells in their exponential phase of growth within 30 min. In this study, we have suggested that LysSAP8 could be a potent alternative as a biocontrol agent that can be used to combat MRSA.

• Computers and Concrete
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• v.19 no.1
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• pp.59-68
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• 2017

This study focused on modeling the behavior of the compressive stress using the average strain and ultrasonic test results in concrete. Feed-forward backpropagation artificial neural network (ANN) models were used to compare four types of concrete mixtures with varying water cement ratio (WC), ordinary concrete (ORC) and concrete with short steel fiber-reinforcement (FRC). Sixteen (16) $150mm{\times}150mm{\times}150mm$ concrete cubes were used; each contained eighteen (18) data sets. Ultrasonic test with pitch-catch configuration was conducted at each loading state to record linear and nonlinear test response with multiple step loads. Statistical Spearman's rank correlation was used to reduce the input parameters. Different types of concrete produced similar top five input parameters that had high correlation to compressive stress: average strain (${\varepsilon}$), fundamental harmonic amplitude (A1), $2^{nd}$ harmonic amplitude (A2), $3^{rd}$ harmonic amplitude (A3), and peak to peak amplitude (PPA). Twenty-eight ANN models were trained, validated and tested. A model was chosen for each WC with the highest Pearson correlation coefficient (R) in testing, and the soundness of the behavior for the input parameters in relation to the compressive stress. The ANN model showed increasing WC produced delayed response to stress at initial stages, abruptly responding after 40%. This was due to the presence of more voids for high water cement ratio that activated Contact Acoustic Nonlinearity (CAN) at the latter stage of the loading path. FRC showed slow response to stress than ORC, indicating the resistance of short steel fiber that delayed stress increase against the loading path.

• Steel and Composite Structures
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• v.17 no.4
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• pp.471-495
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• 2014

The responses of steel buildings with perimeter moment resisting frames (PMRF) with medium size columns (W14) are estimated and compared with those of buildings with deep columns (W27), which are selected according to two criteria: equivalent resistance and equivalent weight. It is shown that buildings with W27 columns have no problems of lateral torsional, local or shear buckling in panel zone. Whether the response is larger for W14 or W27 columns, depends on the level of deformation, the response parameter and the structural modeling under consideration. Modeling buildings as two-dimensional structures result in an overestimation of the response. For multiple response parameters, the W14 columns produce larger responses for elastic behavior. The axial load on columns may be significantly larger for the buildings with W14 columns. The interstory displacements are always larger for W14 columns, particularly for equivalent weight and plane models, implying that using deep columns helps to reduce interstory displacements. This is particularly important for tall buildings where the design is usually controlled by the drift limit state. The interstory shears in interior gravity frames (GF) are significantly reduced when deep columns are used. This helps to counteract the no conservative effect that results in design practice, when lateral seismic loads are not considered in GF of steel buildings with PMRF. Thus, the behavior of steel buildings with deep columns, in general, may be superior to that of buildings with medium columns, using less weight and representing, therefore, a lower cost.

• Asian-Australasian Journal of Animal Sciences
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• v.18 no.9
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• pp.1336-1342
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• 2005

The present research work was conducted to evaluate the beneficial effects as well as the safety aspects of lactobacilli as probiotic. Lactobacilli were isolated from poultry faecal samples, feed samples and from some known preparations procured from poultry feed manufacturers. L. acidophilus and L. sporogenes were tested for the antibacterial activity against four poultry pathogens viz. Escherichia coli, Salmonella spp., Proteus spp. and Pseudomonas aeruginosa. Cell free supernatant (CFS) of L. acidophilus exhibited significantly higher antibacterial activity against Salmonella spp. at original pH (4.50${\pm}$0.02). At the adjusted pH (6.50${\pm}$0.02) significantly higher antibacterial activity was recorded against indicator organism except for P. aeruginosa. Likewise, L. sporogenes exhibited similar antibacterial activity at original as well as adjusted pH except for E. coli. Antibacterial activity against E. coli was significantly higher at adjusted pH than at original pH of CFS. The competitive exclusion of E. coli by lactobacilli over the intestinal epithelial cells (IEC) was checked. L. acidophilus strain I, which was of poultry origin, exhibited maximum attachment over IEC as compared to other three strains of non-poultry origin viz. L. acidophilus strain II, L. sporogenes strain I and II. Overall, L. acidophilus exhibited higher competitive exclusion as compared to L. sporogenes. All the lactobacilli of poultry origin were most sensitive to penicillin G, amoxycillin, ampicillin and chloramphenicol, least sensitive to sulphamethizole, ciprofloxacin, neomycin, norfloxacin and pefloxacin and resistant to metronidazole and nalidixic acid. The isolates from probiotic preparations were most sensitive to ampicillin, amoxycillin and tetracycline, least sensitive to sulphamethizole, norfloxacin, neomycin and ceftriazone and resistant to nalidixic acid and metronidazole. Eight of the multiple drug resistant lactobacilli isolates were studied for the presence of plasmids. Plasmids could be extracted from six isolates of lactobacilli. These plasmids could be responsible for bacteriocin production or for antibiotic resistance of the strains. The lactobacilli need further studies regarding their safety for use in the probiotic preparations.

• Journal of Microbiology and Biotechnology
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• v.30 no.7
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• pp.982-995
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• 2020

A putative multidrug efflux gene, yddA, was cloned from the Escherichia coli K-12 strain. A drug-sensitive strain of E. coli missing the main multidrug efflux pump AcrB was constructed as a host and the yddA gene was knocked out in wild-type (WT) and drug-sensitive E. coliΔacrB to study the yddA function. Sensitivity to different substrates of WT E.coli, E. coliΔyddA, E. coliΔacrB and E. coliΔacrBΔyddA strains was compared with minimal inhibitory concentration (MIC) assays and fluorescence tests. MIC assay and fluorescence test results showed that YddA protein was a multidrug efflux pump that exported multiple substrates. Three inhibitors, ortho-vanadate, carbonyl cyanide m-chlorophenylhydrazone (CCCP), and reserpine, were used in fluorescence tests. Ortho-vanadate and reserpine significantly inhibited the efflux and increased accumulation of ethidium bromide and norfloxacin, while CCCP had no significant effect on YddA-regulated efflux. The results indicated that YddA relies on energy released from ATP hydrolysis to transfer the substrates and YddA is an ABC-type multidrug exporter. Functional study of unknown ATP-binding cassette (ABC) superfamily transporters in the model organism E. coli is conducive to discovering new multidrug resistance-reversal targets and providing references for studying other ABC proteins of unknown function.

• Journal of Microbiology and Biotechnology
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• v.22 no.11
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• pp.1557-1567
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• 2012

Glutathione reductase (GR, E.C. 1.6.4.2) is an important enzyme that reduces glutathione disulfide (GSSG) to a sulfydryl form (GSH) in the presence of an NADPH-dependent system. This is a critical antioxidant mechanism. Owing to the significance of GR, this enzyme has been examined in a number of animals, plants, and microbes. We performed a study to evaluate the molecular properties of GR (OsGR) from rice (Oryza sativa). To determine whether heterologous expression of OsGR can reduce the deleterious effects of unfavorable abiotic conditions, we constructed a transgenic Saccharomyces cerevisiae strain expressing the GR gene cloned into the yeast expression vector p426GPD. OsGR expression was confirmed by a semiquantitative reverse transcriptase polymerase chain reaction (semiquantitative RT-PCR) assay, Western-blotting, and a test for enzyme activity. OsGR expression increased the ability of the yeast cells to adapt and recover from $H_2O_2$-induced oxidative stress and various stimuli including heat shock and exposure to menadione, heavy metals (iron, zinc, copper, and cadmium), sodium dodecyl sulfate (SDS), ethanol, and sulfuric acid. However, augmented OsGR expression did not affect the yeast fermentation capacity owing to reduction of OsGR by multiple factors produced during the fermentation process. These results suggest that ectopic OsGR expression conferred acquired tolerance by improving cellular homeostasis and resistance against different stresses in the genetically modified yeast strain, but did not affect fermentation ability.

• Journal of Microbiology and Biotechnology
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• v.23 no.11
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• pp.1560-1568
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• 2013

Salmonella, a main cause of foodborne diseases, encounters a variety of environmental stresses and overcomes the stresses by multiple resistance strategies. One of the general responses to hyperosmotic stress is to import or produce compatible solutes so that cells maintain fluid balance and protect proteins and lipids from denaturation. The ProP and ProU systems are the main transport systems for compatible solutes. The OsmU system, recently identified as a third osmoprotectant transport system, debilitates excessive growth as well by reducing production of trehalose. We studied a fourth putative osmoprotectant transport system, YehZYXW, with high sequence similarity with the OsmU system. A Salmonella strain lacking YehZ, a predicted substrate-binding protein, did not suffer from hyperosmolarity but rather grew more rapidly than the wild type regardless of glycine betaine, an osmoprotectant, suggesting that the YehZYXW system controls bacterial growth irrespective of transporting glycine betaine. However, the growth advantage of ${\Delta}yehZ$ was not attributable to an increase in OtsBA-mediated trehalose production, which is responsible for the outcompetition of the ${\Delta}osmU$ strain. Overexpressed YehZ in trans was capable of deaccelerating bacterial growth vice versa, supporting a role of YehZ in dampening growth. The expression of yehZ was increased in response to nutrient starvation, acidic pH, and the presence of glycine betaine under hyperosmotic stress. Identifying substrates for YehZ will help decipher the role of the YehZYXW system in regulating bacterial growth in response to environmental cues.

• The Journal of the Korea Contents Association
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• v.17 no.1
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• pp.692-700
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• 2017

Based on the sexual offenses committed in school, the present study investigated differences between habitual/repeated sexual offenses and one-off sexual offenses in terms of offender characteristics, victim characteristics, and offense characteristics. We examined a total of 218 sexual offense cases committed in school. As a result, we found significant differences in the age, job, and residential area between habitual/repeated and one-off sexual offenders in school. In addition, notable differences were found between habitual/repeated and one-off sexual offense cases in the age and alcohol use of the victim. Moreover, habitual/repeated and one-off sexual offenses in school differed significantly by offense planning, method of approaching the victim, type of sexual behavior, and victim resistance. Furthermore, we conducted regression analyses and identified multiple factors that contributed to lasting of the sexual offense in school. Finally, we discussed limitations of the present study and made suggestions for future research.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.38C no.11
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• pp.955-965
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• 2013

The joint tactical information distribution system (JTIDS) is used as the communication terminal of Link-16 by the United States armed forces, north atlantic treaty organization (NATO), and other allied forces. A portion of Link-16 frequencies may be shortly remapped to other systems owing to the growing demand for frequencies, especially in civil aviation, which is witnessing a constant increase in air traffic. This will affect the performance of Link-16. Therefore, in this paper, we analyze the effect of frequency band reduction on the performance of Link-16 waveform under partial-band noise jamming with Nakagami fading, via simulation and numerical analysis. The multi-net and anti-jamming performance of Link-16 with frequency remapping is compared with that of conventional Link-16 systems. The results show that the performance of Link-16 waveform is degraded with the reduction in frequencies. Nonetheless, Link-16 retains its jam resistance, and it can support multiple users in the same time slots.

• Biomedical Science Letters
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• v.5 no.1
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• pp.27-40
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• 1999

This study was focused on the evaluation of MarB alongside with MarA for its regulatory effects upon the efflux function of AcrAB pump, which were induced or not, perhaps as a target. Transductions of marR and/or acrAB mutation which were derived from Mar and/or AcrAB mutants of wild type E. coli K-12, respectively, into the multicopy plasmid in wild type E. coli backgrounds or into the chromosome of isogenic parents were done. Minimal inhibitory concentration (MIC) of transduced mutants was compared with their original mutants. This study reports the indirect evidences that suggests a model in which MarB along with MarA have a putative negative regulatory effect upon the efflux function of AcrAB/TolC pump while MarA alone have a positive regulatory effect to the expression of acrRAB operon at transcription level. The target of MarB with MarA for its putative negative regulator might be the AcrAB efflux pump. Another efflux system (s) might be negatively regulated by MarB with MarA, and be involved in the efflux of antibiotics which were otherwise extruded preferentially by AcrAB efflux pump.