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Bai, Jaewoo,Jeon, Byeonghwa,Ryu, Sangryeol Elsevier 2019 Food microbiology Vol.77 No.-
<P><B>Abstract</B></P> <P> <I>Salmonella</I> contamination of fresh produce is the primary bacterial cause of a significant number of foodborne outbreaks and infections. Bacteriophages can be used as natural antibacterial agents to control foodborne pathogens. However, the rapid development of bacterial resistance to phage infection is a significant barrier to practical phage application. To overcome this problem, we developed a novel phage cocktail consisting of the three phages (BSPM4, BSP101 and BSP22A) that target different host receptors, including flagella, O-antigen and BtuB, respectively. Whole genome sequence analysis of the phages revealed that three phages do not harbor genes involved in lysogen formation or toxin production, suggesting they are safe for use as biocontrol agents in foods. <I>In vitro</I> treatment of the phage cocktail resulted in a significant reduction in the development of bacterial resistance. Phage cocktail treatments achieved 4.7–5.5 log CFU/cm<SUP>2</SUP> reduction of viable cell number in iceberg lettuce and 4.8–5.8 log CFU/cm<SUP>2</SUP> reduction in cucumber after 12 h at room temperature (25 °C). The phage cocktail exhibited good antimicrobial efficiency, suggesting that it could reduce <I>S</I>. Typhimurium contamination of fresh produce. The strategy of developing cocktails of phages that target multiple host receptors can be used to develop novel biocontrol agents of <I>S</I>. Typhimurium.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Receptors of <I>Salmonella</I> Typhimurium-targeting bacteriophages were identified. </LI> <LI> A three-phage cocktail targeting different receptors was developed. </LI> <LI> Simultaneous targeting of three different receptors reduced the development of resistance. </LI> <LI> Phage cocktails represent promising biocontrol agents. </LI> </UL> </P>
Bai, Jaewoo,Kim, Seul I,Ryu, Sangryeol,Yoon, Hyunjin American Society for Microbiology 2014 Infection and immunity Vol.82 No.10
<P><I>Salmonella enterica</I> serovar Typhimurium is a primary cause of enteric diseases and has acquired a variety of virulence factors during its evolution into a pathogen. Secreted virulence factors interact with commensal flora and host cells and enable <I>Salmonella</I> to survive and thrive in hostile environments. Outer membrane vesicles (OMVs) released from many Gram-negative bacteria function as a mechanism for the secretion of complex mixtures, including virulence factors. We performed a proteomic analysis of OMVs that were isolated under standard laboratory and acidic minimal medium conditions and identified 14 OMV-associated proteins that were observed in the OMV fraction isolated only under the acidic minimal medium conditions, which reproduced the nutrient-deficient intracellular milieu. The inferred roles of these 14 proteins were diverse, including transporter, enzyme, and transcriptional regulator. The absence of these proteins influenced <I>Salmonella</I> survival inside murine macrophages. Eleven of these proteins were predicted to possess secretion signal sequences at their N termini, and three (HupA, GlnH, and PhoN) of the proteins were found to be translocated into the cytoplasm of host cells. The comparative proteomic profiling of OMVs performed in this study revealed different protein compositions in the OMVs isolated under the two different conditions, which indicates that the OMV cargo depends on the growth conditions and provides a deeper insight into how <I>Salmonella</I> utilizes OMVs to adapt to environmental changes.</P>
Yun Bai,Jaewoo Shim 현대문법학회 2021 현대문법연구 Vol.109 No.-
Yun Bai and Jaewoo Shim. 2021. English Pronunciation Self-efficacy Sources and Pronunciation Proficiency of Chinese College Learners. Studies in Modern Grammar 109, 105-126. The purpose of this study is to investigate the relationship between the four sources of English pronunciation self-efficacy and English pronunciation proficiency of Chinese college learners of English. A sample of 429 English majors at a college in China was selected. The test scores from a read-aloud task were used as the measure of subjects’ English pronunciation proficiency. The questionnaire was used to collect the data of four English pronunciation self-efficacy sources. The Pearson correlations showed that the four sources were correlated significantly with English pronunciation proficiency. The multiple regression analysis showed that 45% variance in English pronunciation proficiency was explained by the linear combinations of the four sources; however, the nominal variable of gender was not statistically significant in explaining the variance in English pronunciation proficiency. Overall, the significant relationship between English pronunciation self-efficacy sources and English pronunciation proficiency was observed in the present study. Pedagogical implications for teaching English pronunciation were discussed based on the results.
The Relationship between Pronunciation Self-Efficacy Sources and Pronunciation Learning Strategy Use
Yun Bai,Jaewoo Shim,Heechul Lee 한국영어교과교육학회 2021 영어교과교육 Vol.20 No.3
The purpose of this study is to investigate the relationship between the subjects’ four sources of English pronunciation self-efficacy and their pronunciation learning strategy use. The subjects were 429 Chinese English majors from a university in China. The sub-dimensions of the two instruments were first validated through a confirmatory factor analysis (CFA). The group variable (i.e., the three clusters identified by the k-means cluster analysis) was the dependent variable, and the four sources of pronunciation self-efficacy were entered as the independent variables in a discriminant analysis. The results revealed that three out of the four sources of English pronunciation self-efficacy (i.e., ‘enactive mastery experience’, ‘vicarious experience’, and ‘verbal persuasion’) contributed to differentiating the subjects into the three clusters (groups) of high-, low-, and medium users of pronunciation learning strategies, with an overall classification accuracy ratio of 61.6%. Some implications concerning consciousness-raising activities, task repetition, and corrective feedback for teaching English pronunciation were discussed based on the results of the study.
Isolation and characterization of two unrecorded yeast species in the phylum Basidiomycota
Jieun Seok,Jaewoo Bai,Sathiyaraj Srinivasan 국립생물자원관 2024 Journal of species research Vol.13 No.1
The purpose of this study was to isolate and identify wild yeasts from soil samples collected in Seoul and Daejeon, Republic of Korea. To identify wild yeast strains, pairwise sequence comparisons of D1/D2 region of the 26S rRNA gene sequence were done using Basic Local Alignment Search Tool (BLAST). The cell morphologies were observed by phase contrast microscope and carbon source assimilation test were done using API 20C AUX kit. Among the 13 isolated strains, 11 strains were previously reported, but two strains have never been reported from Republic of Korea. The 13 strains were assigned to the phylum Basidiomycota. The two unrecorded yeast strains B2UV-201 and DJ1-5-B-10C belong to the genera Rhodotorula and Rhodosporidiobolus, respectively. The two unrecorded yeast strains are oval shaped and polar budding cells. This research focuses on the morphological and biochemical properties of the two unreported yeast species that have not officially been reported in Korea.
Structural Basis for Cell-Wall Recognition by Bacteriophage PBC5 Endolysin
Lee, Ko On,Kong, Minsuk,Kim, Iktae,Bai, Jaewoo,Cha, Soyoung,Kim, Boram,Ryu, Kyoung-Seok,Ryu, Sangryeol,Suh, Jeong-Yong Elsevier 2019 Structure Vol.27 No.9
<P><B>Summary</B></P> <P>Phage endolysins are hydrolytic enzymes that cleave the bacterial cell wall during the lytic cycle. We isolated the bacteriophage PBC5 against <I>Bacillus cereus</I>, a major foodborne pathogen, and describe the molecular interaction between endolysin LysPBC5 and the host peptidoglycan structure. LysPBC5 has an N-terminal glycoside hydrolase 25 domain, and a C-terminal cell-wall binding domain (CBD) that is critical for specific cell-wall recognition and lysis. The crystal and solution structures of CBDs reveal tandem SH3b domains that are tightly engaged with each other. The CBD binds to the peptidoglycan in a bidentate manner via distal β sheet motifs with pseudo 2-fold symmetry, which can explain its high affinity and host specificity. The CBD primarily interacts with the glycan strand of the peptidoglycan layer instead of the peptide crosslink, implicating the tertiary structure of peptidoglycan as the recognition motif of endolysins.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Phage PBC5 encodes a novel endolysin LysPBC5 against <I>Bacillus cereus</I> </LI> <LI> LysPBC5 recognizes host cell walls via a conjoined tandem SH3b repeat fold </LI> <LI> The SH3b repeat fold interacts with peptidoglycans in a bidentate manner </LI> <LI> LysPBC5 primarily binds to glycan strands of the cell-wall structure </LI> </UL> </P> <P><B>Graphical Abstract</B></P> <P>[DISPLAY OMISSION]</P>