74 research outputs found
Study of the formation of the view on teachers and the occupational adjustment of joong-cho physical education teachers
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Isolation and Characterization of Bacteriophage SAP4 and Its Endolysin LysSAP4 targeting Staphylococcus aureus
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곡νλΆ, 2015. 8. μ μλ ¬.Staphylococcus aureus is one of the most common foodborne pathogens that cause serious threats to human and animals. Prevalence of antibiotic-resistant S. aureus, such as methicillin-resistant S. aureus (MRSA) and vancomycin-resistant S. aureus (VRSA), increases the necessity of alternative antibacterial agents those can replace traditional antibiotics. Bacteriophage and endolysin have been regarded as new bio-control agents against S. aureus. In this study, bacteriophage SAP4 targeting S. aureus was isolated and characterized. SAP4 is a prophage obtained from S. aureus clinical isolate. It belongs to Siphoviridae family with non-contractile tail and prolonged head, while most staphylococcal phages had icosahedral head. SAP4 had strong lytic activity against S. aureus and its activity was maintained over 29 h. It could infect 7 S. aureus strains including one MRSA and one additional staphylococcal strain (S. haemolyticus) among 18 staphylococcal strains tested. Genome analysis showed that phage SAP4 genome contains 43,120-bp double stranded DNA, encoding 61 open reading frames (ORFs) with no tRNA. Among 61 genes, a putative endolysin gene, which was highly homologous to N-acetyl-muramoyl-L-alanine amidase, was identified. LysSAP4, the endolysin of SAP4, contains two enzymatically active domains (EADs) such as cysteine, histidine-dependent aminohydrolase/peptidase (CHAP) and N-acetyl-muramoyl-L-alanine amidase (MurNAc-LAA, amidase_3) and one cell wall binding domain (CBD) homologous to the SH3b domain. LysSAP4 was highly active between pH 8.0 and 37β in broad salt concentration conditions. Moreover, lytic activity was dependent on divalent metal ions, especially Zn2+. The antimicrobial spectrum of LysSAP4 was broader than that of phage SAP4 that it could specifically kill all staphylococcal strains tested. Also the biofilm was reduced by about 70% with LysSAP4 treatment. CBD of LysSAP4 showed specific binding to staphylococcal strains. Taken together, LysSAP4 is a good candidate as a bio-control agent for S. aureus.ABSTRACT.................................i
CONTENTS.................................iii
I. INTRODUCTION.................................5
II. MATERIALS AND METHODS.................................9
1. Bacterial strains, media and growth conditions.................................9
2. Phage SAP4 isolation and propagation.................................9
3. Transmission electron microscopy (TEM).................................11
4. Bacterial challenge assay.................................11
5. Bacteriophage host range.................................12
6. Receptor analysis.................................12
7. Bacteriophage genomic DNA purification.................................13
8. Full genome sequencing of bacteriophage and bioinformatics analysis.................................13
9. Cloning, overexpression and purification of LysSAP4 and EGFP-LysSAP4_CBD.................................14
10. SyTox kinetic assay.................................15
11. Biofilm reduction assay.................................17
12. GFP fluorescence assay.................................17
III. RESULTS.................................19
1. Isolation and characterization of bacteriophage SAP4.................................19
2. Challenge assay.................................21
3. Host range of bacteriophage SAP4.................................23
4. Receptor determination.................................25
5. Whole genome analysis of bacteriophage SAP4.................................27
6. Identification of a phage endolysin, LysSAP4.................................29
7. Effect of pH, temperature and ionic strength of LysSAP4.................................33
8. Effects of divalent metal ions.................................35
9. Antimicrobial activity spectrum of LysSAP4.................................37
10. Biofilm reduction assay.................................39
11. EGFP-LysSAP4_CBD recombinant expression, purification and binding spectrum of the fusion protein.................................41
IV. DISCUSSION.................................44
V. REFFERENCES.................................49
κ΅λ¬Έμ΄λ‘.................................56Maste
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μ νλ €ν λλ λΆν΄λ½ λ±μ κ²°μ±νμ¬ μλ‘ λμμ μ£Όκ³ λ°λ κ²μ΄ μ’λ€.CHAPTER 1. INTRODUCTION 1
1.1 The Background of the Study 1
1.2 The Purpose of the Study 3
1.3 Research Questions 5
1.4 Organization of the Thesis 6
CHAPTER 2. LITERATURE REVIEW 7
2.1 Factors Affecting Language Learning 7
2.2 Extensive Reading and Reading Motivation 10
2.2.1 Adult Extensive Reading Motivation 11
2.2.2 Possible Demotivation Factors 12
2.2.3 Graded Readers and Motivation 14
2.3 Extensive Reading and Reading Fluency 15
CHAPTER 3. METHODOLOGY 17
3.1 Overall Procedure 17
3.2 Data Collection 18
3.2.1 Interviews 19
3.2.2 Text Messages 21
3.2.3 Reading Fluency Tests 22
3.3 Participants 25
3.3.1 General Information of Participants 25
3.3.2 Ryuβs Background Information 28
3.3.3 Yunβs Background Information 29
3.3.4 Joβs Background Information 31
3.3.5 Jungβs Background Information 32
3.4 Participant Preparation 33
3.5 Reading Materials 34
3.6 The Role of the Researcher 35
3.7 Data Analysis and Interpretation 36
CHAPTER 4. Extensive Reading Experiences of Four Working Men 38
4.1 Ryu: A Musical Composer Who Wants to Write English Lyrics 39
4.1.1 Overall Reading Experiences 42
4.1.2 I Am a Discouraged English Learner with No Grammatical Base .48
4.1.3 Extensive Reading Feels Like Studying 52
4.1.4 Ryuβs Reading Fluency Tests 54
4.1.5 Summary of Ryuβs Experience 56
4.2 Yun: An Office Worker Who is a Bookworm 58
4.2.1 Overall Reading Experiences 60
4.2.2 I Am an Exertive Book Reader 67
4.2.3 Exploring Signs of the Times Make Me Flutter 72
4.2.4 Doing Active Reading Keeps Me Being Interested 74
4.2.5 I Would Like to Read Only Ebooks 76
4.2.6 Yunβs Reading Fluency Tests 78
4.2.7 Summary of Yunβs Experience 80
4.3 Jo: A Researcher Who Wants to Go Abroad for Doctorβs Degree 82
4.3.1 Overall Reading Experiences 84
4.3.2 Lexical Inferencing was Easy for Me 87
4.3.3 I Donβt Know How to Enjoy Literature 90
4.3.4 Being a Fluent Reader is Challenging 96
4.3.5 Extensive Reading is Like Taking Roundabout Route 99
4.3.6 Joβs Reading Fluency Tests 102
4.3.7 Summary of Joβs Experience 104
4.4 Jung: A Banker who Seeks for Better Opportunities 106
4.4.1 Overall Reading Experiences 107
4.4.2 Suspense Genre Helps Me Continue Reading 111
4.4.3 Analytic Learning Style Hinders Inferencing 114
4.4.4 Extensive Reading is Not for Exponential Growth of English 117
4.4.5 Jungβs Reading Fluency Tests 120
4.4.6 Summary of Jungβs Experience 121
CHAPTER 5. CONCLUSION 123
5.1 Major Findings 123
5.2 Pedagogical Implications 126
5.3 Limitations of the Study and Suggestions for Future Research 128
REFERENCES 130
APPENDICES 135
ABSTRACT IN KOREAN 142μ
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