Title Page

Contents

Abstract 10

Ⅰ. INTRODUCTION 13

Ⅱ. MATERIALS AND METHODS 18

1. Data collection and preparation 18

2. Molecular docking and virtual screening 18

3. Compounds 19

4. Bacterial strains and culture conditions 19

5. Phenotypic assay 20

6. OxyR redox status assay 20

7. β-Galatosidase assay 21

8. Evaluation of antibacterial efficacy 21

9. Evaluation of toxicity 22

10. Determination of Minimal Lethal Concentration (MLC) 22

11. Measurement of Antibacterial Activity 23

12. Serial passage assay 23

13. Measurement of synergy 24

14. Statistics 24

Ⅲ. RESULTS 25

1. Virtual screens for the chemical hits based on the OxyR structure 25

2. P. aeruginosa displays serial dilution defects by OX14, 4 and 6 29

3. OxyR-mediated transcriptional regulation is impaired by OX14 33

4. OX14 displays antibacterial efficacy against P. aeruginosa 38

5. NQ14 shows reduced toxicity 40

6. NQ14 shows broadened antibacterial spectrum 42

7. NQ14 activity does not fully involve ROS formation, suggesting multiple modes of action (MoAs) 46

8. No resistance emergence was observed by NQ14 49

9. NQ14 and OX14 show synergy in P. aeruginosa 51

Ⅳ. DISCUSSION 53

Ⅴ. CONCLUSION 58

REFERENCES 60

ABSTRACT IN KOREAN 69

Table 1. Virtual screening results showing the 10 selected compounds 27

Table 2. Bacterial strains and plasmids used in this study 28

Fig. 1. Experimental validation of the selected compounds 31

Fig. 2. Structural modeling of the interactions between OX14 and OxyR 32

Fig. 3. Redox cycle of OxyR in the presence of OX14 36

Fig. 4. Antibacterial efficacy of OX14 against bacterial pathogens 39

Fig. 5. Toxicity assessment of c5 and NQ14 41

Fig. 6. Antibacterial spectrum of c5, NQ14 against bacterial pathogens 44

Fig. 7. Antibacterial efficacy of c5 and NQ14 45

Fig. 8. Antibacterial activity under ROS-compromising conditions 47

Fig. 9. Resistance evaluation of c5 and NQ14 50

Fig. 10. Synergy effect of NQ14 and OX14 52