Spatial Reorganization of Histone-like Nucleoid Structuring Proteins Caused by Silver Nanoparticles

Silver nanoparticles (AgNPs) and ions (Ag#) can be the new generation of antibiotics due to their antimicrobial effects against bacteria and other microbes. Many studies have shown that AgNPs and Ag# suppress the growth of bacteria and damage the cell walls of the microbes; therefore, treating bacterial cells with AgNPs may be a promising method to terminate multiresistant bacteria. In this work, the effect of AgNPs with two different surface coatings on the spatial reorganization of histone-like nucleoid structuring (H-NS) proteins in Escherichia coli bacteria was investigated using quantitative super-resolution fluorescence microscopy to understand the toxicity and antimicrobial mechanism of AgNPs. H-NS protein is one of the major DNA-associated proteins in bacteria, serving as a universal regulator. AgNPs inhibited the bacterial growth, changed the morphology of bacteria, and disturbed the membrane of bacteria. More importantly, treating bacteria with AgNPs led to spatial reorganization of H-NS proteins because of the released Ag# ions and changes in the clustering behavior of H-NS proteins. Spatial reorganization at the molecular level was quantified using algorithms based on Voronoi diagrams and tessellation. In addition, Ag# ions released from AgNPs led to the formation of larger and denser clusters of H-NS protein centered in the bacteria. As H-NS is a DNA binding protein, denser clustering of H-NS proteins is likely related to the DNA condensation, which was reported previously in the literature. ©2019 Meaad Alqahtany All Rights Reserved Acknowledgments First and foremost, many thanks to Dr. Wang, my adviser for believing in me and giving me this excellent opportunity to work with him and conduct my research under his supervision with the rest of the lab members. I would like to thank him for mentoring me during these two years and supporting me since day one, on both levels, scientifically and academically. Also, many thanks to the lab team and to everyone who was involved in finishing this project. Thank you very much for making this journey enjoyable and advantageous. Second, many thanks to my committee members: Dr. Mary Savin and Dr. Colin Heyes for their valued comments and suggestions on my research and thesis. Furthermore, I would like to thank my family and my support system for the love and the great wishes that they kept sending to me overseas. Thank you for being by my side all the way even though we were on two different sides of the planet. Special thanks to my aunt Misha who has been my number one role model in life and whom I kept growing up to be like. Thank you for the unconditional love, the unbelievable support and for the unforgettable memories that we had all over the years. Last but not least, no matter what I say, I can’t thank enough King Abdullah bin AbdulAziz for making this possible and for initiating this excellent scholarship program. All appreciation and respect to his majesty for introducing a new era of education to the youth of the Kingdom of Saudi Arabia and for sending us to study all over the globe. Dedication To the bravest woman, I’ve ever known in my entire life. To the woman who I’m proud to be blood to her. This work is dedicated to you. May God rest your soul in peace. Table of