IPLS Seminar - Dr. Joshua Milstein

Title: Chromosome Packaging and Gene Silencing by Nucleoid Associated Proteins in Bacteria

Abstract: Nucleoid associated proteins play a dual role in both packaging the bacterial chromosome and regulating gene expression. The heat-stable nucleoid structuring protein (H-NS), for instance, can form extended nucleoprotein filaments when bound that act to loop and bridge DNA. However, H-NS is also known to act as a global transcriptional regulator and plays a key role in silencing xenogeneic DNA acquired by lateral transfer. In fact, H-NS acts to regulate of the majority of pathogenicity islands within both infectious Salmonella and E. coli bacteria. We have used optical tweezers to show that tension within the bacterial chromosome can cause the DNA, when bound by H-NS, to condense into a stable nucleoprotein bundle. Likewise, our recent efforts with quantitative super-resolved localization microscopy are providing insight into how the spatial reorganization of H-NS, within the nucleoid, allows the bacteria to respond and adapt to environmental stress.