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This Week’s Discoveries | 28 January 2020

Tuesday 28 January 2020
Niels Bohrweg 2
2333 CA Leiden
De Sitterzaal

First lecture, Lorentz Center highlight

The cosmic ballet: spin and shape alignment of haloes and galaxies in the cosmic web. 

Punyakoti Ganeshaiah Veena (RUG and University of Tartu)
 Punyakoti Ganeshaiah Veena is a PhD student at Kapteyn Astronomical Institute and Tartu Observatory. She is one of the participants of the workshop '
The Cosmic Web in the Local Universe' that is being held in the Lorentz Center from 27 January through 31 January.

On the very large scales, galaxies and dark matter in the Universe are distributed in a web-like structure known as the Cosmic Web. This web consists of a wealth of structures such as high-density clusters, elongated filaments, sheets and underdense void regions. The gravitational tidal fields that collapse the initial over-densities to form the cosmic web also induce angular momentum in haloes and galaxies. As a result, we expect a correlation between the cosmic web environment and the properties of dark matter haloes, such as spin. I will show how halo and galaxy spins are aligned in the cosmic web, especially in filaments. I will present the results obtained by extracting the cosmic filaments using state-of-the-art techniques, from very large simulations of the universe: the Planck-Millennium and EAGLE. I will also show that the halo spin-filament alignment is sensitive to the type of filament that the haloes are growing in.

Second lecture

Uncovering the functional dynamics of H-NS protein, the gradient of Enterobacterial pathogens genome

Fredj Ben Bdira (LIC)

As a PhD candidate at Leiden University, dr. Fredj Ben Bdira worked on the ubiquitous family of enzymes b-glucosidases under the supervision of Prof. Marcellus Ubbink. During that period, he used advanced NMR and paramagnetic NMR spectroscopies to study functional dynamics and structural stability of b-glucosidases. His research has revealed novel insights into the role of restricted dynamics of rigid enzymes matrix in processing flexible carbohydrate substrates and in binding to pharmacological chaperones.

After graduation, he joined the group of dr. Remus T. Dame as a post-doc researcher to study the structure-function relationship of H-NS family proteins involved in the dynamic organisation of the enterobacterial genome at an atomic level. In the future, he aims to use the knowledge produced in his current research to find novel strategies to fight multidrug-resistant pathogens. 

Worldwide 2-6 million children die each year from gastrointestinal infections caused by a large number of microorganisms, including enterobacteria such as Salmonella, Shigella, Yersinia and E. coli. A characteristic feature of these enterobacterial pathogens is the organization of their genome by H-NS proteins. These proteins act as a transcription repressor of many genes responsible for bacterial virulence and operate as modulators of multidrug resistance (MDR) phenotype. Key to the physiological functions of H-NS proteins is their ability to form oligomers along DNA, and under specific conditions, to switch to bridging two DNA duplexes. These two DNA binding modes of H-NS proteins are thought to play critical roles in the organization of the genome of enterobacterial pathogens and gene transcription. Nevertheless, the molecular mechanism underlying the switching process and its conservation among H-NS family members remain elusive.

In our studies, we have uncovered the driving forces that govern the modulation of H-NS DNA binding modes at an atomic level, establishing a general paradigm for the molecular mechanistic basis of the function of H-NS proteins. Our findings pave the way for the modulation of the DNA binding modes of H-NS proteins by a new generation of antibiotics, which target the essence of enterobacteria MDR phenotypes, the dynamic organization of their genome.

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