Structural and functional studies on bacterial secretion systems using cryo-electron microscopy

Abstract

Bacterial secretion systems are large membrane structures (in the range of MegaDaltons) formed by multi-protein complexes. To date, nine secretion systems have been identified and characterized (in some cases partially) in a small number of all bacterial species, from which scientists and researchers seek information to understand other species or system under investigation. It is seen that some of these secretion systems can be quite versatile depending on the lifestyle of their hosts, mediating the horizontal transfer of genetic material (conjugation) between bacterial cells, or carry effector proteins into the extracellular milieu or directly into the interior of other cells (both prokaryotic and eukaryotic) with beneficial or harmful effects on the target cells. Also, the same species can carry more than one of these systems, or even contain more than one copy of one of them, showing a high degree of complexity and plasticity. Therefore, secretion systems are important determinants for bacterial adaptation, competition and survival in various environmental niches.In this project, we propose to study the molecular structures and to deepen into the physiological relevance of one of these bacterial nanomachines in less studied models (yet not less relevant), specifically that necessary for pathogenic and symbiotic interactions with plants. This project mainly aims to determine the structures and mechanisms of action of these nanomachines. For that, it involves the use of electron microscopy, a technique that has been revolutionizing the Structural Biology in recent years, as well as other techniques of the field, such as nuclear magnetic resonance (NMR), X-ray crystallography, and small-angle X-ray scattering (SAXS); and computational strategies, especially docking simulations and molecular dynamics, as complementary approaches and tools. At the same time, our studies will employ a variety of other methods and techniques, such as the characterization of knockout strains, gene expression analysis, fluorescence microscopy and bioinformatics. At human resources level, this project assumes training of undergraduate and graduate students, at the same time that promotes collaborations with researchers here in Brazil and abroad, seeking to form a broad self-reliant research network. Therefore, we intend to develop an innovative and highly interdisciplinary working project to reveal the structure and functioning of large membrane-associated protein complexes with biological interest. (AU)