Northwestern University

Fri 2:00 PM

EES Seminar: Marie-Francois Gros

When: Friday, March 9, 2018
2:00 PM - 3:00 PM  

Where: Technological Institute, A230, 2145 Sheridan Road, Evanston, IL 60208 map it

Audience: Faculty/Staff - Student - Post Docs/Docs - Graduate Students

Contact: Tierney Acott   847.491.3257

Group: McCormick - Civil and Environmental Engineering

Category: Lectures & Meetings


Role of a nucleotide second messenger signaling in biofilm formation at aspen roots by the rhizobacteria Pseudomonas fluorescens


Rhizobacteria of the Pseudomonas fluorescens group adopt a range of morphological phenotypes on the rhizoplane of Populus, ranging from micro-colonies to highly structured biofilms. Biofilm-forming bacteria have been found to be beneficial for plant growth, however, the underlying mechanisms governing the formation of biofilm at plant roots is poorly understood. In bacteria, the secondary signaling messenger cyclic diguanosine monophosphate (c-di-GMP) is a central regulator of bacterial transition from motile to biofilm life-styles. This molecule is synthetized by enzymes called diguanylate cyclases (DGCs), degraded by phospho-diesterases (PDEs), and bound by a wealth of effector proteins that regulate specific cellular functions.
The intricate interplay between all the players involved in this signaling pathways is arguably the main hindrance to our understanding of the role of c-di-GMP signaling in biofilm formation and PGP activities in this bacteria. In cells, most proteins exert their activities in association with other proteins to form functional complexes and machineries. We combined the identification of protein complexes involved in c-di-GMP regulatory pathways with a systematic CRISPRi-based functional analysis. We built a high-quality binary protein-protein interaction (PPI) map centered on c-di-GMP signaling in P. fluorescens SBW25 from very high confidence interactions. This PPI network clustered in connected functional modules, revealing functional associations connecting c-di-GMP binding proteins to particular metabolic pathways and cellular machineries relevant with plant-root interactions, such as cell signaling, transcriptional regulations, cell adhesion, and transport of various nutrients. Protein-protein networks centered onto specific signaling pathways represent a useful approach for deciphering plant-microbes interactions.


My Research at Argonne National Laboratory, BIO division, is focused on understanding the regulatory mechanisms underlying plant-microbe interactions using the rhizosphere bacterial model, Pseudomonas fluorescens. I am aiming at deciphering the gene regulatory circuits that control bacterial interactions with plant root, with a particular focus on the mechanisms responsible for the development of biofilms such as found at the surface of plant-roots. Using a combination of proteomic, transcriptomic and genetic approaches I am studying the function of protein-complexes important for biofilm formation in P. fluorescens. My background is molecular microbiology and genetics with expertise in various DNA transactions mechanisms and bacterial cell cycle related processes as well as the signaling pathways that regulate them in B. subtilis. I recently developed genetic tools for the interrogation of gene functions in P. fluorescens and assess their role in the formation and shaping of the biofilms.

In the last years I have focused my interest on understanding the biological function of molecular machines, the mechanisms that control their assembly and the regulation pathways that connect them in the bacterial cell. To tackle this question, I used a multipronged strategy combining the identification of protein complexes in protein-protein networks, their dissection by an edgetic approach and their functional study using microbial molecular genetics tools and fluorescent microscopy. I built protein interaction networks mainly centered on DNA metabolism DNA repair and cell division in the gram positive model bacteria B. subtilis, and elucidated the functional role of protein complexes involved in those processes. To understand the internal workings of protein-protein complexes and how cell processes functionally integrate, I expanded my investigations toward the study of signal transduction, specifically the role of protein phosphorylation by bacterial kinases in B. subtilis. My main objective was to decipher the role of post-translational modifications in the regulation of various DNA related cellular processes during the vegetative life and developmental cycle of B. subtilis. New regulatory pathways, kinases crosstalk as well a novel protein scaffolds were revealed highlighting the existence of signaling cascades akin to those described in eukaryotes.

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