Molecular and Structural Microbiology

Research lines

Signaling and regulation in microorganisms
We are particularly interested in two component systems (TCS) in bacteria. TCSs are central in mediating signaling and regulation, almost ubiquitous in prokaryotes and archaea, they are also present in fungi and plants. Other regulatory proteins, such as one component systems, are also being studied. The general question behind this line of research is: how do cells use these sensory and regulatory proteins to detect extra- and intra-cellular signals, and then regulate specific functions? To answer this question, saprophytic bacteria (such as Bacillus subtilis and Leptospira biflexa) are studied, as well as pathogenic ones (Leptospira interrogans, L. borpetersenii, L. noguchii, Enterococcus faecium, Mycobacterium tuberculosis). In these models, several key biological processes are studied, such as the regulation of lipid synthesis (Albanesi et al., Proc Natl Acad Sci USA 2009, 106: 16185, Trajtenberg et al., J Biol Chem 2010, 285: 24892, Trajtenberg et al. al., mBio 2014, 5: e02105; Trajtenberg et al., eLife 2016, 5: e21422; Imelio et al., Bio-protocol 2017, 7: e2510; Lara et al., 2018 submitted), heme metabolism (Morero et al., Mol Microbiol 2014 , 94: 340), or virulence in pathogenicity (Adhikarla et al., Front Cell Infect Microbiol 2018, 8:45).

Molecular and structural biology of Leptospira
Different species of Leptospira cause leptospirosis. This zoonosis is the most widespread one around the world, reemerging as an important problem in human and animal health. In Uruguay, it is a significant issue, provoking cattle abortions and reproductive failure, and transmitting to humans causing acute disease. Our lab wants to elucidate the molecular mechanisms that determine and/or regulate virulence and pathogenicity in Leptospira. There are currently two main projects to do this: the study of the motility apparatus and systematic efforts to isolate and type local Leptospira strains in Uruguay.

i- The motility apparatus of Leptospira. Active translational motility of leptospira (swimming) is central for the virulence of the pathogenic species that cause leptospirosis. The essential organelle used for swimming is the flagellum. Our lab is currently studying the detailed molecular architecture of the flagellar appendage. The filament of these spirochetes’ flagella is confined within the periplasm, a unique feature shared by all Spirochetes, including bacteria like Treponema pallidum (the agent of syphilis) or Borrelia burgdorferi (Lyme disease). In collaboration with the Ko and Sindelar labs in Yale University, as well as the Picardeau lab at the Institut Pasteur (Paris), we have shown that the flagellar filament from Leptospira is much more complex compared to better-known bacterial models used so far as a paradigm of swimming motility in bacteria. As an example, filaments from Salmonella and other Enterobacteria are built as homopolymers of a single protein species (flagellin), whereas Leptospira comprise at least eight different proteins polymerized into the periplasmic filament assembly (Wunder et al., Mol Microbiol 2016, 101: 457; San Martin et al., Acta Crystallogr F 2017, 73:123; Wunder et al., Front Cell Infect Microbiol 2018, 8:130). We have recently crystallized two new proteins from both pathogenic and saprophytic Leptospira spp. (San Martín et al., Acta Crystallogr F 2017, 73:123),and solved their 3D structures (unpublished results), revealing novel protein folds. We are now moving forward towards their physiological interactions and interaction partners, enabling for the flagellar filament role in spirochete motility.

ii-Isolation and typing of autochthonous Leptospira spp. strains. This line is being developed in the context of a multicentric collaborative project, aims to isolating native strains from Leptospira spp. from biological samples obtained from infected cattle and other animal reservoirs. These isolates are typed by complementary techniques: classic serologic methods and novel molecular approaches, ultimately achieving greater sensitivity and specificity (Zarantonelli et al., PLoS Negl Trop Dis 2018, 12:e0006694). This effort has led to the creation of a biobank of strains of Leptospira, which up to now was not available in Uruguay, reporting the identity of the serovars that circulate in natural infections. This biobank will be useful in the formulation of more efficacious vaccines, in the improvement of diagnostic methods, as well as in further investigations of leptospirosis in Uruguay.

Collaborations
Our lab works in collaboration with Dr. Hugo Gramajo (Institute of Molecular and Cellular Biology, IBR, Rosario, Argentina) and his team, to elucidate crystallographic structures and mechanisms of action of Mycobacterium tuberculosis transcription factors (one component regulator systems), playing essential roles in regulating fatty acid metabolism in this pathogen.
We also collaborate with Dr. Mathieu Picardeau (Institut Pasteur, Paris, France) and Dr. Albert Ko (Yale University, New Haven, USA) on motility of Leptospira and pathogenesis mechanisms of these bacteria at the molecular level.
In addition, our lab integrates a multicentric consortium in Uruguay, working together with teams from the Veterinary Laboratories Division (“Miguel C Rubino” DILAVE) of the Ministry of Livestock, Agriculture and Fishery (Alejandra Suanes, Rodolfo Rivero), National Institute of Agricultural Research (Franklin Riet), Hygiene Institute at the Medical School (Felipe Schelotto), addressing problems of isolation, typing, diagnostics and genomics of Leptospira.