Microbial Physiology

Summary

Bacterial survival depends on membrane lipid homeostasis and on the ability to adjust lipid composition to acclimatize the bacterial cell to different environments. Thus, it is clear that an understanding of these processes is fundamental to microbiology, including industrial and clinical microbiology, and ultimately for understanding cell signaling mechanisms conserved in multicellular organisms. Our laboratory investigates the mechanisms by which model and pathogenic Gram-positive bacteria control the biophysical properties of their membrane phospholipids in response to extra and intra-cellular signals. Our discoveries are expected to provide unique targets for more effective treatments of Gram-positive bacterial infections.

Research Lines

Lipid metabolism in Gram positive bacteria

Our research program centers on prokaryotic lipid metabolism. The organism studied is Bacillus subtilis due to the fact that this bacterium is the paradigm of Gram-positive bacteria and possesses a sophisticated genetics system. A central theme of our lab is to understand the genetic biochemical mechanisms that regulate the synthesis of membrane phospholipids. Our current research focuses on defining the regulatory signals and protein-protein interactions that regulate the biosynthesis of fatty acids and to understand how this pathway is coordinated with environmental stresses and cell differentiation. Our approaches to the problems studied are genetics, molecular cloning, protein purification and enzymology. We also have discovered in B. subtilis a new biosynthetic pathway for the key coenzyme lipoic acid. This pathway requires fatty acid biosynthesis and is conserved in many Gram-positive pathogens. Our research project is also relevant to the identification of new targets for anti-bacterial compounds and their development. Recently, our group established cooperation programs with laboratories that are performing structure based design inhibitors of lipid synthesis in Gram positive bacteria.

Mechanistic and Structural Basis of Thermosensing in Bacteria

Thermosensors are ubiquitous integral membrane proteins found in all kinds of life. They are involved in many physiological roles, including membrane remodeling, chemotaxis, touch and pain, but the mechanisms by which their transmembrane (TM) domains sense and transmit temperature signals is largely unknown. The histidine kinase DesK from Bacillus subtilis is the paradigmatic example of a membrane-bound thermosensor suited to remodel membrane fluidity when the temperature drops below~30°C, providing, thus, a tractable system for investigating the mechanism of TM-mediated input-output control of thermal adaptation. The long term goal of this research line is to determine in molecular detail how the TM segments of the signaling protein DesK act as sensors and how they are able to transmit this information to the catalytic cytoplasmic domain. This requires the understanding of two interrelated processes, the TM rearrangements that adjust the signaling state of DesK and the membrane associated events that induce protein motion. We plan to study these problems by combining functional methods (biochemical and in vivo analysis) with biophysical techniques (crystallography and spectroscopy).

Functional Characterization of acyl-lipid desaturases from Bacillus sp. Molecular basis of the reaction mechanism

The biosynthesis of unsaturated fatty acids is initiated by desaturases. Desaturases are a family of enzymes that introduce a double bond at specific positions into fatty acids of defined chain lengths being one of the major determinants of the monounsaturated fatty acid composition of membranes and vegetable oils. The importance of these enzymes in unsaturated fatty acids biosynthesis and the unique chemistry of the reaction that they catalyze have focused our interest in understanding how they introduce the double bond into fatty acids. We use as models the Bacillus genus enzymes

Selected Publications

  • Albanesi D, Reh G, Guerin ME, Schaeffer F, Debarbouille M, et al. (2013) Structural Basis for Feed-Forward Transcriptional Regulation of Membrane Lipid Homeostasis in Staphylococcus aureus. PLoS Pathog 9(1): e1003108. doi:10.1371/journal.ppat.1003108
  • Chazarreta-Cifre, L, Martiarena, L., de Mendoza, D. and Altabe, S. G. (2011) Role of ferredoxin and flavodoxins in Bacillus subtilis fatty acid desaturation. J. Bacteriology 4043-4048.
  • Martin, N., Christensen, Q., Mansilla, M. C., Cronan, J. E. and de Mendoza, D. (2011) A Novel Two-Gene Requirement for the Octanoyltransfer Reaction of Bacillus subtilis Lipoic Acid Biosynthesis. Mol. Microbiol. 80, 335-349.
  • .Cybulski, L. E., Martin, M., Mansilla, M. C., Fernandez, A. and de Mendoza, D. (2010) Membrane Thickness Cue for Cold Sensing in a Bacterium. Curr. Biol. 20, 1539-1544.
  • Martín, N, Lombardía, E., Altabe, S. de Mendoza, D. and Mansilla, M. C. (2009) A Mutant in lipA (yutB), encoding Lipoic Acid Synthase, Provides Insight into the Interplay Between Branched-Chain and Unsaturated Fatty Acids Biosynthesis in Bacillus subtilis. J. Bacteriology 191, 7447-7455
  • Albanesi, D., Martín, M., Trajtenberg, F., Mansilla, M. C., Haouz, M., Alzari, P., de Mendoza, D. and Buschiazzo, A. (2009) Structural plasticity and catalysis regulation of a thermosensor histidine kinase Proc. Natl. Acad. Sci. (USA) 106, 16185-16190.
  • Schujman, G.E., Guerin, M., Buschiazzo, A., Schaeffer, F., Llarull, L. I., Reh, G.,Vila, A.J., Alzari, P. M., and de Mendoza, D. Structural basis of lipid biosynthesis regulation in Gram-positive bacteria (2006) EMBO J. 25, 4074-4083.
  • Albanesi, D., Mansilla, M.C and de Mendoza, D. (2004) The Membrane Fluidity Sensor DesK of Bacillus subtilis Controls the Signal Decay of its Cognate Response Regulator. J. Bacteriol. 186, 2655-2663
  • Schujman, G., Paoletti, L, Grossman, A. and de Mendoza, D. (2003) FapR, a bacterial transcription factor involved in global regulation of membrane lipid biosynthesis. Dev. Cell. 4, 663-672.
  • Diaz, A. R. Mansilla, M. C. Vila, A. J. and de Mendoza, D. (2002) Membrane Topology of the Acyl-Lipid Desaturase from Bacillus subtilis. J. Biol. Chem. 277, 48099-48106.
  • Cybulski, L. E., Albanesi, D., Mansilla, M. C., Altabe, S., Aguilar, P. S. and de Mendoza, D. (2002) Mechanism of membrane fluidity optimization: isothermal control of the Bacillus subtilis acyl-lipid desaturase. Mol. Microbiol. 45, 1379-1388.
  • Aguilar, P., Hernandez-Arriaga, A. M., Cybulski, L., Erazo, A. C. and de Mendoza, D. (2001) Molecular basis of thermosensing: a two component signal transduction thermometer in Bacillus subtilis. EMBO J. 20, 1681-1691.

Collaborators

  • Dr. Pedro Alzari. Institute Pasteur (Francia).
  • Dr. Alejandro Buschiazzo. Instituto Pasteur de Montevideo (Uruguay).
  • Dr. Alejandro Vila. IBR.

Grants

  • Agencia Nacional de Promoción Científica y Tecnológica (ANPCyT).
  • Howard Hughes Medical Institute (HHMI).
  • Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET).

Director

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de Mendoza, Diego
Core CCT
Email: demendoza@ibr-conicet.gov.ar
Phone: +54 341 4237070
Office Extension: 634
Laboratory Extension: 621

Researchers

  • Daniela Albanesi
  • Silvia Graciela Altabe
  • María Cecilia Mansilla

Postdoctoral fellows

  • Celina Galles
  • Emilio Saita

Doctoral fellows

  • Pilar Fernández
  • Antonela Lavatelli
  • Federico Machinandiarena
  • Gastón Prez

Undergraduate Students

  • Natalí Rasetto

Imágenes

Mecanismo de acción de FapR, un regulador global de la síntesis de lípidos en bacterias Grampositivas, muchas de ellas patógenos importantes para los humanos.

Mecanismo molecular para la regulación de las actividades catalíticas del sensor de temperatura DesK de Bacillus subtilis.