Research Lab

Bacterial Cell Surfaces and Pathogenesis

Bacterial Cell Surfaces and Pathogenesis

Lab Members

Research Interests

We are focused on understanding how bacteria assemble their cell surface. This process is carried out by a multistep mechanism that ensures (1) the robustness of the bacterial cell surface, which allows bacteria to withstand the intense osmotic pressures they are normally subjected to and (2) the concealment of the peptidoglycan (PGN) molecule, a major component of any bacterial cell surface and a telltale molecule that flags bacteria to the host innate immune system.

The questions currently being tackled are:

  • How do Staphylococcus aureus bacteria conceal their PGN from detection by Drosophila host immune receptors?
  • How do Streptococcus pneumoniae bacteria express their ability to resist beta-lactam antibiotics, which prevent synthesis of the PGN macromolecule, and decorate it with capsular polysaccharides, a major pneumococcal virulence factor?
  • How do plant receptors recognize PGN molecules and discriminate those produced
  • by plant bacterial pathogens vs bacterial symbionts?
Research Highlights
Study of PGN biosynthesis at the division septum of S. aureus

PGN is a macromolecule assembled by several enzymatic activities that take place inside the bacteria (the synthesis of the Park’s nucleotide), at the membrane (the translocation of the PGN precursor across the lipid bilayer) and at the surface (the polymerization of the PGN scaffold). We are determining if PGN hydrolases have a role in concealing the newly synthesized PGN in the division septum from the infected host in clinical S. aureus isolates (Covas et al, in preparation). We have also collaborated with Pinho’s group to determine how PGN synthesis is recruited to the division septum in S. aureus (Monteiro et al, NATURE, 2018).


fig1Representation of the different steps of S. aureus cell division


Study of regulation of PGN hydrolases activity

Bacterial PGN hydrolases are cell wall lytic enzymes that can trim or degrade the PGN macromolecule. Bacteria produce different types of these enzymes in order to regulate their division or prevent recognition by the infected host. The activity of these enzymes needs to be regulated in order to prevent death and lysis of bacteria. We have collaborated with CarballidoLopez’s group and found that the composition of the growth medium induces an alteration of the PGN composition of B. subtilis, namely at the level of amidated meso-diaminopimelic acid in their PGN, which results in deregulation of PGN hydrolysis (Dajkovic et al, MOL MICROBIOL 2017).


fig2Representation of the PGN macromolecule (Top) and the chemical composition of amidated and nonamidated meso-diaminopimelic acid


Representative Projects

  • “Role of the peptidoglycan hydrolases in the interaction of Streptococcus pneumoniae with an infected host”, FCT-MCTES, Total funding: €239,792, Unit funding: €232,292, Sérgio R. Filipe (PI).
  • “Clinical significance of Mycobacterium tuberculosis cell wall structural diversity: contribution to novel mechanisms of antibiotic resistance and relevance towards tuberculosis progression and treatment”, FCTMCTES, Total funding: €238,647, Unit funding: €11,250, Sérgio R. Filipe (Collaborator).
  • “Molecular and cell biology of imipenem resistance in the human enteric pathogen Clostridium difficile”, FCTMCTES, Total funding: €239,862, Unit funding: €9,375, Sérgio R. Filipe (Collaborator).

Selected Publications

Vaz, F; Kounatidis, I; Covas, G; Parton, RM; Harkiolaki, M; Davis, I; Filipe, SR; Ligoxygakis, P. 2019. Accessibility to Peptidoglycan Is Important for the Recognition of Gram-Positive Bacteria in Drosophila. Cell Reports, 27, DOI: 10.1016/j.celrep.2019.04.103
Monteiro, JM; Covas, G; Rausch, D; Filipe, SR; Schneider, T; Sahl, HG; Pinho, MG. 2019. The pentaglycine bridges of Staphylococcus aureus peptidoglycan are essential for cell integrity. Scientific Reports, 9, DOI: 10.1038/s41598-019-41461-1
Catalao, MJ; Filipe, SR; Pimentel, M. 2019. Revisiting Anti-tuberculosis Therapeutic Strategies That Target the Peptidoglycan Structure and Synthesis. Frontiers in Microbiology, 10, DOI: 10.3389/fmicb.2019.00190
Szymczak, P; Filipe, SR; Covas, G; Vogensen, FK; Neves, AR; Janzen, T. 2018. Cell Wall Glycans Mediate Recognition of the Dairy Bacterium Streptococcus thermophilus by Bacteriophages. APPLIED AND ENVIRONMENTAL MICROBIOLOGY, 84, DOI: 10.1128/AEM.01847-18
Carvalho, LCR; Queda, F; Almeida, CV; Filipe, SR; Marques, MMB. 2018. From a Natural Polymer to Relevant NAG-NAM Precursors. Asian Journal of Organic Chemistry, 7, DOI: 10.1002/ajoc.201800592