The Great Wall Symposium

The second Great Wall symposium recently held in Lisbon, Portugal featured the latest advances in the field of peptidoglycan metabolism. Over the past several years, the peptidoglycan molecule has received renewed attention. With new technologies available, microbiologists are rethinking aspects of peptidoglycan structure. In addition, microbial genetics is providing new insight into how the cell orchestrates the synthesis, breakdown, and recycling of the molecule. Further, new data are emerging that demonstrate a role for peptidoglycan or peptidoglycan derivatives in communication among bacterial cells of the same species, different species, and between bacterial cells and eukaryotic host organisms. And finally, peptidoglycan is being recognized as a signaling molecule not only in pathogenesis, but also in the normal, beneficial interactions that animals have with their coevolved microbial partners.

The field of the bacterial cell wall really emerged in the 1940s and 1950s with the clinical use of penicillin G and the studies of its mode of action. The 50s–60s led to seminal discoveries on the bacterial cell wall, in particular, the Park nucleotides, precursors of the peptidoglycan, and the penicillin-binding proteins, by Park and Strominger among other researchers. In the 70s, Spratt attributed for the first time a specific role of some of the penicillin binding protein (PBP) in cell shape, while in the 80s, Tomasz dissected the mechanisms of the emerging resistance to β-lactams in major Gram-positive pathogens with the identification of PBP2a in Staphylococcus aureus and the mosaic PBPs in Streptococcus pneumoniae. Despite the importance of the field, the interest waned slowly away in the 90s. The last meeting dedicated to studies on peptidoglycan took place in 1995 in Lago di Garda, Italy and contributions to this meeting were published in two volumes of MDR (Microbial Drug Resistance 1996; Vols. 2 and 3). The remerged interest in the field of peptidoglycan research occurred around the year 2000 with two important discoveries: (1) the characterization of bacterial cytoskeletal proteins and their role in driving cell wall synthesis and the corresponding shape of a bacterium, and (2) the discovery of innate immune receptors both in model systems such as Drosophila (through peptidoglycan recognition proteins) and in mammals (through the Nod proteins) involved in detecting bacteria through the sensing of their peptidoglycan. As a consequence of the rediscovered interest in peptidoglycan by microbiologists, cell biologists, and immunologists, Miguel de Pedro, Joseph Dillard, and Margaret McFall-Ngai organized in Baeza, Spain, October 4–6, 2010, a first meeting exclusively focused on peptidoglycan research. This first small meeting attended by around 50 researchers was a real success and immediately stimulated the organization of a second meeting that took place in Lisbon, Portugal, September 28–30, 2011. The current name of the meeting was inspired by a review paper published in 2006 “Breaching the great wall: peptidoglycan and microbial interactions.”

The symposium was an immediate success as the initial number of participants of 100 had to be expanded to 120 without being able to accommodate all the researchers who were interested in attending. Some of the science presented in the meeting is featured in this special issue of Microbial Drug Resistance that illustrates some of the advances that occurred in the last 16 years since the meeting in Lago di Garda, Italy. The renewed interested in the field is further illustrated with the organization of the third Great Wall Symposium that will take place at the Institut Pasteur in Paris, September 23–25, 2013.