Peptidoglycan (PG) is a key component of bacterial cell walls that plays an important role in bacterial physiology, shape, antibiotic resistance, and interactions with hosts. The document discusses understanding PG structure and assembly, using a signaling peptide from PG as a potential antibiotic, and exploring PG's role as a signaling molecule that impacts host homeostasis, disease, and the immune system. Future perspectives include using PG detection to diagnose sepsis, using probiotics to prevent inflammatory diseases, and developing new treatments targeting PG signaling pathways.

1. Bacterial infectious diseases: The PG perspective Ivo G Boneca Group Biology and genetics of the bacterial cell wall Institut Pasteur, INSERM Paris, France CEA CHRU CNRS CPU INRA INRIA INSERM INSTITUT PASTEUR IRD

2. PG a key component of bacterial physiology peptidoglycan Bacterial shape/ physiology Antibiotics resistance Host/Microbe interactions Mesenteric Lymph Nodes Peyer’s Patches Cryptopatches Lymphatics ILFs Gram -

3. Understanding PG structure and assembly How do they work ? How do they determine shape? Model PBP2 MreC SID 116 226 PBP2 (588 aa) N-ter C-ter MreC (248 aa)

6. Understanding PG as a signaling molecule Analysis of the H ost response DNA arrays Fine analysis of PG distribution Structural analysis of circulating 3 H- PG by HPLC Analysis of circulating cells carrying 3 H- PG by AutoMACs Soluble 3 H-PG Homeostasis vs Disease (IBD, sepsis)

7. Studying the PG as a signaling molecule in vivo time 24 h Femur (0.02 cpm/mm 2 ) Stomach (0.24 cpm/mm 2 ) Intestin (0.08 cpm/mm 2 ) 1 h 6 h

9. peptidoglycan Bacterial shape/ physiology Antibiotics resistance Host/Microbe interactions