Cadaverine Covalently Linked to the Peptidoglycan Serves as the Correct Constituent for the Anchoring Mechanism between the Outer Membrane and Peptidoglycan in Selenomonas ruminantium

In Selenomonas ruminantium, a strictly anaerobic and gram-negative bacterium, cadaverine covalently linked to the peptidoglycan is required for the interaction between the peptidoglycan and the S-layer homologous (SLH) domain of the major outer membrane protein Mep45. Here, using a series of diamines with a general structure of NH(3)(+)(CH(2))(n)NH(3)(+) (n = 3 to 6), we found that cadaverine (n = 5) specifically serves as the most efficient constituent of the peptidoglycan in acquiring the high resistance of the cell to external damage agents and is required for effective interaction between the SLH domain of Mep45 and the peptidoglycan, facilitating the correct anchoring of the outer membrane to the peptidoglycan.