Spatial organization of Clostridium difficile S-layer biogenesis

Surface layers (S-layers) are protective protein coats which form around all archaea and most bacterial cells. Clostridium difficile is a gram-positive bacterium with an S-layer covering its peptidoglycan cell wall. The S-layer in C. difficile is constructed mainly of S-layer protein A (SlpA), which is a key virulence factor for these bacteria and an absolute requirement for disease. Studying the formation and maintenance of the C. difficile S-layer will allow the discovery of specific therapeutic interventions in the future. Here we use microscopy to examine the subcellular localization of S-layer growth and SlpA secretion. We observed formation of S-layer at specific sites that coincide with cell wall synthesis, while conversely the secretion of SlpA from the cell is delocalized. We conclude that this delocalized secretion of SlpA leads to a pool of precursor in the cell wall which is available to repair openings in the S-layer formed during cell growth or following damage.