A new sugar for an old phage: A c-di-GMP dependent polysaccharide pathway sensitizes E. coli for bacteriophage infection

Abstract

Bacteriophages are ubiquitous parasites of bacteria and major drivers of bacterial ecology and evolution. Despite an ever-growing interest in their biotechnological and therapeutic applications, detailed knowledge of the molecular mechanisms underlying phage-host interactions remains scarce. Here, we show that bacteriophage N4 exploits a novel surface glycan, NGR, as a receptor to infect its host Escherichia coli. We demonstrate that this process is regulated by the second messenger c-di-GMP and that N4 infection is specifically stimulated by the diguanylate cyclase DgcJ while the phosphodiesterase PdeL effectively protects E. coli from N4-mediated killing. PdeL-mediated protection requires its catalytic activity to reduce c-di-GMP and includes a secondary role as a transcriptional repressor. We demonstrate that PdeL binds to and represses the promoter of the wec operon, which encodes components of the ECA exopolysaccharide pathway. However, only the acetylglucosamine epimerase WecB but none of the other ECA components is required for N4 infection. Based on this, we postulate that NGR is an N-acetylmannosamine-based carbohydrate polymer that is produced and exported to the cell surface of E. coli in a c-di-GMP dependent manner where it serves as a receptor for N4. This novel carbohydrate pathway is conserved in E. coli and other bacterial pathogens, serves as the primary receptor for a range of N4-like bacteriophages, and is induced at elevated temperature and by specific amino acid-based nutrients. These studies provide an entry point into understanding how bacteria use specific regulatory mechanisms to balance costs and benefits of highly conserved surface structures.

Type IV pili is a critical virulence factor in clinical isolates ofPaenibacillus thiaminolyticus

“…The top line shows the conserved c-di-GMP-binding site of the MshEN domain, which consists of tandem 24-aa motifs separated by a 5-aa insert [54]. Aligned sequences include MshEN domains of PilB proteins from Clostridioides difficile [82], Clostridium pefringens [81] Pseudomonas aeruginosa (PA3740) [54, 88] and Myxococcus xanthus (MXAN_5788) [89], and from Escherichia coli NfrB [90, 91]. The bottom two lines show the sequence and secondary structure (H, α-helix) of the structurally characterized MshEN protein from Vibrio cholerae (VC_0405, [54, 92]).…”