The Medium Is the Message: Interspecies and Interkingdom Signaling by Peptidoglycan and Related Bacterial Glycans

Abstract

Peptidoglycan serves as a key structure of the bacterial cell by determining cell shape and providing resistance to internal turgor pressure. However, in addition to these essential and well-studied functions, bacterial signaling by peptidoglycan fragments, or muropeptides, has been demonstrated by recent work. Actively growing bacteria release muropeptides as a consequence of cell wall remodeling during elongation and division. Therefore, the presence of muropeptide synthesis is indicative of growth-promoting conditions and may serve as a broadly conserved signal for nongrowing cells to reinitiate growth. In addition, muropeptides serve as signals between bacteria and eukaryotic organisms during both pathogenic and symbiotic interactions. The increasingly appreciated role of the microbiota in metazoan organisms suggests that muropeptide signaling likely has important implications for homeostatic mammalian physiology.

Transcriptional response of Prochlorococcus to co-culture with a marine Alteromonas: differences between strains and the involvement of putative infochemicals

“…First, in all three co-cultures, changes were observed in the expression of genes involved in the biosynthesis or modification of peptidoglycan and lipopolysaccharides (Table 2, Figure 3). Peptidoglycan and lipopolysaccharides are components of the bacterial cell wall and outer membrane, and both have been suggested to mediate cell-cell recognition and signaling (Dworkin, 2014). Similar changes have been observed in different Synechococcus strains in response to co-culture (Tai et al, 2009;Beliaev et al, 2014).…”

A novel STK1-targeted small-molecule as an “antibiotic resistance breaker” against multidrug-resistant Staphylococcus aureus

“…aureus STK1, may allow Inh2-B1 to attain a pose for a stronger and a stable interaction with the catalytic domain of STK1. A recent study has shown that the species-specific PASTA domain and associated free peptidoglycans somehow determine the specificity of the STK enzyme for its activation in response to external stimuli 64 . Our molecular docking analysis of Inh2-derivatives showing the highest affinity (−11.6 kCal/mol) of Inh2-B1 for the kinase domain of STK1 (PDB 4EQM) suggests that the tertiary structure (catalytic pocket) formed by the glycine-rich loop and the surrounding networks of amino acids contribute to the species-specific kinase activity.…”

Analysis of Peptidoglycan Fragment Release

“…Despite the presence of recycling pathways for muropeptides, the assembly and disassembly of cell wall does not represent a closed system, as some fragments of peptidoglycan escape into the environment. These fragments can induce inflammatory responses in hosts, provide protective immune modulatory signals, aid in initiating mutualism, and coordinate bacteria-bacteria interactions (reviewed in [6,7]).…”