Table 1.

Messenger functions of muropeptides.

PG fragment	Structure	Sensing molecule	Function
Dissacharide tripeptide		PrkC and homologs (STPKs)	Induction of germination (Shah et al., 2008; Dworkin and Shah, 2010) Exit from dormancy (Keep et al., 2006; Mukamolova et al., 2006)
mDAP-type PG (tri-, tetra-, pentapeptides)		NA	Induction of rippling in M. xanthus (Shimkets and Kaiser, 1982)
Monomeric NAG sugar		Ngt1 NA NA	Hyphal growth induction (Alvarez and Konopka, 2007) Antimicrobial induction in P. aeruginosa (Korgaonkar and Whiteley, 2011) and Streptomyces coelicolor (Rigali et al., 2006) CURLI fiber expression in E. coli (Konopka, 2012; Naseem et al., 2012)
Muramyl-dipeptide		Cyr1p	Hyphal growth induction (Xu et al., 2008)
Anhydro-murotetrapeptide (Tracheal cytotoxin, TCT)		NA PGRP2 PGRP3-4	Signaling for morphogenesis (Koropatnick et al., 2004) Hydrolysis of pro-inflammatory PG fragments (Troll et al., 2010) Induction of inflammatory response (Goodson et al., 2005)
Anhydro-muramyltripeptide		AmpR	β-Lactamase induction: AmpC (Uehara and Park, 2002, 2008)
Disaccharide pentapeptide		BlrB	β-Lactamase induction: Amp, Cep, Imi (Tayler et al., 2010)
Dipeptide		BlaI/MecI	β-Lactamase induction: BlaZ, BlaP, MecA (Amoroso et al., 2012)
Dipeptide D-Glu-mDAP (mono and disaccharide peptides containing this structure)		NOD1	NF-κB Innate response activation (Girardin et al., 2003a,b)
Muramyl-dipeptide (disaccharide di-, tri-, tetrapeptides)		NOD2	NF-κB Innate response activation (Fritz et al., 2006; Meylan et al., 2006; Franchi et al., 2009)