TABLE 1.

QS signals and their characterization in marine microorganisms

QS signal		Producing species	Chemical structure	Physical properties	Molecular synthase	Regulated protein	Ecological function	References
AI-1 short-chain molecules	C4-HSL	Vibrio harveyi	Homoserine lactone (HSL) ring with a variable acyl side chain.	Molecular weight: from 171.9 Da for a C4- to 367.57 Da for an unsubstituted C 18-AHL (Decho et al., 2011). Solubility: low-molecular-weight AHLs tend to be relatively water soluble, and it is unlikely that communal responses based on their presence would ever be limited by their solubility. However, as molecular weights increase significantly above 520 g/mol, the saturation concentration of the AHL is expected to drop below 1μM AHL (Decho et al., 2011). Diffusivity: from 10 to 78 μm AHL (Decho et al., 2011). Dispersion: from 10 s micrometers to 100 s micrometers AHL (Decho et al., 2011).	LuX-M	LuxR type protein	Bioluminescence	Waters and Bassler (2005)
		Pseudomonas aeruginosa			RH II		Biofilm maturation	Waters and Bassler (2005)
		Aeromonas hydrophyla			Ahy I Asa I		Biofilm formation, Enzyme production	Tebben et al. (2011)
		Serratia marcescens			SWrI		Swarming	Miller and Bassler (2001)
	C6-HSL	Erwinia stewartii G−			LuXI	LuxR type protein	Exopolysaccharide	Watson et al. (2002)
		Vibrio fischeri G−					Light production	Nealson et al. (1970)
		P. fischeri G−					Virulence	Eberhard et al. (1981)
		A. salmonicida			Ahy I	LuxRtype protein	Biofilm formation	Swift et al. (1999)
		Chromobacterium Violaceum			CV I		Violacein, antibiotics, and enzyme production	Cha et al. (1998)
		Yersinia enterolcolitica, Y. pseudotuberculosis			Yen I, Yps I		Motility aggregation	Miller and Bassler (2001)
		Vibrio sp. (algae-associated)			LuxI		Settlement activity	Taylor et al. (2007)
		Vibrio alginolyticus			LuxI		/	Huang et al. (2007)
	C8-HSL	Agrobacterium tumefaciens			Tra I		Virulence factors	Fuqua et al. (2001)
		Y. pseudotuberculosis			Yps I		Potential regulate cells wimming	Miller and Bassler (2001)
		Roseobacter spp., Marinobacter sp.			/		/	Taylor et al. (2007)
AI-1 long-chain molecules	C10-HSL	Vibrio anguillarum			Van I	LuxR	Virulence	Defoirdt et al. (2004)
	C12-HSL	Vibrio alginolyticus			Las I	LuxR	Virulence formation	Pearson et al. (1994)
					/	LuxR	/	Huang et al. (2007)
	C14-HSL	Roseobacter sp.			/	LuxR	/	Mohamed et al. (2008)
AI-2	Furanosyl borate diester	Vibrio harveyi	The proposed structure contains two fused five member rings containing one boron atom bridging the diester.	/	Ai-2		Bioluminescence	Bassler et al. (1993)
		V. cholerae			Ai-2		Virulence	Chen et al. (2002)
		V. harveyi			Ai-2		Virulence	Henke and Bassler (2004)
	2-methy-2,3,3,4-tetrahydroxytetrahydrofuran	V. parahaemolyticus			Cqs A		Virulence	Miller et al. (2002)
		V. cholerae			Ai -2		Virulence	Miller et al. (2004)
		Salmonella enterica					Virulence gene expression	Sperandio et al. (2001)
		Escherichia coli					Type II secretion	Day and Maurelli (2001)
		Shigella flexneri			LupX		Virulence factor virB expression	Mcnab et al. (2003)
		Streptococcus pordonii					Biofilm formation	Li et al. (2002)
AI-3		E. coli, Xanthomonas campestris	DSF:cis-11-methyl-2-dodecenoic acid.	/	LuxS	Lux P/Q type protein	Biofilm formation	Barber et al. (1997)
						Lux O type protein, mRNA-dependent regulation, such as 5RNAs		Reading and Sperandio (2006); Wang et al. (2004)
Peptide autoinducers	Cyclic dipeptides	Pseudomonas sp. Streptomyces griseus Staphylococcus aureus	Diketopiperazines (DPKS)* cyclo (L-Ala-L-Val) and cyclo (L-Pro-L-Tyr).	/	LuxR		Activates AHL biosensors. *: the induction threshold for DKPS is higher than AI-1, which indicates that DKPS may not have a significant role in the marine environment	Degrassi et al. (2002)
	Butyrolactonase							Waters and Bassler (2005)
	Thiolactone							Lyon et al. (2000); Zhang and Dong (2004)
Others	Bradyoxetin	Bradyrhizobium japonicum G−, Rhizobium sp., Alphaproteobacteria sp., Pseudomonas aeruginosa	2-{4-[[4-(3-aminooxetan-2-yl)phenyl](amino)methyl]phenyl} oxetan-3-yl amine.	/	Nod gene	Nod gene	Nitrogen-fixing	Loh et al. (2002a,b)
	Hydroxy palmitic acid methyl ester	Ralstonia solanacearum			PhcS-phcR	Iron concentration	Polysaccharide biosynthesis	Flavier et al. (1997)
	Cys-11-methyl-2-dodecenoic acid	Xanthomonas campestris			/		Virulence	Zhang and Dong (2004)
	Non-identified compounds	Algae symbiotic bacterium			/		Competence, Morphogenesis	Decho et al. (2011)