Table 1.

Identified effector–immunity pairs.

E–I Pairs	Organisms	Effector Activity	Paper Highlights	Citation
Cell wall Targeting
Tse1, 3/Tsi1, 3	P. aeruginosa	Amidase (Tse1), Muramidase(Tse3)	Tse1, 3 hydrolyze PG and Tsi1, 3 are the immunity proteins	[32]
Tse1(Tae1)/Tsi1(Tai1)	P. aeruginosa	Amidase	Analyzed the crystal structures of Tse1 and Tse1/Tsi1 complex	[39]
Tse3(Tge1)/Tsi3(Tgi1)	P. aeruginosa	Hydrolyse PG	Revealed a calcium-dependent membrane-binding mechanism	[43]
Tae1–4/Tai1–4	B. thailandensis	Amidase	Defined the Tae superfamily	[14]
Tae3/Tai3	R. pickettii	Amidase	Analyzed the structures of Tae3, Tai3 and Tae3/Tai3 complex	[42]
Tae4/Tai4	E. cloacae, S. Typhimurium	DL-endopeptidase	Analyzed the structure of Tae4/Tai4	[33]
			Proved the cross-immunity of T6SS E–I pairs	[44]
Tae4/Tai4	S. Typhimurium	Muramidase	Tae4 contributes to bacteria competition and infection	[45]
Tae/Tai	A. tumefaciens	Target the PG	Indentified Tae/Tai pairs	[58]
VgrG3/TsaB(TsiV3)	V. cholerae	Degrade PG	Identified the VgrG-3 and the antitoxin TsaB	[18]
			Analyzed the structures of native TsaB and the VgrG3C-TsaB complex	[37]
VgrG3/TsiV3(TsaB)	V. cholerae	Disrupt bacterial cell wall	Identified E–I pairs with Tn-seq	[12]
Tge1–3/Tgi1–3	P. protegens	PG glycoside hydrolase	Identified Tge/Tgi Families	[13]
Ssp1, 2/Rap1a, 2a	S. marcescens	Target cell wall	Identified new toxic T6SS pairs	[46]
		PG DL-endopeptidase	Analyzed the E–I pair structures	[47]
Ssp1, 2/Rap1, 2	S. marcescens	Predicted amidases	Identified the Ssp1-6 toxins with proteomic method	[48]
TseH/TsiH	V. cholerae	Predicted amidase	Identified a new E–I pair with secretome analysis	[72]
Membrane Targeting
VasX/TsiV2, TseL/TsiV1(Tle2/Tli2)	V. cholerae	Lipase activity	Identified E–I pairs with Tn-seq	[12]
			The two immunity proteins possess a dual regulatory profile	[50]
Tle1–4, 5(PldA)/Tli1–5	B. thailandensis, et al.	Esterases	Discovered a superfamily of bacterial phospholipase	[16]
PldB/PA5088, PA5087, and PA5086	P. aeruginosa	Phospholipase D	PldB targets the bacterial periplasm and activate eukaryotic PI3K/Akt pathway	[52]
TplE/TplEi(Tle4/Tli4)	P. aeruginosa	Phospholipase A1 and Lipase activity	Toxicity in bacterial periplasm and could induce host cell ER stress and autophagy	[53]
Tle1/Tli1	E. coli EAEC 17-2	Phospholipase A1 and A2 activities	The transport of antibacterial Tle1 is mediated by the C-terminus of VgrG	[51]
Hcp-ET2/ETi2 (Tle1/Tli1)	E. coli STEC004, E. coli PE321	Tle1 Phospholipase	Defined Hcp-ET1-5 and the immunity proteins	[59]
Nucleotides Targeting
Tde1, 2/Tdi1, 2	A. tumefaciens	Nucleases	Indentified Tde/Tdi superfamily	[58]
RhsA, B/RhsIA, B	D. dadantii	Nucleases	Rhs proteins mediate intercellular competition	[15]
Rhs2-CT/RhsI2	S. marcescens	HNH endonuclease	Analyzed the Rhs effectors in intraspecies competition	[34]
Rhs-CT3-8/Rhs-CTI3-8	E. coli STEC004, E. coli PE027	DNase and RNase	Analyzed the Rhs-CTs family	[20]
Hcp-ET1, 3, 4/ETi1, 3, 4	E. coli STEC004, E. coli PE321	HNH-DNase (1), Pyocin S3 (3), Colicin-DNase (4)	Defined Hcp-ET1-5 and the immunity proteins	[59]
Tke2/Tki2	P. putida	Nucleases	Toxic Rhs-type effectors were identified and characterized	[57]
Other effectors
Hcp-ET5/ETi5	E. coli STEC004, E. coli PE321	Papain-like peptidase	Defined Hcp-ET1-5 and the immunity proteins	[59]
Tse2/Tsi2	P. aeruginosa	Arrest bacteria growth	Identified Tse1–3 effectors and immunity protein Tsi2	[17]
Tse2/Tsi2	P. aeruginosa	Induce bacterial quiescence	Structure analysis revealed the interaction mechanism of Tse2/Tsi2	[60]
Tse2/Tsi2	P. aeruginosa	NAD-dependent ADP-ribosylating toxins	Analyzed the structure of Tse2 and Tsi2	[61]
Tse4-6/Tsi4-6	P. aeruginosa	Antibacterial effectors	Proteomics screen for T6SS substrates	[62]
Tse6/Tsi6	P. aeruginosa	NAD(P)+ Glycohydrolase	Analyzed the function, delivery and structure of Tse6 toxin	[64]
Tke1, 3/Tki1, 3	P. putida	NAD(P)+ Glycohydrolase (Tke1), unknown for Tke3	Toxic Rhs-type effectors were identified and characterized	[57]
TseC/TsiC	A. hydrophila	Antibacterial toxicity with a predicted colicin domain	Identified T6SS effector using a conserved chaperone domain	[67]
RhsP1, 2-CT/RhsI1, 2	P. aeruginosa	Antibacterial toxicity	Identified new E–I pairs carried by VgrG	[65]
Rhs-CT1, 2, 9/Rhs-CTI1, 2, 9	E. coli STEC004, E. coli PE027	Metallopeptidase (1, 2) or Deaminase (9)	Analyzed the Rhs-CTs family	[20]
Bfe1, 2/Bfi1, 2	B. fragilis	Antagonism function	T6SS E–I pairs were responsible for antagonism to gut Bacteroidales species	[66]