Table 1.

Occurrence of Yts1(-like) and/or Yts2 secretion systems and corresponding substrates in Yersinia and other bacterial species.

	Yts1	Yts2
Expression conditions (in Y. enterocolitica O:8)	In vivo:	No extrinsic expression conditions identified so far
	Expression inferred from colonization defect associated with the lack of yts1E during experimental mouse infection
	In vitro:
	High expression: low temperatures (17°C) and high Mg2+-levels (20–50 mM) in LB medium and diverse minimal media. Activation of pclR, yts1 genes and chiY transcription
	Minimal expression: 37°C in LB and any other tested growth medium. Minimal transcription of pclR, yts1 genes and chiY
Regulators (in Y. enterocolitica O:8)	PclR: overproduction activates chiY transcription under high Mg2+-conditions (20–50 mM)	PypC: overproduction results in pypC transcription (autoregulation)
Known secretion substrates (in Y. enterocolitica O:8 strain 8081)	ChiY (YP_001007736.1)*	No secretion substrates known so far
	EngY (YP_001007806.1)*
	YE3650 (YP_001007019.1)*
Species harboring	Y. enterocolitica O:8	Y. enterocolitica O:8
Yts1(-like) and/or Yts2 secretion system	Y. ruckeri [-GspI]	Y. ruckeri [-GspI]
	Y. aldovae	Y. enterocolitica W22703 (O:9)
	Y. mollaretii [-YE3650]	Y. pestis
		Y. pseudotuberculosis
	Yts1-like secretion systems:	Y. bercovieri [-GspH]
	E. amylovora [-EngY; -YE3650]	Y. frederiksenii [-GspH]
	E. tasmaniensis [-EngY; -YE3650]	Y. intermedia [-GspH]
	E. pyrifolia [-EngY; -YE3650]	Y. kristensenii [-GspH; -PypC]
	S. proteamaculans [-EngY; -YE3650]	Y. rohdei [-GspH; -PypC]
	P. aeruginosa [-PclR; -GspC; -EngY; -YE3650]
	P. putida [-PclR; -GspC; -EngY; -YE3650]

[ ], Indicating missing T2S components or substrates. All Yts2 secretion systems of Yersiniae lack GspS components. An asterisk (

^*) indicates the NCBI Ref. Seq. in parenthesis.