Table 1. Bacterial strains and plasmids used in this study.

Strain number and strain designation hereafter	Relevant characteristic(s)a	Reference
L. lactis VE17061, control	Wild-type strain (WT)	[34]
L. lactis VE17173, Pil	WT, pilA:pilB:srtC:pilC	ibid
L. lactis VE17148, PilΔA	WT, pilB:srtC:pilC	ibid
L. lactis VE17183, PilΔAΔC	WT, pilB:srtC	ibid
L. lactis VE17190, PilΔB	ΔpilB, pilA:srtC:pilC	ibid
L. lactis VE17191, PilSrtC*	ΔsrtC, pilA:pilB:pilC	ibid
L. lactis VE17176, ΔsrtA psrtA Pil	ΔsrtA, psrtA, pilA:pilB:srtC:pilC, pstrA (pIL2608:strA)	[34,36]

^a The host strain as well as the over-expressed pil operon derivatives are indicated; the pil operon and the topology of the predicted gene products are shown in Fig 1. Genes yhgD, yhgE, yhhA, and yhhB whose function has been characterized [34] are hereafter termed pilA, pilB, srtC, and pilC, respectively while the ylcC gene [36] is termed srtA.

SrtC* designates sortase C whose active site has been inactivated.