TABLE 1.

Strains and plasmids used for this study^a

Strain or plasmid	Key features	Reference
Strains
E. coli TG1	supE hsd Δ5 thi Δ(lac-proAB) F′ (traD36 proAB-lacZΔM15)	16
S. aureus RN4220	Avirulent mutant of NCTC 8325-4 that accepts foreign DNA	38
S. aureus RN6390	Virulent laboratory strain derived from NCTC 8325	38
S. aureus COL	Highly methicillin-resistant clinical isolate	54
S. aureus RN6390 htrA1	RN6390, htrA1::cat Cmr	This work
S. aureus RN6390 htrA2	RN6390, htrA2::spc Spcr	This work
S. aureus RN6390 htrA1htrA2	RN6390, htrA1::cat htrA2::spc Cmr Spcr	This work
S. aureus RN6911	RN6390, Δagr::tet Tetr	39
S. aureus COL htrA1	COL, htrA1::cat Cmr	This work
S. aureus COL htrA2	COL, htrA2::spc Spcr	This work
S. aureus COL htrA1htrA2	COL, htrA1::cat htrA2::spc Cmr Spcr	This work
S. agalactiae NEM 316	Virulent strain that produces CAMP factor	17
Plasmids
pMAD	Eryr Ampr; thermosensitive plasmid in S. aureus derived from pRN5101 and containing the bgaB gene	M. Débarbouillé et al., Pasteur Institute, personal communication
pMAD::htrAlimcat	pMAD containing an internal fragment of the S. aureus htrA1 gene interrupted by insertion of a chloramphenicol resistance cassette (cat); used for construction of the S. aureus RN4220 htrA1 mutant; Eryr AmprbgaB	This work
pMAD::htrA2spc	pMAD containing the S. aureus htrA2 gene interrupted by the insertion of a spectinomycin resistance cassette; used for construction of the S. aureus RN4220 htrA2 mutant; Eryr AmprbgaB	This work

^aSee Materials and Methods for intermediate strain and plasmid constructions.