TABLE 1.

Characteristics of bacterial strains, plasmids, and primers used in this study

Strains, plasmids, and primers	Characteristics or sequencea	Source or reference
Strains
E. coli DH5αF′	F′ endA1 hsdR17 (rK− mK+) supE44 thi-1 recA1 gyrA (Nalr) relA1 Δ(lacZYA-argF) U169 deoR [φ80dlacδ(lacZ)M15]	20
E. coli HB101	F′ Δ(gpt-proA)62 leuB6 supE44 ara-14 galK2 lacY1 Δ(mcrC-mrr) rpsL20 (Strr) xyl-5 mtl-1 recA13	21
E. coli β2155	thrB1004 pro thi hsdS lacZΔM15 (F′ lacZΔM15 laclqtraD36 proA+ proB+) Δdap::erm (Ermr)	6
11 A. pleuropneumoniae     serotype 2 isolates	Strain collection; Institut für Mikrobiologie und Tierseuchen; all strains are obtained from diseased pigs in Northern Germany	This work
A. pleuropneumoniae     C5934	A. pleuropneumoniae serotype 2 clinical isolate from the lung of a diseased pig in northern Germany	This work
A. pleuropneumoniae     C5934ΔureC	Unmarked urease-negative knockout mutant of A. pleuropneumoniae C5934	This work
A. pleuropneumoniae     C5934ΔureCΔapxIIA	Unmarked ApxIIA-negative knockout mutant of A. pleuropneumoniae C5934ΔureC	This work
Plasmids
pBluescript SK	E. coli cloning vector carrying an ampicillin resistance determinant	Stratageneb
pGH432	E. coli cloning vector carrying an ampicillin resistance determinant and a tac promoter transconjugation vector based on pBluescript SK with mobRP4, polycloning site, kanamycin resistance, and transcriptional fusion of the omlA promoter with the sacB gene	9
pBMK1		19
pBMKUΔ1	pBMK1 carrying the ureC gene with an internal SphlI-BstE deletion	19
pBMKAΔ1	A PCR fragment obtained with the primers apxIIAU and apxIIAL was restricted with BamHI and Sadl and ligated into pBluescript tSK, resulting in plasmid pBAPX3; plasmid pBAPX3 was restricted with Nco1 and BglII, blunt ended with Klenow fragment, and religated; the truncated apxIIA gene was removed	This work
Primers
ureC2	GTAAGG ATCC ATTAACAATC CCACGCAGTC AGTAT; primer with internal BamHI site (underlined) comprising positions 997 to 1022 of the urease operon	19
ureX	TCATGTCGAC TAGAACAAGA AATAACGCTG TGCAA; primer with internal Sall site (underlined) comprising positions 2686 to 2711 of the urease operon	19
apxllAU	CTTTGGATCC AAAAATCACT TTGTCATCAT; primer with internal BamHI site (underlined) comprising positions 782 to 811 of the apxIICA genes	This work
apxllAL	CAATGTCGAC ATTTACACCA TAGGATTGCT; primer with internal SalI site (underlined) comprising positions 3670 to 3699 of the apxIICA genes	This work

^aNal^r, nalidixic acid resistant; Erm^r, erythromycin resistant; Str^r, streptomycin resistant.

^bStratagene Europe, Amsterdam, The Netherlands.