TABLE 4.

Transformation, PO4 infection, and twitching motility of P. stutzeri strains with plasmids expressing wild-type and C-terminally hexahistidine-tagged PilA proteins

Strain	Relevant genotype	Plasmida	Transformation frequency with chromosomal his+ DNAb	n	PO4 infectionc	Twitching motilityd
LO15		pUCP19	1.82 × 10−6 (1)	4	+	+
Tf300	pilAI::Gmr	pUCP19	≤2 × 10−9 (≤0.001)	4	−	−
Tf300	pilAI::Gmr	pUCPA1	1.55 × 10−6 (0.85)	2	+	+
LO15		pUCPA1	1.60 × 10−6 (0.88)	2	+	+
Tf300	pilAI::Gmr	pUCPA1Ha	≤1 × 10−9 (≤0.0005)	2	ND	ND
Tf300	pilAI::Gmr	pUCPA1Hs	1.87 × 10−6 (1.03)	3	(+)	−
Tf590	pilT::KmrpilAI::Gmr	pUCPA1Hs	1.11 × 10−6 (0.61)	3	−	−
Tf59	pilT::Kmr	pUCP19	≤1 × 10−9 (≤0.0005)	4	−	−
Tf59	pilT::Kmr	pUCPA1	≤1 × 10−9 (≤0.0005)	2	ND	−

^aThe pUCP19 vector contains the pilAI⁺ gene in pUCPA1, the pilAI allele encoding six additional C-terminal histidine residues in pUCPA1Ha, or the pilAI allele encoding six histidine residues substituting for the six C-terminal amino acids in pUCPA1Hs. 

^bPlate transformation of the hisX1 strains was performed with 0.5 μg of chromosomal his⁺ DNA per assay. The experiments were performed in the presence of 1 mg of ampicillin ml⁻¹ to select for maintenance of the pUCP-derived plasmids. The high ampicillin concentration decreased the transformability of LO15(pUCP19) about fivefold. The numbers in parentheses are transformation relative to that with LO15(pUCP19). 

^c+, confluent lysis; −, no plaque; (+), single plaques. 

^d−, no twitching zones after 10 days at 37°C.