TABLE 1.

Bacterial strains and plasmids used in this study

Strain or plasmid	Strain collection no.	Relevant characteristicsa	Reference or source
P. fluorescens
Pf-5	JL4474	P. fluorescens Pf-5 rhizosphere isolate; Plt+, Ina−	23
Pf-5 iceC+	JL4303	Pf-5 (pJEL1703); Kmr, Plt+, Ina+	34
Pf-5 pltE::inaZ	JL4365	pltE::Tn3-nice derivative of Pf-5, Plt−, Ina+, Kmr	30
Pf-5 pltB::inaZ	JL4389	pltB::Tn3-nice derivative of Pf-5, Plt−, Ina+, Kmr	30
Pf-5 pltF::inaZ	JL4390	pltF::Tn3-nice derivative of Pf-5, Plt−, Ina+, Kmr	30
Pf-5 rpoS::lacZ	JL4489	rpoS::lacZ derivative of Pf-5, Plt++, Ina−	59
Pf-5 gacA::aphI	JL4577	gacA::aphI derivative of Pf-5; Plt−, Ina−, Kmr	9
Pf-5 pltR::aacCI	JL4563	pltR::aacCI derivative of Pf-5; Plt−, Ina−; Gmr	42
Plasmids
pJEL1703		iceC from P. syringae cloned into pVSP61 (nucleotide sequences of iceC and inaZ are nearly identical)	34
pVSP61		Stable plasmid vector containing pVS1 replicon and mobilization region and p15A replicon; Mob+, Kmr	W. Tucker, DNA Plant Technology Corp., Oakland, Calif.

^aPlt⁺, produces pyoluteorin; Plt⁻, does not produce detectable pyoluteorin; Plt⁺⁺, overproduces pyoluteorin relative to the parental strain; Ina⁺, expresses ice nucleation activity at −5°C; Ina⁻, does not express ice nucleation activity at −5°C; Mob⁺, mobilizable plasmid; Km^r and Gm^r, resistant to kanamycin and gentamycin, respectively.