TABLE 1.

Bacterial strains and plasmids used in this study

Strains or plasmid	Relevant characteristicsa	Reference or Source
P. fluorescens
WCS365	Wild-type biocontrol strain; efficient competitive colonizer of tomato, potato, and wheat roots; Nalr	5, 30
PCL1285	Kmr derivative of WCS365 not impaired in competitive root colonization on tomato and grass; Kmr	This study
PCL1286	WCS365 Tn5luxAB mutant with an impaired mutY gene and enhanced competitive colonizing abilities on tomato and grass; Kmr	This study
PCL1805	WCS365 mutant with an impaired mutY gene obtained by single homologous recombination; impaired in competitive colonizing abilities on tomato and grass; Kmr	This study
PCL1808	WCS365 mutant with an impaired mutY gene obtained by single homologous recombination (PCL 1805) and 3 cycles of enrichment on tomato; enhanced in competitive colonization on tomato and grass; Kmr	This study
WCS365(3X)	WCS365 variant obtained after 3 enrichment cycles on tomato; wild-type colonizing abilities	This study
PCL1285(3X)	PCL1285 variant obtained after 3 enrichment cycles on tomato; wild-type colonizing abilities	This study
PCL1814	PCL1286 variant harboring pMP5573; Kmr Tcr	This study
PCL1815	PCL1805 variant harboring pMP5573; Kmr Tcr	This study
PCL1816	PCL1808 variant harboring pMP5573; Kmr Tcr	This study
PCL1817	WCS365 variant harboring pMP5573; Tcr	This study
E. coli
XL1-Blue	Used for transformation and propagation of plasmids	Stratagene, La Jolla, Calif.
DH5α	Used for transformation and propagation of plasmids	10
Plasmids
pRL1063A	Plasmid harboring promoterless Tn5luxAB; Kmr	41
pRK2013	Helper plasmid for triparental mating; Nmr Kmr	8
pGEM-T-easy	Cloning vector for Taq-amplified PCR products; Apr	Promega
pMP4655	pME6010 derivative expressing egfp under the control of the lac promoter; Tcr	2
pMP4662	pME6010 derivative expressing rfp under the control of the lac promoter; Tcr	2
pMP5285	pME3049 (38) derivative; suicide plasmid for Pseudomonas spp.; used for homologous recombination; Kmr Cbr	15
pMP5421	pRL1063A derivative recovered from chromosomal DNA of PCL1286 after digestion with EcoRI; Kmr	This study
pMP5465	pGEM-T Easy containing 1,187-bp PCR fragment of mutY; Apr	This study
pMP5564	pMP5285 harboring part of PCR fragment of mutY from pMP5465 used for homologous recombination; Kmr	This study
pMP5572	pGEM-T Easy containing 1,742-bp PCR fragment including complete mutY gene; Apr	This study
pME6031	Stable shuttle vector for gram-negative bacteria based on pVS1 replicon (34), contains extra transcriptional terminator; Tcr	11
pMP5573	pME6031 derivative containing complete mutY gene, used for complementation; Tcr	This study

^aResistance phenotypes; Ap^r, ampicillin; Nal^r, nalidixic acid; Cb^r, carbenicillin; Nm^r, neomycin; Km^r, kanamycin; Tc^r, tetracycline.