Aliquots (5 μL) of the PCR products were analyzed by electrophoresis in 1% agarose gels, stained with ethidium bromide and photographed under UV illumination. Cloning and sequencing the hrcRST PCR fragment PCR products were cloned with the pMOSBlue blunt-ended cloning kit (Amersham/Biosciences). MOS cells Selleck NVP-BEZ235 were transformed and, after blue/white colony screening, clones were picked and plasmid DNA was isolated with the QIAprep Spin Miniprep Kit (Qiagen). The PCR products were sequenced by Genome Express (France). The predicted sequences of MFN1032 hrcRST and MF37 hrcRST were submitted for BLAST queries http://​www.​ncbi.​nlm.​nih.​gov/​BLAST/​.

Construction of MFN1030, an hrcU operon-disrupted mutant of MFN1032 and MF1031, its revertant The hrcRST-pMOS SIS3 price plasmid from

MFN1032 was digested with EcoRI/HindIII and subsequently hrcRST fragment was inserted into the transferable suicide plasmid pME3087 (6,9 Kb) digested by the same enzymes [44]. This construction, pME3087-hrcRST (7,8 kb), was then introduced into Escherichia coli DH5α MCR cells by electroporation. Plasmids were isolated using the QIAprep Spin Miniprep Kit (Qiagen), checked by digestion with HindIII/EcoRI and transferred into the Escherichia coli conjugative strain S17.1 [45]. Colonies were selected for their resistance to tetracycline (20 μg/mL). MFN1032 (naturally ampicillin resistant) cells were conjugated with S17.1 cells carrying the pME3087-hrcRST plasmid and strains were selected for their resistance to tetracycline (20 μg/mL) and ampicillin (100 μg/mL) that corresponds to insertion of the whole plasmid via a single homologue recombinaison. RNA Synthesis inhibitor One of the clones was selected and corresponded to an hrpU operon disruption mutant.

This disruption mutant was called MFN1030. The reversion of the mutant MFN1030 was obtained after incubating MFN1030 cells on an LB agar plate for 72 hours. Of all the colonies obtained, 100 were PR-171 in vitro subcultured in parallel on LB agar plates with or without tetracycline (20 μg/mL). Colonies growing on LB agar plates without tetracycline but not on LB agar plates with tetracycline (20 μg/mL) reflect a second recombination event and an excision of the plasmid. One clone was selected and named MFN1031, a revertant of MFN1030 strain. Acknowledgements The Région Haute-Normandie supported this work. We thank Magalie Barreau for technical help. References 1. Couillerot O, Prigent-Combaret C, Caballero-Mellado J, Moenne-Loccoz Y: Pseudomonas fluorescens and closely-related fluorescent pseudomonads as biocontrol agents of soil-borne phytopathogens. Lett Appl Microbiol 2009,48(5):505–512.PubMedCrossRef 2. Tourkya B, Boubellouta T, Dufour E, Leriche F: Fluorescence spectroscopy as a promising tool for a polyphasic approach to pseudomonad taxonomy. Curr Microbiol 2009,58(1):39–46.PubMedCrossRef 3.