The inserts were sequenced by dye terminator cycle sequencing (DNA Sequencing Facility, College of Biological Sciences,

University of Guelph, Guelph, ON) and compared with the annotated genome sequences of A. pleuropneumoniae using Blastx available at http://​blast.​ncbi.​nlm.​nih.​gov/​Blast.​cgi to identify the complete genes. Construction of the malT knockout mutant Based on the genome sequence of A. pleuropneumoniae serovar 1 strain 4074, primers were designed to amplify the www.selleckchem.com/products/BI-2536.html entire malT gene (nucleotides 2118860 to 2121577). The malT PCR product was purified and cloned into pCR4-TOPO. The resultant plasmid was used as the template in a PCR reaction to produce a linearized plasmid with a deletion of the central 838 bp (bp 922 to bp 1760) of the malT gene. The amplicon was generated using Phusion Taq DNA

polymerase (New England Biolabs), a high fidelity DNA polymerase, and the primers that annealed in back to back manner leaving a central 900 bp region of the plasmid malT between them. Following the gel purification of the PCR product, the omlA-P promoter see more driven chloramphenicol acetyl transferase gene (cat), obtained by PCR amplification of pEMOC2 [34] was blunt-end ligated with the linear plasmid. The resultant circular plasmid with the cat insertion in the malT was designated as pTopoMC. The ΔmalT::cat fragment of pTopoMC was then PCR amplified find more with forward and reverse primers containing NotI and PstI sites, respectively. The ΔmalT::cat PCR amplicon was gel purified, digested with NotI and PstI, and cloned into pEMOC2. The resultant plasmid, named pEMOC2M, was electroporated into E. coli β2155. pEMOC2M was mobilized from E. coli β2155 into

A. pleuropneumoniae CM5 using a modification of the filter mating technique described by Oswald et al. [35]. Briefly, overnight cultures of E. coli β2155/pEMOC2M (grown on LB agar containing 25 μg/ml chloramphenicol), and A. pleuropneumoniae CM5 (grown on BHI agar) were washed with 2 ml of TNM buffer (1 mM Tris-HCl, pH 7.2; 10 mM MgSO4; 100 mM NaCl). The OD600 of both the donor and the recipient strains was adjusted to 1 by adding TNM buffer. A 100 μl volume of the donor and very 10 μl of the recipient strains were mixed by inversion, and the mixture was centrifuged to pellet the cells, which were washed and then resuspended in 1 ml of fresh TNM buffer. A 50 μl volume of the suspension was spotted onto a 0.45 μm nitrocellulose filter (Pall Corporation) placed onto the BHI agar plate containing DAP and MgSO4 (10 mM). After incubation at 37°C for 6 h in an atmosphere of 5% CO2, the filter was washed with 5 ml of BHI broth. The cells were harvested by centrifugation and re-suspended in 0.5 ml of BHI broth. After 10-fold serial dilution of the cell suspension, 50 μl of cells from each of the dilution was plated onto BHI agar plates containing chloramphenicol (5 μg/ml).