Methods for genetic manipulation of Burkholderia gladioli pathovar cocovenenans

<p>Abstract</p> <p>Background</p> <p><it>Burkholderia gladioli </it>pathovar <it>cocovenenans </it>(BGC) is responsible for sporadic food-poisoning outbreaks with high morbidity and mortality in Asian countries. Little is known about the regulation of virulence factor and toxin production in BGC, and studies in this bacterium have been hampered by lack of genetic tools.</p> <p>Findings</p> <p>Establishment of a comprehensive antibiotic susceptibility profile showed that BGC strain ATCC33664 is susceptible to a number of antibiotics including aminoglycosides, carbapenems, fluoroquinolones, tetracyclines and trimethoprim. In this study, we established that gentamicin, kanamycin and trimethoprim are good selection markers for use in BGC. Using a 10 min method for preparation of electrocompetent cells, the bacterium could be transformed by electroporation at high frequencies with replicative plasmids containing the pRO1600-derived origin of replication. These plasmids exhibited a copy number of > 100 in BGC. When co-conjugated with a transposase expressing helper plasmid, mini-Tn<it>7 </it>vectors inserted site- and orientation-specifically at a single <it>glmS</it>-associated insertion site in the BGC genome. Lastly, a <it>Himar1 </it>transposon was used for random transposon mutagenesis of BGC.</p> <p>Conclusions</p> <p>A series of genetic tools previously developed for other Gram-negative bacteria was adapted for use in BGC. These tools now facilitate genetic studies of this pathogen and allow establishment of toxin biosynthetic pathways and their genetic regulation.</p

Creation of an endA mutant strain in Pseudomonas aeruginosa PAO1 using gene replacement

Endonuclease I is an enzyme encoded by the endA gene. This nuclease degrades double stranded DNA. Many Escherichia coli common laboratory strains contain a mutation in the endA gene that inactivates the DNA-specific endonuclease I. A mutation in this gene greatly increases plasmid DNA yields in such E. coli strains as well as improves the quality of DNA that is isolated. The purpose of this research is to create an endA mutant strain in Pseudomonas aeruginosa PAO1 using gene replacement, thereby leading to the development of a useful laboratory Pseudomonas strain for use as a cloning strain. To accomplish this, chromosomal DNA from P. aeruginosa PAO1 was isolated, and the endA gene was then amplified by PCR using specific primers designed to the flanking upstream and downstream sequence of the endA coding region. The resulting amplified 1100 bp DNA fragment containing the endA gene was cloned into pCR2.1. This newly created plasmid was named pCR2.1-endA. In order to create an insertionally inactivated endA gene, a GmR encoding cassette from pPS856 needed to be inserted into the SalI sites of the cloned endA gene. The pCR2.1-endA plasmid was digested using SalI restriction enzyme. A 4500 bp SalI fragment of pCR2.1-endA was isolated and then religated by T4 DNA ligase. The new plasmid created was called pCR2.1-endASalID. This plasmid was digested with SalI, and blunt ends were created with T4 DNA polymerase. Inactivation of the endA gene was accomplished by insertion of a blunt-ended, GmR encoding gene into the blunt-ended SalI site of the endA coding sequence. The resulting recombinant plasmid was called pCR2.1-endASalID(Gm1). A 1700 bp HindIII x PstI DNA fragment from pCR2.1-endASalID(Gm1), containing the insertionally inactivated endA gene, was isolated and cloned into the similarly digested pEX18Ap plasmid.High Honors