High frequency FP2 donor of Pseudomonas aeruginosa PAO

Refactoring the Conjugation Machinery of Promiscuous Plasmid RP4 into a Device for Conversion of Gram-Negative Isolates to Hfr Strains

Chromosomal exchange and subsequent recombination of the cognate DNA between bacteria was one of the most useful genetic tools (e.g., Hfr strains) for genetic analyses of E. coli before the genomic era. In this paper, yeast assembly has been used to recruit the conjugation machinery of environmentally promiscuous RP4 plasmid into a minimized, synthetic construct that enables transfer of chromosomal segments between donor/recipient strains of P. putida KT2440 and potentially many other Gram-negative bacteria. The synthetic device features [i] a R6K suicidal plasmid backbone, [ii] a mini-Tn5 transposon vector, and [iii] the minimal set of genes necessary for active conjugation (RP4 Tra1 and Tra2 clusters) loaded as cargo in the mini-Tn5 mobile element. Upon insertion of the transposon in different genomic locations, the ability of P. putida-TRANS (transference of RP4-activated nucleotide segments) donor strains to mobilize genomic stretches of DNA into neighboring bacteria was tested. To this end, a P. putida double mutant ΔpyrF (uracil auxotroph) Δedd (unable to grow on glucose) was used as recipient in mating experiments, and the restoration of the pyrF+/edd+ phenotypes allowed for estimation of chromosomal transfer efficiency. Cells with the inserted transposon behaved in a manner similar to Hfr-like strains and were able to transfer up to 23% of their genome at frequencies close to 10-6 exconjugants per recipient cell. The hereby described TRANS device not only expands the molecular toolbox for P. putida, but it also enables a suite of genomic manipulations which were thus far only possible with domesticated laboratory strains and species.

The Hfr status of Pseudomonas aeruginosa is stabilized by integrative suppression

A temperature-sensitive mutant (dna-11) with the phenotype of a mutant defective in the initiation of DNA replication, was isolated from an Hfr-like FP2 donor of Pseudomonas aeruginosa. Reversion of its temperature-sensitive character was achieved by integrative suppression rather than by backmutation or an additional suppressor mutation. The dna-11 mutant proved to be helpful in stabilizing the Hfr status of the original host.

Transductional analysis of the cysII region of Pseudomonas aeruginosa

The close linkage between hisI and mutations of the cysII group in Pseudomonas aeruginosa was confirmed by mapping experiments with new mutants. All mutants of the cysII group were blocked in the cysteine biosynthesis before sulfite (this include the mutant cys-5605 which had previously been mapped by Mee and Lee, 1969). Most of the sulfite requiring cys mutants belonged to this group. The farthest distance between two mutations of the cysII group was calculated by the Wu formula to be approximately 2.5 kbp. We, therefore, suggest that more than one gene of the cysteine pathway may be located within this region.