Construction and screening of PAO1 SALs. (A) Genomic DNA was isolated from P. aeruginosa PAO1 and nebulized to obtain sheared fragments of 200–800 bp. After treatment with exonuclease BAL-31 and Klenow polymerase, the genomic DNA fragments were cloned into the E. coli strain JM109, downstream of the arabinose-inducible promoter PBAD of the pHERD20T vector. (B)E. coli transformants, representing the PAO1 shotgun antisense library (SAL), were arrayed in 96-well microplates and (C) mated with P. aeruginosa PAO1 in the presence of a helper strain (triparental mating). (D) SAL recipient PAO1 exconjugants were selected by spotting on PIA plates supplemented with Cb both in the absence and in the presence of the PBAD inducer arabinose. Recipient PAO1 exconjugant spots were inspected for growth defects following 24 h of incubation at 37°C. (E) The identity of the genomic fragments eliciting growth defects (lethal effects, indicated by a lack of a spot: only with inducer, e.g. clones A4, A8, B5, and E4, and with and without an inducer, e.g. clones A2 and E6; growth impairment, indicated as gray spots: only with an inducer, e.g. clones C2, A6, and B6, and with and without an inducer, e.g. C3 and B8) was determined by sequencing the inserts in the corresponding clones of E. coli SAL.
Rusmini et al. BMC Microbiology 2014 14:24 doi:10.1186/1471-2180-14-24