Abstract
BackgroundPseudomonas aeruginosa is a cause of nosocomial infections, especially in patients with cystic fibrosis and burn wounds. PAO1 strain and its derivatives are widely used to study the biology of this bacterium, however recent studies demonstrated differences in the genomes and phenotypes of derivatives from different laboratories.ResultsHere we report the genome sequence of P. aeruginosa PAO1161 laboratory strain, a leu-, RifR, restriction-modification defective PAO1 derivative, described as the host of IncP-8 plasmid FP2, conferring the resistance to mercury. Comparison of PAO1161 genome with PAO1-UW sequence revealed lack of an inversion of a large genome segment between rRNA operons and 100 nucleotide polymorphisms, short insertions and deletions. These included a change in leuA, resulting in E108K substitution, which caused leucine auxotrophy and a mutation in rpoB, likely responsible for the rifampicin resistance. Nonsense mutations were detected in PA2735 and PA1939 encoding a DNA methyltransferase and a putative OLD family endonuclease, respectively. Analysis of revertants in these two genes showed that PA2735 is a component of a restriction-modification system, independent of PA1939. Moreover, a 12 kb RPG42 prophage and a novel 108 kb PAPI-1 like integrative conjugative element (ICE) encompassing a mercury resistance operon were identified. The ICEPae1161 was transferred to Pseudomonas putida cells, where it integrated in the genome and conferred the mercury resistance.ConclusionsThe high-quality P. aeruginosa PAO1161 genome sequence provides a reference for further research including e.g. investigation of horizontal gene transfer or comparative genomics.The strain was found to carry ICEPae1161, a functional PAPI-1 family integrative conjugative element, containing loci conferring mercury resistance, in the past attributed to the FP2 plasmid of IncP-8 incompatibility group. This indicates that the only known member of IncP-8 is in fact an ICE.
Highlights
Pseudomonas aeruginosa is a cause of nosocomial infections, especially in patients with cystic fibrosis and burn wounds
Recent analyses indicated that sequence variation including singlenucleotide polymorphisms (SNPs), multiple-nucleotide polymorphisms (MNPs) and indels could lead to major variations in e.g. virulence and fitness between strains used in different laboratories [7]
A phylogenetic comparison of PAO1161 genome with other P. aeruginosa genomes available in the National Center for Biotechnology Information (NCBI) database, identified C7447m, a mucoid isolate from a patient with cystic fibrosis [34] as a strain with most similar genome
Summary
Pseudomonas aeruginosa is a cause of nosocomial infections, especially in patients with cystic fibrosis and burn wounds. Comparison of PAO1161 genome with PAO1-UW sequence revealed lack of an inversion of a large genome segment between rRNA operons and 100 nucleotide polymorphisms, short insertions and deletions These included a change in leuA, resulting in E108K substitution, which caused leucine auxotrophy and a mutation in rpoB, likely responsible for the rifampicin resistance. Recent analyses indicated that sequence variation including singlenucleotide polymorphisms (SNPs), multiple-nucleotide polymorphisms (MNPs) and indels could lead to major variations in e.g. virulence and fitness between strains used in different laboratories [7] This indicates an ongoing micro- and macro- evolution of bacterial genomes and suggests that sequence diversification in laboratory strains should be taken into consideration in the analysis of phenotypic data [9,10,11,12]
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