Host and invader impact of transfer of the clc genomic island into Pseudomonas aeruginosa PAO1.
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ABSTRACT:
SUBMITTER: Gaillard M
PROVIDER: S-EPMC2383934 | biostudies-literature |
REPOSITORIES: biostudies-literature
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Project description:Pseudomonas aeruginosa is an opportunistic pathogen found ubiquitously in the environment and commonly associated with airway infection in patients with cystic fibrosis. P. aeruginosa strain PAO1 is one of the most commonly used laboratory-adapted research strains and is a standard laboratory-adapted strain in multiple laboratories and strain banks worldwide. Due to potential isolate-to-isolate variability, we investigated the genomic and phenotypic diversity among 10 PAO1 strains (henceforth called sublines) obtained from multiple research laboratories and commercial sources. Genomic analysis predicted a total of 5,682 genes, with 5,434 (95.63%) being identical across all 10 strains. Phenotypic analyses revealed comparable growth phenotypes in rich media and biofilm formation profiles. Limited differences were observed in antibiotic susceptibility profiles and immunostimulatory potential, measured using heat-killed whole-cell preparations in four immortalized cell lines followed by quantification of interleukin-6 (IL-6) and IL-1β secretion. However, variability was observed in the profiles of secreted molecular products, most notably, in rhamnolipid, pyoverdine, pyocyanin, Pseudomonas quinolone signal (PQS), extracellular DNA, exopolysaccharide, and outer membrane vesicle production. Many of the observed phenotypic differences did not correlate with subline-specific genetic changes, suggesting alterations in transcriptional and translational regulation. Taken together, these results suggest that individually maintained sublines of PAO1, even when acquired from the same parent subline, are continuously undergoing microevolution during culture and storage that results in alterations in phenotype, potentially affecting the outcomes of in vitro phenotypic analyses and in vivo pathogenesis studies.IMPORTANCE Laboratory-adapted strains of bacteria are used throughout the world for microbiology research. These prototype strains help keep research data consistent and comparable between laboratories. However, we have observed phenotypic variability when using different strains of Pseudomonas aeruginosa PAO1, one of the major laboratory-adopted research strains. Here, we describe the genomic and phenotypic differences among 10 PAO1 strains acquired from independent sources over 15 years to understand how individual maintenance affects strain characteristics. We observed limited genomic changes but variable phenotypic changes, which may have consequences for cross-comparison of data generated using different PAO1 strains. Our research highlights the importance of limiting practices that may promote the microevolution of model strains and calls for researchers to specify the strain origin to ensure reproducibility.
| S-EPMC6379574 | biostudies-literature
Project description:An unusual type of gene expression from an integrase promoter was found in cultures of the bacterium Pseudomonas sp. strain B13. The promoter controls expression of the intB13 integrase gene, which is present near the right end of a 105-kb conjugative genomic island (the clc element) encoding catabolism of aromatic compounds. The enzymatic activity of integrase IntB13 is essential for site-specific integration of the clc element into the bacterial host's chromosome. By creating transcription fusions between the intB13 promoter and the gfp gene, we showed that integrase expression in strain B13 was inducible under stationary-phase conditions but, strangely, occurred in only a small proportion of individual bacterial cells rather than equally in the whole population. Integrase expression was significantly stimulated by growing cultures on 3-chlorobenzoate. High cell density, heat shock, osmotic shock, UV irradiation, and treatment with alcohol did not result in measurable integrase expression. The occurrence of the excised form of the clc element and an increase in the rates of clc element transfer in conjugation experiments correlated with the observed induction of the intB13'-gfp fusion in stationary phase and in the presence of 3-chlorobenzoate. This suggested that activation of the intB13 promoter is the first step in stimulation of clc transfer. To our knowledge, this is the first report of a chlorinated compound's stimulating horizontal transfer of the genes encoding its very metabolism.
| S-EPMC165761 | biostudies-literature
Project description:Genomic DNA from Pseudomonas aeruginosa strains PAO1 and PA14
2015-11-15 | GSE67038 | GEO
Project description:Pseudomonas sp. strain B13 is a bacterium known to degrade chloroaromatic compounds. The properties to use 3- and 4-chlorocatechol are determined by a self-transferable DNA element, the clc element, which normally resides at two locations in the cell's chromosome. Here we report the complete nucleotide sequence of the clc element, demonstrating the unique catabolic properties while showing its relatedness to genomic islands and integrative and conjugative elements rather than to other known catabolic plasmids. As far as catabolic functions, the clc element harbored, in addition to the genes for chlorocatechol degradation, a complete functional operon for 2-aminophenol degradation and genes for a putative aromatic compound transport protein and for a multicomponent aromatic ring dioxygenase similar to anthranilate hydroxylase. The genes for catabolic functions were inducible under various conditions, suggesting a network of catabolic pathway induction. For about half of the open reading frames (ORFs) on the clc element, no clear functional prediction could be given, although some indications were found for functions that were similar to plasmid conjugation. The region in which these ORFs were situated displayed a high overall conservation of nucleotide sequence and gene order to genomic regions in other recently completed bacterial genomes or to other genomic islands. Most notably, except for two discrete regions, the clc element was almost 100% identical over the whole length to a chromosomal region in Burkholderia xenovorans LB400. This indicates the dynamic evolution of this type of element and the continued transition between elements with a more pathogenic character and those with catabolic properties.
| S-EPMC1426575 | biostudies-literature
Project description:Pseudomonas aeruginosa PAO1 is the most commonly used strain for research on this ubiquitous and metabolically versatile opportunistic pathogen. Strain PAO1, a derivative of the original Australian PAO isolate, has been distributed worldwide to laboratories and strain collections. Over decades discordant phenotypes of PAO1 sublines have emerged. Taking the existing PAO1-UW genome sequence (named after the University of Washington, which led the sequencing project) as a blueprint, the genome sequences of reference strains MPAO1 and PAO1-DSM (stored at the German Collection for Microorganisms and Cell Cultures [DSMZ]) were resolved by physical mapping and deep short read sequencing-by-synthesis. MPAO1 has been the source of near-saturation libraries of transposon insertion mutants, and PAO1-DSM is identical in its SpeI-DpnI restriction map with the original isolate. The major genomic differences of MPAO1 and PAO1-DSM in comparison to PAO1-UW are the lack of a large inversion, a duplication of a mobile 12-kb prophage region carrying a distinct integrase and protein phosphatases or kinases, deletions of 3 to 1,006 bp in size, and at least 39 single-nucleotide substitutions, 17 of which affect protein sequences. The PAO1 sublines differed in their ability to cope with nutrient limitation and their virulence in an acute murine airway infection model. Subline PAO1-DSM outnumbered the two other sublines in late stationary growth phase. In conclusion, P. aeruginosa PAO1 shows an ongoing microevolution of genotype and phenotype that jeopardizes the reproducibility of research. High-throughput genome resequencing will resolve more cases and could become a proper quality control for strain collections.
| S-EPMC2812968 | biostudies-literature
Project description:The large Pseudomonas aeruginosa pathogenicity island PAPI-1 of strain PA14 is a cluster of 108 genes that encode a number of virulence features. We demonstrate that, in a subpopulation of cells, PAPI-1 can exist in an extrachromosomal circular form after precise excision from its integration site within the 3' terminus of the tRNA(Lys) gene. Circular PAPI-1 can reintegrate into either of the two tRNA(Lys) genes, including the one that was used for integration of small pathogenicity island PAPI-2 in strain PA14. The excision requires PAPI-1-encoded integrase, a member of the tyrosine recombinase family. PAPI-1 Soj contains the conserved domains of proteins that are related to chromosome and plasmid partition. soj plays a role in maintaining PAPI-1 and mutations in soj result in the loss of PAPI-1 from P. aeruginosa. We further demonstrate that, during coculture, the PAPI-1-containing strains are able to transfer it into P. aeruginosa recipient strains that do not harbor this island naturally. After transfer, PAPI-1 integrates into either of the two tRNA(Lys) genes. PAPI-1 encompasses many features of mobile elements, including mobilization and maintenance modules. Together with the virulence determinants, PAPI-1 plays an important role in the evolution of P. aeruginosa, by expanding its natural habitat from soil and water to animal and human infections.
| S-EPMC1750864 | biostudies-literature
Project description:Protein glycosylation has been long recognized as an important posttranslational modification process in eukaryotic cells. Glycoproteins, predominantly secreted or surface localized, have also been identified in bacteria. We have identified a cluster of 14 genes, encoding the determinants of the flagellin glycosylation machinery in Pseudomonas aeruginosa PAK, which we called the flagellin glycosylation island. Flagellin glycosylation can be detected only in bacteria expressing the a-type flagellin sequence variants, and the survey of 30 P. aeruginosa isolates revealed coinheritance of the a-type flagellin genes with at least one of the flagellin glycosylation island genes. Expression of the b-type flagellin in PAK, an a-type strain carrying the glycosylation island, did not lead to glycosylation of the b-type flagellin of PAO1, suggesting that flagellins expressed by b-type bacteria not only lack the glycosylation island, they cannot serve as substrates for glycosylation. Providing the entire glycosylation island of PAK, including its a-type flagellin in a flagellin mutant of a b-type strain, results in glycosylation of the heterologous flagellin. These results suggest that some or all of the 14 genes on the glycosylation island are the genes that are missing from strain PAO1 to allow glycosylation of an appropriate flagellin. Inactivation of either one of the two flanking genes present on this island abolished flagellin glycosylation. Based on the limited homologies of these gene products with enzymes involved in glycosylation, we propose that the island encodes similar proteins involved in synthesis, activation, or polymerization of sugars that are necessary for flagellin glycosylation.
| S-EPMC55422 | biostudies-literature
Project description:Pseudomonas aeruginosa is ubiquitously present in the environment and acts as an opportunistic pathogen on humans, animals and plants. We report here the effects of the prebiotic polysaccharide inulin and its hydrolysed form FOS on this bacterium. FOS was found to inhibit bacterial growth of strain PAO1, while inulin did not affect growth rate or yield in a significant manner. Inulin stimulated biofilm formation, whereas a dramatic reduction of the biofilm formation was observed in the presence of FOS. Similar opposing effects were observed for bacterial motility, where FOS inhibited the swarming and twitching behaviour whereas inulin caused its stimulation. In co-cultures with eukaryotic cells (macrophages) FOS and, to a lesser extent, inulin reduced the secretion of the inflammatory cytokines IL-6, IL-10 and TNF-?. Western blot experiments indicated that the effects mediated by FOS in macrophages are associated with a decreased activation of the NF-?B pathway. Since FOS and inulin stimulate pathway activation in the absence of bacteria, the FOS mediated effect is likely to be of indirect nature, such as via a reduction of bacterial virulence. Further, this modulatory effect is observed also with the highly virulent ptxS mutated strain. Co-culture experiments of P. aeruginosa with IEC18 eukaryotic cells showed that FOS reduces the concentration of the major virulence factor, exotoxin A, suggesting that this is a possible mechanism for the reduction of pathogenicity. The potential of these compounds as components of antibacterial and anti-inflammatory cocktails is discussed.
| S-EPMC3899050 | biostudies-literature
Project description:Quorum sensing (QS) is used to coordinate social behaviors, such as virulence and biofilm formation, across bacterial populations. However, the role of QS in regulating phage-bacterium interactions remains unclear. Preventing phage recognition and adsorption are the first steps of bacterial defense against phages; however, both phage recognition and adsorption are a prerequisite for the successful application of phage therapy. In the present study, we report that QS upregulated the expression of phage receptors, thus increasing phage adsorption and infection rates in Pseudomonas aeruginosa. In P. aeruginosa PAO1, we found that las QS, instead of rhl QS, upregulated the expression of galU for lipopolysaccharide synthesis. Lipopolysaccharides act as the receptor of the phage vB_Pae_QDWS. This las QS-mediated phage susceptibility is a dynamic process, depending on host cell density. Our data suggest that inhibiting QS may reduce the therapeutic efficacy of phages. IMPORTANCE Phage resistance is a major limitation of phage therapy, and understanding the mechanisms by which bacteria block phage infection is critical for the successful application of phage therapy. In the present study, we found that Pseudomonas aeruginosa PAO1 uses las QS to promote phage infection by upregulating the expression of galU, which is necessary for the synthesis of phage receptor lipopolysaccharides. In contrast to the results of previous reports, we showed that QS increases the efficacy of phage-mediated bacterial killing. Since QS upregulates the expression of virulence factors and promotes biofilm development, which are positively correlated with lipopolysaccharide production in P. aeruginosa, increased phage susceptibility is a novel QS-mediated trade-off. QS inhibition may increase the efficacy of antibiotic treatment, but it will reduce the effectiveness of phage therapy.
| S-EPMC8764535 | biostudies-literature
Project description:The P. aeruginosa reference strain PAO1 has been used to delineate much of the physiology, metabolism, and fundamental biology of the species. The wild-type parent of PAO1 was lost, and PAO1 carries a regulatory mutation introduced for positive genetic selection that affects antibiotic resistance, virulence, quorum sensing, and other traits. The mutation is a loss-of-function change in an oxidoreductase gene (mexS), which constitutively activates a stress response controlled by a positive regulator (MexT). Fitness defects associated with the constitutive response have led to the inadvertent selection of mexT-minus suppressor mutations, creating genetic heterogeneity in PAO1 sublines studied in different laboratories. To help circumvent complications due to the mexS-minus phenotypes, we created a wild-type version of PAO1 (called LPAO) by "reverting" its mexS to the functional allele likely to have been in its parent. Phenotypic analysis revealed that the mexS-minus allele in PAO1 makes growth sensitive to salt (NaCl) and is lethal when combined with mutations inactivating the major sodium antiporter (ShaABCDEF). The salt sensitivity of PAO1 may underlie some complex mexS-minus phenotypes and help explain the selection of mexT-minus suppressor mutations. To facilitate genetic comparisons of PAO1, LPAO, and other P. aeruginosa strains, we developed a transformation procedure to transfer selectable alleles, such as transposon insertion alleles, between strains. Overall, the study helps explain phenotypic heterogeneity of PAO1-derived strains and provides resources to help recognize and eliminate difficulties due to it. IMPORTANCE The P. aeruginosa reference strain PAO1 carries a regulatory mutation that may affect processes characterized in it. To eliminate complications due to the mutation, we constructed a version of the missing wild-type parent strain and developed methods to transfer mutations between PAO1 and the new strain. The methods are likely to be applicable to other isolates of P. aeruginosa as well.
| S-EPMC8223932 | biostudies-literature