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The American Naturalist Jul 2010Dispersal plays a crucial role in a range of evolutionary and ecological processes; hence there is strong motivation to understand its evolution. One key prediction is...
Dispersal plays a crucial role in a range of evolutionary and ecological processes; hence there is strong motivation to understand its evolution. One key prediction is that the relative benefits of dispersal should be greater when dispersing away from close relatives, because in this case dispersal has the additional benefit of alleviating competition with individuals who share the same dispersal alleles. We tested this prediction for the first time using experimental populations of the opportunistic pathogen Pseudomonas aeruginosa. We measured the fitness of isogenic genotypes that differed only in their dispersal behaviors in both clonal and mixed populations. Consistent with theory, the benefit of dispersal was much higher in clonal populations, and this benefit decreased with increasing growth rate costs associated with dispersal.
Topics: Biological Evolution; Demography; Genetic Fitness; Population Density; Population Dynamics; Pseudomonas aeruginosa; Virulence
PubMed: 20500040
DOI: 10.1086/652995 -
Journal of Medical Microbiology Jan 2020Laboratory research with commonly involves the prototype strain PAO1. There is continued concern that PAO1 sublines maintained and propagated in the same laboratory or...
Laboratory research with commonly involves the prototype strain PAO1. There is continued concern that PAO1 sublines maintained and propagated in the same laboratory or different laboratories exhibit genetic and phenotypic variability that may affect the reproducibility and validity of research. Whole-genome sequencing and other research identified the locus as a mutational hotspot, but the explication of the diverse mutations present in the various sublines and consequences remained rather cursory. Here we present evidence that MexT sequence diversity is a predictor of PAO1 lineage integrity and define the protein's prototype sequence.
Topics: Bacterial Proteins; Genetic Variation; Mutation; Pseudomonas aeruginosa; Serial Passage; Whole Genome Sequencing
PubMed: 31859619
DOI: 10.1099/jmm.0.001128 -
Microbial Biotechnology Jan 2009Indole is an extracellular biofilm signal for Escherichia coli, and many bacterial oxygenases readily convert indole to various oxidized compounds including...
Indole is an extracellular biofilm signal for Escherichia coli, and many bacterial oxygenases readily convert indole to various oxidized compounds including 7-hydroxyindole (7HI). Here we investigate the impact of indole and 7HI on Pseudomonas aeruginosa PAO1 virulence and quorum sensing (QS)-regulated phenotypes; this strain does not synthesize these compounds but degrades them rapidly. Indole and 7HI both altered extensively gene expression in a manner opposite that of acylhomoserine lactones; the most repressed genes encode the mexGHI-opmD multidrug efflux pump and genes involved in the synthesis of QS-regulated virulence factors including pyocyanin (phz operon), 2-heptyl-3-hydroxy-4(1H)-quinolone (PQS) signal (pqs operon), pyochelin (pch operon) and pyoverdine (pvd operon). Corroborating these microarray results, indole and 7HI decreased production of pyocyanin, rhamnolipid, PQS and pyoverdine and enhanced antibiotic resistance. In addition, indole affected the utilization of carbon, nitrogen and phosphorus, and 7HI abolished swarming motility. Furthermore, 7HI reduced pulmonary colonization of P. aeruginosa in guinea pigs and increased clearance in lungs. Hence, indole-related compounds have potential as a novel antivirulence approach for the recalcitrant pathogen P. aeruginosa.
Topics: Animals; Bacterial Proteins; Down-Regulation; Gene Expression Regulation, Bacterial; Guinea Pigs; Humans; Indoles; Lung; Pseudomonas Infections; Pseudomonas aeruginosa; Quorum Sensing; Virulence
PubMed: 21261883
DOI: 10.1111/j.1751-7915.2008.00061.x -
PloS One 2013Pseudomonas aeruginosa is an opportunistic pathogen that can cause a wide range of infections and inflammations in a variety of hosts, such as chronic biofilm associated...
Pseudomonas aeruginosa is an opportunistic pathogen that can cause a wide range of infections and inflammations in a variety of hosts, such as chronic biofilm associated lung infections in Cystic Fibrosis patients. Phosphate, an essential nutrient, has been recognized as an important signal that affects virulence in P. aeruginosa. In the current study we examined the connection between phosphate regulation and surface motility in P. aeruginosa. We focused on two important genes, pstS, which is involved in phosphate uptake, and phoB, a central regulator that responds to phosphate starvation. We found that a mutant lacking pstS is constantly starved for phosphate and has a hyper swarming phenotype. Phosphate starvation also induced swarming in the wild type. The phoB mutant, on the other hand, did not express phosphate starvation even when phosphate was limited and showed no swarming. A double mutant lacking both genes (pstS and phoB) showed a similar phenotype to the phoB mutant (i.e. no swarming). This highlights the role of phoB in controlling swarming motility under phosphate-depleted conditions. Finally, we were able to demonstrate that PhoB controls swarming by up-regulating the Rhl quorum sensing system in P. aeruginosa, which resulted in hyper production of rhamonlipids: biosurfactants that are known to induce swarming motility.
Topics: Bacterial Proteins; Glycolipids; Movement; Mutation; Phosphates; Pseudomonas aeruginosa; Quorum Sensing
PubMed: 24023943
DOI: 10.1371/journal.pone.0074444 -
Antimicrobial Agents and Chemotherapy Jul 2011Azithromycin at clinically relevant doses does not inhibit planktonic growth of the opportunistic pathogen Pseudomonas aeruginosa but causes markedly reduced formation...
Azithromycin at clinically relevant doses does not inhibit planktonic growth of the opportunistic pathogen Pseudomonas aeruginosa but causes markedly reduced formation of biofilms and quorum-sensing-regulated extracellular virulence factors. In the Gac/Rsm signal transduction pathway, which acts upstream of the quorum-sensing machinery in P. aeruginosa, the GacA-dependent untranslated small RNAs RsmY and RsmZ are key regulatory elements. As azithromycin treatment and mutational inactivation of gacA have strikingly similar phenotypic consequences, the effect of azithromycin on rsmY and rsmZ expression was investigated. In planktonically growing cells, the antibiotic strongly inhibited the expression of both small RNA genes but did not affect the expression of the housekeeping gene proC. The azithromycin treatment resulted in reduced expression of gacA and rsmA, which are known positive regulators of rsmY and rsmZ, and of the PA0588-PA0584 gene cluster, which was discovered as a novel positive regulatory element involved in rsmY and rsmZ expression. Deletion of this cluster resulted in diminished ability of P. aeruginosa to produce pyocyanin and to swarm. The results of this study indicate that azithromycin inhibits rsmY and rsmZ transcription indirectly by lowering the expression of positive regulators of these small RNA genes.
Topics: Anti-Bacterial Agents; Azithromycin; Bacterial Proteins; Blotting, Northern; Gene Expression Regulation, Bacterial; Pseudomonas aeruginosa
PubMed: 21537014
DOI: 10.1128/AAC.01801-10 -
Antimicrobial Agents and Chemotherapy May 2018Segregation of bacteria based on their metabolic activities in biofilms plays an important role in the development of antibiotic resistance. Mushroom-shaped biofilm...
Segregation of bacteria based on their metabolic activities in biofilms plays an important role in the development of antibiotic resistance. Mushroom-shaped biofilm structures, which are reported for many bacteria, exhibit topographically varying levels of multiple drug resistance from the cap of the mushroom to its stalk. Understanding the dynamics behind the formation of such structures can aid in design of drug delivery systems, antibiotics, or physical systems for removal of biofilms. We explored the development of metabolically heterogeneous biofilms using numerical models and laboratory knockout experiments on wild-type and chemotaxis-deficient mutants. We show that chemotactic processes dominate the transformation of slender and hemispherical structures into mushroom structures with a signature cap. Cellular Potts model simulation and experimental data provide evidence that accelerated movement of bacteria along the periphery of the biofilm, due to nutrient cues, results in the formation of mushroom structures and bacterial segregation. Multidrug resistance of bacteria is one of the most threatening dangers to public health. Understanding the mechanisms of the development of mushroom-shaped biofilms helps to identify the multidrug-resistant regions. We decoded the dynamics of the structural evolution of bacterial biofilms and the physics behind the formation of biofilm structures as well as the biological triggers that produce them. Combining gene knockout experiments with models showed that chemotactic motility is one of the main driving forces for the formation of stalks and caps. Our results provide physicists and biologists with a new perspective on biofilm removal and eradication strategies.
Topics: Anti-Bacterial Agents; Biofilms; Pseudomonas aeruginosa
PubMed: 29463543
DOI: 10.1128/AAC.02544-17 -
Genome Biology and Evolution Jul 2018Pseudomonas aeruginosa is an important opportunistic pathogen in hospitals, responsible for various infections that are difficult to treat due to intrinsic and acquired...
Pseudomonas aeruginosa is an important opportunistic pathogen in hospitals, responsible for various infections that are difficult to treat due to intrinsic and acquired antibiotic resistance. Here, 20 epidemiologically unrelated strains isolated from patients in a general hospital over a time period of two decades were analyzed using whole genome sequencing. The genomes were compared in order to assess the presence of a predominant clone or sequence type (ST). No clonal structure was identified, but core genome-based single nucleotide polymorphism (SNP) analysis distinguished two major, previously identified phylogenetic groups. Interestingly, most of the older strains isolated between 1994 and 1998 harbored exoU, encoding a cytotoxic phospholipase. In contrast, most strains isolated between 2011 and 2016 were exoU-negative and phylogenetically very distinct from the older strains, suggesting a population shift of nosocomial P. aeruginosa over time. Three out of 20 strains were ST235 strains, a global high-risk clonal lineage; these carried several additional resistance determinants including aac(6')Ib-cr encoding an aminoglycoside N-acetyltransferase that confers resistance to fluoroquinolones. Core genome comparison with ST235 strains from other parts of the world showed that the three strains clustered together with other Brazilian/Argentinean isolates. Despite this regional relatedness, the individuality of each of the three ST235 strains was revealed by core genome-based SNPs and the presence of genomic islands in the accessory genome. Similarly, strain-specific characteristics were detected for the remaining strains, indicative of individual evolutionary histories and elevated genome plasticity.
Topics: Brazil; Genome, Bacterial; Humans; Phylogeny; Pseudomonas Infections; Pseudomonas aeruginosa; Sequence Analysis, DNA
PubMed: 29982603
DOI: 10.1093/gbe/evy139 -
BMC Microbiology Aug 2018Pseudomonas aeruginosa is an opportunistic bacterial pathogen responsible for both acute and chronic infections in humans. In particular, its ability to form biofilm, on...
BACKGROUND
Pseudomonas aeruginosa is an opportunistic bacterial pathogen responsible for both acute and chronic infections in humans. In particular, its ability to form biofilm, on biotic and abiotic surfaces, makes it particularly resistant to host's immune defenses and current antibiotic therapies as well. Innovative antimicrobial materials, like hydrogel, silver salts or nanoparticles have been used to cover new generation catheters with promising results. Nevertheless, biofilm remains a major health problem. For instance, biofilm produced onto endotracheal tubes (ETT) of ventilated patients plays a relevant role in the onset of ventilation-associated pneumonia. Most of our knowledge on Pseudomonas aeruginosa biofilm derives from in vitro studies carried out on abiotic surfaces, such as polystyrene microplates or plastic materials used for ETT manufacturing. However, these approaches often provide underestimated results since other parameters, in addition to bacterial features (i.e. shape and material composition of ETT) might strongly influence biofilm formation.
RESULTS
We used an already established biofilm development assay on medically-relevant foreign devices (CVC catheters) by a stably transformed bioluminescent (BLI)-Pseudomonas aeruginosa strain, in order to follow up biofilm formation on ETT by bioluminescence detection. Our results demonstrated that it is possible: i) to monitor BLI-Pseudomonas aeruginosa biofilm development on ETT pieces in real-time, ii) to evaluate the three-dimensional structure of biofilm directly on ETT, iii) to assess metabolic behavior and the production of microbial virulence traits of bacteria embedded on ETT-biofilm.
CONCLUSIONS
Overall, we were able to standardize a rapid and easy-to-perform in vitro model for real-time monitoring Pseudomonas aeruginosa biofilm formation directly onto ETT pieces, taking into account not only microbial factors, but also ETT shape and material. Our study provides a rapid method for future screening and validation of novel antimicrobial drugs as well as for the evaluation of novel biomaterials employed in the production of new classes of ETT.
Topics: Anti-Infective Agents; Biofilms; Catheters; Equipment Contamination; In Vitro Techniques; Intubation, Intratracheal; Pseudomonas aeruginosa; Time Factors; Virulence
PubMed: 30107778
DOI: 10.1186/s12866-018-1224-6 -
PloS One 2011The importance of rhamnolipid to swarming of the bacterium Pseudomonas aeruginosa is well established. It is frequently, but not exclusively, observed that P. aeruginosa...
The importance of rhamnolipid to swarming of the bacterium Pseudomonas aeruginosa is well established. It is frequently, but not exclusively, observed that P. aeruginosa swarms in tendril patterns--formation of these tendrils requires rhamnolipid. We were interested to explain the impact of surface changes on P. aeruginosa swarm tendril development. Here we report that P. aeruginosa quorum sensing and rhamnolipid production is impaired when growing on harder semi-solid surfaces. P. aeruginosa wild-type swarms showed huge variation in tendril formation with small deviations to the "standard" swarm agar concentration of 0.5%. These macroscopic differences correlated with microscopic investigation of cells close to the advancing swarm edge using fluorescent gene reporters. Tendril swarms showed significant rhlA-gfp reporter expression right up to the advancing edge of swarming cells while swarms without tendrils (grown on harder agar) showed no rhlA-gfp reporter expression near the advancing edge. This difference in rhamnolipid gene expression can be explained by the necessity of quorum sensing for rhamnolipid production. We provide evidence that harder surfaces seem to limit induction of quorum sensing genes near the advancing swarm edge and these localized effects were sufficient to explain the lack of tendril formation on hard agar. We were unable to artificially stimulate rhamnolipid tendril formation with added acyl-homoserine lactone signals or increasing the carbon nutrients. This suggests that quorum sensing on surfaces is controlled in a manner that is not solely population dependent.
Topics: Acyl-Butyrolactones; Agar; Gene Expression Regulation, Bacterial; Glycolipids; Hardness; Phenotype; Pseudomonas aeruginosa; Quorum Sensing; Surface Properties
PubMed: 21687741
DOI: 10.1371/journal.pone.0020888 -
Journal of Bacteriology Feb 2019Dimethyl sulfide (DMS) is a volatile sulfur compound produced mainly from the degradation of dimethylsulfoniopropionate (DMSP) in marine environments. DMS undergoes...
Dimethyl sulfide (DMS) is a volatile sulfur compound produced mainly from the degradation of dimethylsulfoniopropionate (DMSP) in marine environments. DMS undergoes oxidation to form dimethyl sulfoxide (DMSO), dimethyl sulfone (DMSO), and methanesulfonate (MSA), all of which occur in terrestrial environments and are accessible for consumption by various microorganisms. The purpose of the present study was to determine how the enhancer-binding proteins SfnR1 and SfnR2 contribute to the utilization of DMS and its derivatives in PAO1. First, results from cell growth experiments showed that deletion of either or , a gene encoding a DMSO-monooxygenase, significantly inhibits the ability of PAO1 to use DMSP, DMS, DMSO, and DMSO as sulfur sources. Deletion of the or genes, which encode a MSA desulfurization pathway, did not abolish the growth of PAO1 on any sulfur compound tested. Second, data collected from β-galactosidase assays revealed that the operon and the gene are induced in response to sulfur limitation or nonpreferred sulfur sources, such as DMSP, DMS, and DMSO, etc. Importantly, SfnR2 (and not SfnR1) is essential for this induction. Expression of is induced under sulfur limitation but independently of SfnR1 or SfnR2. Finally, the results of this study suggest that the main function of SfnR2 is to direct the initial activation of the operon in response to sulfur limitation or nonpreferred sulfur sources. Once expressed, SfnR1 contributes to the expression of , , and other target genes involved in DMS-related metabolism in PAO1. Dimethyl sulfide (DMS) is an important environmental source of sulfur, carbon, and/or energy for microorganisms. For various bacteria, including , , and , DMS utilization is thought to be controlled by the transcriptional regulator SfnR. Adding more complexity, some bacteria, such as , , and , possess two, nonidentical SfnR proteins. In this study, we demonstrate that SfnR2 and not SfnR1 is the principal regulator of DMS metabolism in PAO1. Results suggest that SfnR1 has a supportive but nonessential role in the positive regulation of genes required for DMS utilization. This study not only enhances our understanding of SfnR regulation but, importantly, also provides a framework for addressing gene regulation through dual SfnR proteins in other bacteria.
Topics: Gene Deletion; Gene Expression Regulation, Bacterial; Protein Binding; Pseudomonas aeruginosa; Sulfides; Transcription Factors
PubMed: 30478084
DOI: 10.1128/JB.00606-18