Cation complexation by mucoid Pseudomonas aeruginosa extracellular polysaccharide.
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ABSTRACT:
SUBMITTER: Hills OJ
PROVIDER: S-EPMC8412252 | biostudies-literature |
REPOSITORIES: biostudies-literature
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Project description:Pseudomonas aeruginosa is one of the most common biofilm-forming pathogens responsible for lung infections of individuals with cystic fibrosis (CF). P. aeruginosa becomes tolerant to antimicrobials in the biofilm state and is difficult to treat. Production of extracellular polymeric substances (EPS), such as alginate and extracellular DNA (eDNA), can allow adherence to abiotic and biotic surfaces, antimicrobial evasion, and resilience to environmental pressures. Alginate-producing mucoid variants of P. aeruginosa are frequently isolated from CF airway samples and are associated with worsening patient outcomes. While eDNA is a major structural component of nonmucoid P. aeruginosa biofilms, the potential role of eDNA in mucoid biofilms is unclear. Here, we investigate how eDNA contributes to clinical mucoid biofilm physiology and integrity. We predicted that eDNA plays a structural and mechanical role in mucoid biofilms. To test this, we quantified biofilm eDNA in mucoid biofilms and used microscopy and rheology to visualize eDNA and detect changes in biofilm structure and mechanics upon DNaseI treatment. We showed that biofilm eDNA abundance is diverse across clinical mucoid strains and observed a temporal increase in foci of eDNA within intact mucoid biofilms. Increased cell dispersal and reduced biomass were also observed following DNaseI treatment of mucoid biofilms. Degradation of eDNA also impacted the mechanical integrity of mucoid biofilms by increasing the stiffness and decreasing the cohesion of the biofilm. These findings advance our understanding of clinical mucoid P. aeruginosa biofilms and facilitate the development of new approaches to target biofilms by exploiting the functions of EPS components. IMPORTANCE Understanding the role of eDNA in mucoid Pseudomonas aeruginosa biofilms will lead to therapeutic strategies that combat the biophysical and structural function of EPS for the eradication of bacteria in mucoid biofilms during chronic infections. This knowledge can be used to further identify unknown matrix component interactions within pathogenic biofilm-forming clinical isolates.
| S-EPMC10601617 | biostudies-literature
Project description:UnlabelledAdaptation of bacterial pathogens to a host can lead to the selection and accumulation of specific mutations in their genomes with profound effects on the overall physiology and virulence of the organisms. The opportunistic pathogen Pseudomonas aeruginosa is capable of colonizing the respiratory tract of individuals with cystic fibrosis (CF), where it undergoes evolution to optimize survival as a persistent chronic human colonizer. The transcriptome of a host-adapted, alginate-overproducing isolate from a CF patient was determined following growth of the bacteria in the presence of human respiratory mucus. This stable mucoid strain responded to a number of regulatory inputs from the mucus, resulting in an unexpected repression of alginate production. Mucus in the medium also induced the production of catalases and additional peroxide-detoxifying enzymes and caused reorganization of pathways of energy generation. A specific antibacterial type VI secretion system was also induced in mucus-grown cells. Finally, a group of small regulatory RNAs was identified and a fraction of these were mucus regulated. This report provides a snapshot of responses in a pathogen adapted to a human host through assimilation of regulatory signals from tissues, optimizing its long-term survival potential.ImportanceThe basis for chronic colonization of patients with cystic fibrosis (CF) by the opportunistic pathogen Pseudomonas aeruginosa continues to represent a challenging problem for basic scientists and clinicians. In this study, the host-adapted, alginate-overproducing Pseudomonas aeruginosa 2192 strain was used to assess the changes in its transcript levels following growth in respiratory CF mucus. Several significant and unexpected discoveries were made: (i) although the alginate overproduction in strain 2192 was caused by a stable mutation, a mucus-derived signal caused reduction in the transcript levels of alginate biosynthetic genes; (ii) mucus activated the expression of the type VI secretion system, a mechanism for killing of other bacteria in a mixed population; (iii) expression of a number of genes involved in respiration was altered; and (iv) several small regulatory RNAs were identified, some being mucus regulated. This work highlights the strong influence of the host environment in shaping bacterial survival strategies.
| S-EPMC3509433 | biostudies-literature
Project description:Accelerated lung function decline in cystic fibrosis (CF) is associated with mucoid Pseudomonas aeruginosa infection. Recent data suggest that mucoid P. aeruginosa may amenable to elimination from the airway. We aim to determine whether the initiation of an aggressive antibiotic eradication regimen upon initial discovery of mucoid P. aeruginosa in the CF airway could be successful in clearing the organism from the CF lung.We performed a retrospective analysis of patients with CF who demonstrated new growth of mucoid P. aeruginosa in an airway culture between January 2003 and December 2008. The primary endpoint was clearance of mucoid P. aeruginosa, based upon the Leeds criteria, with no further growth of mucoid P. aeruginosa cultures within 12 months of the initial discovery and treatment. Factors associated with successful clearance were also evaluated.Forty-eight of 355 patients with CF had a new diagnosis of mucoid P. aeruginosa during the study period; 15 patients underwent an eradication attempt, while 33 patients received no increase in therapy. We observed clearance of mucoid P. aeruginosa in 73.3% of patients undergoing an eradication attempt, whereas 36.6% of those that did not undergo attempted eradication cleared the organism at 1 year (P < 0.05). Prolonged mucoid P. aeruginosa airway clearance (>24 months) for mucoid P. aeruginosa was seen in 60.0% in subjects undergoing eradication compared to 21.2% (P = 0.02) in control patients. At the study conclusion, lung function was greater in subjects who underwent an eradication attempt than in patients who did not undergo an eradication attempt (FEV(1) %: 91.7% vs. 75.0%, P = 0.04).Clearance of initial mucoid P. aeruginosa from the airways of select patients with CF is possible with current antibiotic regimens, and the attempt may be associated with improved lung function.
| S-EPMC3707148 | biostudies-literature
Project description:BACKGROUND:Pseudomonas aeruginosa is the prominent bacterial pathogen in the cystic fibrosis (CF) lung and contributes to significant morbidity and mortality. Though P. aeruginosa strains initially colonizing the CF lung have a nonmucoid colony morphology, they often mutate into mucoid variants that are associated with clinical deterioration. Both nonmucoid and mucoid P. aeruginosa variants are often co-isolated on microbiological cultures of sputum collected from CF patients. With regional variation in bronchiectasis, tissue damage, inflammation, and microbial colonization, lobar distribution of nonmucoid and mucoid P. aeruginosa variants may impact local microenvironments in the CF lung, but this has not been well-studied. METHODS:We prospectively collected lobe-specific bronchoalveolar lavage (BAL) fluid from a CF patient cohort (n?=?14) using a standardized bronchoscopic protocol where collection was performed in 6 lobar regions. The lobar BAL specimens were plated on P. aeruginosa-selective media and proinflammatory cytokines (IL-1, TNF, IL-6 and IL-8) were measured via cytokine array. Correlations between infecting P. aeruginosa variants (nonmucoid, mucoid, or mixed-variant populations), the lobar regions in which these variants were found, and regional proinflammatory cytokine concentrations were measured. RESULTS:P. aeruginosa mucoid and nonmucoid variants were homogenously distributed throughout the CF lung. However, infection with mucoid variants (found within single- or mixed-variant populations) was associated with significantly greater regional inflammation. The upper and lower lobes of the CF lung did not exhibit differences in inflammatory cytokine concentrations. CONCLUSIONS:Mucoid P. aeruginosa infection is a microbial determinant of regional inflammation within the CF lung.
| S-EPMC6815243 | biostudies-literature
Project description:Pseudomonas aeruginosa is a serious threat to patients suffering from cystic fibrosis. These organisms are exposed to a unique set of selective pressures within the lung. Here, we report the draft genome sequence of a mucoid P. aeruginosa clinical isolate obtained from a cystic fibrosis patient colonized with P. aeruginosa.
| S-EPMC5690347 | biostudies-literature
Project description:Quorum quenching (QQ), a mechanism which inhibits, interferes or inactivates quorum sensing, has been investigated for control of biofilms instigated by quorum sensing process. Application of quorum quenchers (QQs) provides the possibility to investigate how different phenotypes of Pseudomonas aeruginosa (non-mucoid, mucoid, and heavily mucoid strains) modulate their gene expression to form biofilms, their quorum sensing (QS) mediated biofilm to be formed, and their virulence expressed. The mRNA expression of the AHL-mediated QS circuit and AHL-mediated virulence factors in P. aeruginosa was investigated in presence of QQs. qPCR analysis showed that farnesol and tyrosol actively reduce the expression of the synthase protein, LasI and RhlI, and prevent production of 3OC12-HSL and C4-HSL, respectively. Also, the use of farnesol and tyrosol significantly moderated gene expression for exo-proteins toxA, aprA, LasB, as well as rhlAB, which are responsible for rhamnolipid production. Our findings were promising, identifying several suppressive regulatory effects of furanone and Candida albicans QS signal molecules, tyrosol, and farnesol on the AHL-mediated P. aeruginosa QS network and related virulence factors.
| S-EPMC9283346 | biostudies-literature
Project description:Pseudomonas aeruginosa isolates from chronic lung infections often overproduce alginate, giving rise to the mucoid phenotype. Isolation of mucoid strains from chronic lung infections correlates with a poor patient outcome. The most common mutation that causes the mucoid phenotype is called mucA22 and results in a truncated form of the anti-sigma factor MucA that is continuously subjected to proteolysis. When a functional MucA is absent, the cognate sigma factor, AlgT, is no longer sequestered and continuously transcribes the alginate biosynthesis operon, leading to alginate overproduction. In this work, we report that in the absence of wild-type MucA, providing exogenous AlgT is toxic. This is intriguing, since mucoid strains endogenously possess high levels of AlgT. Furthermore, we show that suppressors of toxic AlgT production have mutations in mucP, a protease involved in MucA degradation, and provide the first atomistic model of MucP. Based on our findings, we speculate that mutations in mucP stabilize the truncated form of MucA22, rendering it functional and therefore able to reduce toxicity by properly sequestering AlgT.IMPORTANCEPseudomonas aeruginosa is an opportunistic bacterial pathogen capable of causing chronic lung infections. Phenotypes important for the long-term persistence and adaption to this unique lung ecosystem are largely regulated by the AlgT sigma factor. Chronic infection isolates often contain mutations in the anti-sigma factor mucA, resulting in uncontrolled AlgT and continuous production of alginate in addition to the expression of ∼300 additional genes. Here, we report that in the absence of wild-type MucA, AlgT overproduction is lethal and that suppressors of toxic AlgT production have mutations in the MucA protease, MucP. Since AlgT contributes to the establishment of chronic infections, understanding how AlgT is regulated will provide vital information on how P. aeruginosa is capable of causing long-term infections.
| S-EPMC7515251 | biostudies-literature
Project description:Pseudomonas aeruginosa is an opportunistic pathogenic bacterium involved in many human infections, including pneumonia, diabetic foot ulcers, and ventilator-associated pneumonia. P. aeruginosa cells usually undergo mucoid conversion during chronic lung infection in patients with cystic fibrosis (CF) and resist destruction by polymorphonuclear leukocytes (PMNs), which release free oxygen radicals (ROS), such as H2O2. PMNs are the main leucocytes in the CF sputum of patients who are infected with P. aeruginosa, which usually forms biofilms. Here, we report that PMNs or H2O2 can promote biofilm formation by mucoid P. aeruginosa FRD1 with the use of the hanging-peg method. The mucoid strain infecting CF patients overproduces alginate. In this study, PMNs and H2O2 promoted alginate production, and biofilms treated with PMNs or H2O2 exhibited higher expression of alginate genes. Additionally, PMNs increased the activity of GDP-mannose dehydrogenase, which is the key enzyme in alginate biosynthesis. Our results demonstrate that PMNs or H2O2 can enhance mucoid P. aeruginosa biofilms.
| S-EPMC6079396 | biostudies-literature
Project description:Overproduction of the exopolysaccharide alginate and conversion to a mucoid phenotype in Pseudomonas aeruginosa are markers for the onset of chronic lung infection in cystic fibrosis (CF). Alginate production is regulated by the extracytoplasmic function (ECF) sigma factor AlgU/T and the cognate anti-sigma factor MucA. Many clinical mucoid isolates carry loss-of-function mutations in mucA. These mutations, including the most common mucA22 allele, cause C-terminal truncations in MucA, indicating that an inability to regulate AlgU activity by MucA is associated with conversion to the mucoid phenotype. Here we report that a mutation in a stable mucoid strain derived from the parental strain PAO1, designated PAO581, that does not contain the mucA22 allele, was due to a single-base deletion in mucA (DeltaT180), generating another type of C-terminal truncation. A global mariner transposon screen in PAO581 for non-mucoid isolates led to the identification of three regulators of alginate production, clpP (PA1801), clpX (PA1802), and a clpP paralogue (PA3326, designated clpP2). The PAO581 null mutants of clpP, clpX and clpP2 showed decreased AlgU transcriptional activity and an accumulation of haemagglutinin (HA)-tagged N-terminal MucA protein with an apparent molecular mass of 15 kDa. The clpP and clpX mutants of a CF mucoid isolate revert to the non-mucoid phenotype. The ClpXP and ClpP2 proteins appear to be part of a proteolytic network that degrades the cytoplasmic portion of truncated MucA proteins to release the sequestered AlgU, which drives alginate biosynthesis.
| S-EPMC2995304 | biostudies-literature
Project description:Bacterial biofilms may cause chronic infections due to their ability to evade clearance by the immune system and antibiotics. The persistent biofilms induce a hyperinflammatory state that damages the surrounding host tissue. Knowledge about the components of biofilms that are responsible for provoking the harmful but inefficient immune response is limited. Flagella are known to stimulate the response of polymorphonuclear leukocytes (PMNs) to planktonic solitary bacteria. However, we provide evidence that flagella are not a prerequisite for the response of PMNs to Pseudomonas aeruginosa biofilms. Instead, we found that extracellular matrix polysaccharides in P. aeruginosa biofilms play a role in the response of PMNs toward biofilms. Using a set of P. aeruginosa mutants with the ability to produce a subset of matrix exopolysaccharides, we found that P. aeruginosa biofilms with distinct exopolysaccharide matrix components elicit distinct PMN responses. In particular, the PMNs respond aggressively toward a biofilm matrix consisting of both Psl and alginate exopolysaccharides. These findings are relevant for therapeutic strategies aimed at dampening the collateral damage associated with biofilm-based infections.
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