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(a) Mucoid colony morphology of P. aeruginosa . (b) Alginate precip- itated with ethanol from a culture of mucoid P. aeruginosa . (a) The plate on the left displays the commonly observed watery mucoid appearance on standard medium; the plate on the right has been supplemented with Ca 2 ϩ to show gelling
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Respiratory infections with Pseudomonas aeruginosa and Burkholderia cepacia play a major role in the pathogenesis of cystic fibrosis (CF). This review summarizes the latest advances in understanding host-pathogen interactions in CF with an emphasis on the role and control of conversion to mucoidy in P. aeruginosa, a phenomenon epitomizing the adapt...
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... additional, potentially significant characteristic of alg- inate is its transition from sol to gel states in its interactions with divalent actions and organic molecules. For example, al- ginate can form a gel (Fig. 2) in the presence of Ca 2 (137,167). Pederson (329) and Ertesvag et al. (118) have recently discussed the effects of the homopolymeric guluronate blocks on the gelling properties of alginate in the presence of divalent cations such as Ca 2 . The buckled chains of polyguluronic blocks, such as those found in abundance in the exine coat ...
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... and, in cooperation with AlgU, brings about strong transcription of algD (279). Activation of the algD promoter may affect other alg genes (only genes with assigned names are shown) located further downstream of algD (60a). AlgR also binds to the algC promoter (132). These events result in alginate overproduction and mucoid colony morphology (Fig. 2). AlgU most probably transcribes rpoH from its E promoter, causing expression cascade of other systems participating in defense against heat shock and oxidative ...
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... antibiotic penetration (240) contribute to the inability to erad- icate P. aeruginosa by even the most aggressive antibiotic treatments. An additional, potentially significant characteristic of alginate is its transition from sol to gel states in its interactions with divalent actions and organic molecules. For example, alginate can form a gel (Fig. 2) in the presence of Ca 2 ϩ (137, 167). Pederson (329) and Ertesvag et al. (118) have recently discussed the effects of the homopolymeric guluronate blocks on the gelling properties of alginate in the presence of divalent cations such as Ca 2 ϩ . The buckled chains of polyguluronic blocks, such as those found in abundance in the exine ...
Citations
... P. aeruginosa is increasingly resistant to conventional antibiotics, which can be compounded by the formation of biofilms on surfaces, conferring additional resistance [13]. Once P. aeruginosa produces biofilms to create chronic infections, it undergoes a sequence of changes that aggravate multidrug resistance, making difficult-to-treat infections potentially fatal, particularly in people with the hereditary condition cystic fibrosis and other immune weaknesses [14][15][16]. ...
The overuse of traditional antibiotics has resulted in bacterial resistance and seriously compromised the therapeutic efficacy of traditional antibiotics, making the exploration of new antimicrobials particularly important. Several studies have shown that bioactive peptides have become an important source of new antimicrobial drugs due to their broad-spectrum antibacterial action and lack of susceptibility to resistance. In this study, a novel bioactive peptide Nigrosin-6VL was characterised from the skin secretion of the golden cross band frog, Odorrana andersonii, by using the ‘shotgun’ cloning strategy. Modifications on the Rana Box of Nigrosin-6VL revealed its critical role in antimicrobial functions. The peptide analogue, 2170-2R, designed to preserve the Rana Box structure while enhancing cationicity, exhibited improved therapeutic efficacy, particularly against Gram-negative bacteria, with a therapeutic value of 45.27. Synergistic studies demonstrated that 2170-2R inherits the synergistic antimicrobial activities of the parent peptides and effectively enhances the antimicrobial capacity of cefepime and gentamicin against both planktonic cells and biofilms. Specifically, 2170-2R can synergise effectively with cefepime and gentamicin against different strains of P. aeruginosa biofilms. Consequently, 2170-2R holds promise as a potent antimicrobial agent developed to combat infections induced by Pseudomonas aeruginosa.
... We began our investigations by testing the antimicrobial efficacy of our peptide library against P. aeruginosa, an opportunistic gram-negative bacterium found in patients with cystic fibrosis (CF) 44,45 . MDR isolates of P. aeruginosa obtained from chronically infected CF patients were independently challenged with the peptide library using a minimum inhibitory concentration assay (MIC, defined as the lowest drug concentration required to inhibit bacterial growth). ...
The outer membrane (OM) is a hallmark feature of gram-negative bacteria that provides the species with heightened resistance against antibiotic threats while cationic antimicrobial peptides (CAPs) are natural antibiotics broadly recognized for their ability to disrupt bacterial membranes. It has been well-established that lipopolysaccharides present on the OM are among major targets of CAP activity against gram-negative species. Here we investigate how the relative distribution of charged residues along the primary peptide sequence, in conjunction with its overall hydrophobicity, affects such peptide-OM interactions in the natural CAP Ponericin W1. Using a designed peptide library derived from Ponericin W1, we determined that the consecutive placement of Lys residues at the peptide N- or C-terminus (ex. “PonN”: KKKKKKWLGSALIGALLPSVVGLFQ) enhances peptide binding affinity to OM lipopolysaccharides compared to constructs where Lys residues are interspersed throughout the primary sequence (ex. “PonAmp”: WLKKALKIGAKLLPSVVKLFKGSGQ). Antimicrobial activity against multidrug resistant strains of Pseudomonas aeruginosa was similarly found to be highest among Lys-clustered sequences. Our findings suggest that while native Ponericin W1 exerts its initial activity at the OM, Lys-clustering may be a promising means to enhance potency towards this interface, thereby augmenting peptide entry and activity at the IM, with apparent advantage against multidrug-resistant species.
... Lower respiratory tract infections are a significant public health issue because of the ease of person-to-person transmission, resulting in an even greater burden than cancer or heart disease [1,2]. Acinetobacter baumannii (Aba) [3], Klebsiella pneumoniae (Kpn) [4], and Pseudomonas aeruginosa (Pae) [5] are three common gramnegative bacteria that have been confirmed to cause respiratory tract infections. The sizes of Aba, Kpn, and Pae are generally in the range of (0.6-1.0) um × (1.0-1.6) ...
Sputum smear tests are critical for the diagnosis of respiratory diseases. Automatic segmentation of bacteria from sputum smear images is important for improving diagnostic efficiency. However, this remains a challenging task owing to the high interclass similarity among different categories of bacteria and the low contrast of the bacterial edges. To explore more levels of global pattern features to promote the distinguishing ability of bacterial categories and maintain sufficient local fine-grained features to ensure accurate localization of ambiguous bacteria simultaneously, we propose a novel dual-branch deformable cross-attention fusion network (DB-DCAFN) for accurate bacterial segmentation. Specifically, we first designed a dual-branch encoder consisting of multiple convolution and transformer blocks in parallel to simultaneously extract multilevel local and global features. We then designed a sparse and deformable cross-attention module to capture the semantic dependencies between local and global features, which can bridge the semantic gap and fuse features effectively. Furthermore, we designed a feature assignment fusion module to enhance meaningful features using an adaptive feature weighting strategy to obtain more accurate segmentation. We conducted extensive experiments to evaluate the effectiveness of DB-DCAFN on a clinical dataset comprising three bacterial categories: Acinetobacter baumannii, Klebsiella pneumoniae, and Pseudomonas aeruginosa. The experimental results demonstrate that the proposed DB-DCAFN outperforms other state-of-the-art methods and is effective at segmenting bacteria from sputum smear images.
... Pseudomonas aeruginosa is a common Gramnegative bacterium that infects immunocompromised individuals, such as cystic fibrosis (CF) patients and individuals whose normal barrier is breached due to burns, indwelling medical devices and prolonged use of antibiotics [Fagerlind et al., 2003;Govan & Deretic, 1996]. In CF patients, P. aeruginosa is a major cause of mortality and morbidity [Govan & Nelson, 1992]. ...
In this work, a sufficiently simple quorum sensing model allows one to perform detailed analytic studies to gain insights into the dynamical mechanisms in Pseudomonas aeruginosa. It is shown that an optimal rate of model parameters is essential to induce oscillations without considering time delays. Theoretical analysis and numerical simulation reveal that the delays can induce subcritical Hopf bifurcation and oscillation hysteresis. By using the center manifold and normal form theory, the explicit formulas for determining the stability and direction of periodic solutions bifurcating from Hopf bifurcations are derived. Numerical results show that the global periodic solutions bifurcating from the equilibrium exist when the delay is faraway from the first critical value. Moreover, the length of the delay can determine the amplitudes and the periods of the oscillations. A two-parameter diagram of delays is given to illustrate their crucial roles in coordinating and regulating oscillatory dynamics of the system. These results may help to further understand the dynamics of quorum sensing system in Pseudomonas aeruginosa and provide beneficial guidelines in the process of bacterial delivery of drugs.
... Similarly, ecotin of B. pseudomallei is essential for intracellular survival in murine macrophages, probably by inhibiting host proteases of the early endosome (Ireland et al., 2014). P. aeruginosa as well as B. cepacia are two major pathogens causing chronic infections in adult cystic fibrosis (CF) patients, both of which possess ecotin homologs (Govan and Deretic, 1996;Rajan and Saiman, 2002). Interestingly, P. aeruginosa and B. cepacia are opportunistic human pathogens that thrive in the lung environment as biofilms, and as such are not exposed to digestive or plasma proteases (Lavoie et al., 2011;Yaghi et al., 2020). ...
Serine protease inhibitors are a large family of proteins involved in important pathways and processes, such as inflammatory responses and blood clotting. Most are characterized by a precise mode of action, thereby targeting a narrow range of protease substrates. However, the serine-protease inhibitor ecotin is able to inhibit a broad range of serine proteases that display a wide range of specificities. This specificity is driven by special structural features which allow unique flexibility upon binding to targets. Although frequently observed in many human/animal-associated bacteria, ecotin homologs may also be found in plant-associated taxa and environmental species. The purpose of this review is to provide an update on the biological importance, role in host–microbe interactions, and evolutionary relationship between ecotin orthologs isolated from Eukaryotic and Prokaryotic species across the Tree of Life.
... (10,60,64), suggesting the biphasic response is a common observation for models of infections that is representative of outbred populations and likely more representative of human infections. Another analogous example is chronic, lifelong infections in cystic fibrosis (CF) patients (65). Some commonalities between CF infections and CAUTI are observations that there are acute and chronic phases of infection. ...
Healthcare-associated infections are major causes of complications that lead to extended hospital stays and significant medical costs. The use of medical devices, including catheters, increases the risk of bacterial colonization and infection through the presence of a foreign surface. Two outcomes are observed for catheterized patients: catheter-associated asymptomatic bacteriuria and catheter-associated urinary tract infection (CAUTI). However, the relationship between these two events remains unclear. To understand this relationship, we studied a murine model of Pseudomonas aeruginosa CAUTI. In this model, we also observe two outcomes in infected animals: acute symptoms that is associated with CAUTI and chronic colonization that is associated with asymptomatic bacteriuria. The timing of the acute outcome takes place in the first week of infection, whereas chronic colonization occurs in the second week of infection. We further showed that mutants lacking genes encoding type III secretion system (T3SS), T3SS effector proteins, T3SS injection pore, or T3SS transcriptional activation all fail to cause acute symptoms of CAUTI. Nonetheless, all mutants defective for T3SS colonized the catheter and bladders at levels similar to the parental strain. In contrast, through induction of the T3SS master regulator ExsA, all infected animals showed acute phenotypes with bacteremia. Our results demonstrated that the acute symptoms, which are analogous to CAUTI, and chronic colonization, which is analogous to asymptomatic bacteriuria, are independent events that require distinct bacterial virulence factors. Experimental delineation of asymptomatic bacteriuria and CAUTI informs different strategies for the treatment and intervention of device-associated infections.
... It is a well-known opportunistic human pathogen causing both acute and chronic diseases. Moreover, it is one of the leading causes of chronic infection in cystic fibrosis where its ability to adapt and thrive in different environments makes it incredibly difficult to treat [1,2]. The survival strategies of P. aeruginosa include its ability to form complex biofilms and secrete numerous virulence factors [3][4][5][6]. ...
Pseudomonas aeruginosa is an opportunistic pathogen that causes serious illness, especially in immunocompromised individuals, including those with cystic fibrosis. P. aeruginosa extensively forms biofilms which significantly contribute to its growth and persistence in a wide range of environments. In addition, its success can be attributed to s everal secreted proteases. Here, we investigated the aminopeptidase PaAP from P. aeruginosa , which is one of the most abundant extracellular proteins in the biofilm matrix. Increasing evidence suggests this quorum-sensing-regulated peptidase is associated with biofilm development and contributes to nutrient recycling by complementing the activity of other secreted proteases. We confirmed that post translational processing was required for activation, as a C-terminal truncation mutant possessed ~100-fold higher activity than the full-length enzyme. We determined that PaAP is a promiscuous aminopeptidase acting on unstructured regions of peptides and proteins. High-resolution crystal structures of wild type enzyme and mutants revealed the mechanism of autoinhibition, whereby the C-terminal pro-peptide locks the protease-associated (PA) domain and the catalytic peptidase domain, into a closed, inhibited conformation. Inspired by this self-regulatory mechanism and guided by structural data, we designed a highly potent small cyclic-peptide inhibitor ( K i in the nM range). This inhibitor recapitulates the deleterious phenotype observed with a PaAP deletion mutant in liquid cultures and biofilm assays and presents a path towards targeting secreted proteins in a biofilm context.
... One of the key factors for persistence of P. aeruginosa in nature is its ability to form surface attached communities known as biofilms. Biofilm formation by P. aeruginosa is considered as principle virulence factor in many chronic infections 12,15,37 . These infections are not easy to treat with antimicrobial as biofilms do have complex molecular factors leading to recalcitrance 8 . ...
Pseudomonas aeruginosa is well known nosocomial pathogen. It is recognized for hospital-related infections in immuno-compromised patients. P. aeruginosa has a plastic genome known for developing faster multidrug-resistant strains. P. aeruginosa is identified for transiting lifestyle from free-swimming to encapsulated sessile biofilms. This bacterium is notorious to cause acute infection during free swimming lifestyle (planktonic). The infections may transit to chronic form which is difficult to treat. Chronic infections are generally represented by biofilm formation. P. aeruginosa causes device and non-device related biofilm-based infections. The problem arises when biofilm infection becomes antibiotic tolerant and resistant to immune response due to restricted penetration of antimicrobials. Thus, biofilm formation creates more problem during infection as it can become untreatable and more persistent. Therefore, a detailed study of biofilm biology is a necessity. In this review, we have described infections caused by P. aeruginosa biofilms, immune response against biofilms and antibiotic tolerance mechanisms. We have also discussed how in vitro biofilms are studied in lab. Further we have described composition of biofilm matrix and their sequential formation. In addition, P. aeruginosa biofilm formation is tightly regulated mainly by three ways- changing c-di-GMP level, two components signaling (GAC/RET/LAD) and quorum sensing (QS). This review gives insight to different aspect of P. aeruginosa biofilms, one of the topmost model organism studied in infection biology.
... These chronic pulmonary infections are associated with a rapid decline in lung functions, high morbidity and short life expectancy [4]. One of the most striking hallmarks of P. aeruginosa in chronically infected CF patients is the conversion to a mucoid phenotype of the mucus due to the increased production of alginates [5][6][7], natural polymers composed of mannuronic and guluronic acid units arranged in a block-wise pattern [8]. Alginates overproduction can contribute to a strong inflammatory response sustained by immune cells that can influence lung epithelial cells [9][10][11]. ...
Cystic fibrosis (CF) is a disease characterized by the production of viscous mucoid secretions in multiple organs, particularly the airways. The pathological increase of proteins, mucin and biological polymers determines their arrangement into a three-dimensional polymeric network, affecting the whole mucus and impairing the muco-ciliary clearance which promotes inflammation and bacterial infection. Thus, to improve the efficacy of the drugs usually applied in CF therapy (e.g., mucolytics, anti-inflammatory and antibiotics), an in-depth understanding of the mucus nanostructure is of utmost importance. Drug diffusivity inside a gel-like system depends on the ratio between the diffusing drug molecule radius and the mesh size of the network. Based on our previous findings, we propose the combined use of rheology and low field NMR to study the mesh size distribution of the sputum from CF patients. Specifically, we herein explore the effects of chest physiotherapy on CF sputum characteristic as evaluated by rheology, low field NMR and the drug penetration through the mucus via mathematical simulation. These data show that chest physiotherapy has beneficial effects on patients, as it favourably modifies sputum and enhances drug penetration through the respiratory mucus.
Graphical abstract
... The RpoE (AlgU) sigma factor add to tolerance against oxidative, osmotic and heat stresses in P. syringae and P. aeruginosa which are encoded by mucABCD genes. When bacteria are exposed to adverse environment, the MucB-MucA-AlgU complex destabilize which leads to release of AlgU sigma factor into the cytosol which become active (Martin et al. 1994;Keith and Bender 1999;Schurr and Deretic 1997;Schurr et al. 1995;Govan and Deretic 1996;Mathee 1997). ATP and ppGpp levels are enhanced by Polyhydroxyalkanoates (PHAs) availability and expression of RpoS gene are induced by ppGpp (Gentry et al. 1993). ...
Fluorescent pseudomonades are considered important bioagents in agriculture due to their rhizospheric competence, biocontrol abilities and biofertilizing properties. These bacteria exhibit profound diversity due to their significant genotypic, phenotypic, physiological, biological and functional variability. Due to these diversities, they are capable of degrading a number of organic substances viz. aromatic, halogenated compounds and many organic industrial effluents. Further, they can produce a variety of antagonists, plant hormones and other biochemical metabolites. Phenotypically, they have been divided into biotypes and biovars which is reflected in their genotypic structures including their chromosomes and other genetic materials. They are the most abundant bacteria which inhabit most of the niches on the earth viz. terrestrial, marine, freshwater and glaciers. Recently, biotechnological interventions are being increasingly used in the development of new strains of these bacteria and to understand their interaction in rhizosphere. With the advent of these technologies, bacterial strains with enhanced plant growth promoting abilities and disease resistance inducing capabilities are being developed. These novel strains are having increased antimicrobial production capabilities with higher rhizospheric competence and also more compatible to pesticides used in agriculture. Some of the genes of these bacteria are also used for development of disease et al. 280 resistant GMO crops. The molecular technologies like rRNA-DNA hybridization based on 16S rRNA, REP, ERIC and BOX-PCR help in the diversity study and classification of this bacterium. These biotechnological applications help in the transformation of these fluorescent pseudomonades into better bioagents which are more assessable and reliable to the farmers as tool in sustainable agriculture.
