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Gheorghita AA, Wozniak DJ, Parsek MR, Howell PL. Pseudomonas aeruginosa biofilm exopolysaccharides: assembly, function, and degradation. FEMS Microbiol Rev 2023; 47:fuad060. [PMID: 37884397 PMCID: PMC10644985 DOI: 10.1093/femsre/fuad060] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/21/2023] [Revised: 10/04/2023] [Accepted: 10/25/2023] [Indexed: 10/28/2023] Open
Abstract
The biofilm matrix is a fortress; sheltering bacteria in a protective and nourishing barrier that allows for growth and adaptation to various surroundings. A variety of different components are found within the matrix including water, lipids, proteins, extracellular DNA, RNA, membrane vesicles, phages, and exopolysaccharides. As part of its biofilm matrix, Pseudomonas aeruginosa is genetically capable of producing three chemically distinct exopolysaccharides - alginate, Pel, and Psl - each of which has a distinct role in biofilm formation and immune evasion during infection. The polymers are produced by highly conserved mechanisms of secretion, involving many proteins that span both the inner and outer bacterial membranes. Experimentally determined structures, predictive modelling of proteins whose structures are yet to be solved, and structural homology comparisons give us insight into the molecular mechanisms of these secretion systems, from polymer synthesis to modification and export. Here, we review recent advances that enhance our understanding of P. aeruginosa multiprotein exopolysaccharide biosynthetic complexes, and how the glycoside hydrolases/lyases within these systems have been commandeered for antimicrobial applications.
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Affiliation(s)
- Andreea A Gheorghita
- Program in Molecular Medicine, Peter Gilgan Centre for Research and Learning, The Hospital for Sick Children, 686 Bay St, Toronto, ON M5G 0A4, Canada
- Department of Biochemistry, University of Toronto, Medical Science Building, 1 King's College Cir, Toronto, ON M5S 1A8, Canada
| | - Daniel J Wozniak
- Department of Microbial Infection and Immunity, The Ohio State University College of Medicine, 776 Biomedical Research Tower, 460 W 12th Ave, Columbus, OH 43210, United States
- Department of Microbiology, The Ohio State University College, Biological Sciences Bldg, 105, 484 W 12th Ave, Columbus, OH 43210, United States
| | - Matthew R Parsek
- Department of Microbiology, University of Washington, Health Sciences Bldg, 1705 NE Pacific St, Seattle, WA 98195-7735, United States
| | - P Lynne Howell
- Program in Molecular Medicine, Peter Gilgan Centre for Research and Learning, The Hospital for Sick Children, 686 Bay St, Toronto, ON M5G 0A4, Canada
- Department of Biochemistry, University of Toronto, Medical Science Building, 1 King's College Cir, Toronto, ON M5S 1A8, Canada
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The Effects of HP0044 and HP1275 Knockout Mutations on the Structure and Function of Lipopolysaccharide in Helicobacter pylori Strain 26695. Biomedicines 2022; 10:biomedicines10010145. [PMID: 35052824 PMCID: PMC8773439 DOI: 10.3390/biomedicines10010145] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/12/2021] [Revised: 01/06/2022] [Accepted: 01/07/2022] [Indexed: 02/07/2023] Open
Abstract
Helicobacter pylori infection is associated with several gastric diseases, including gastritis, peptic ulcer, gastric adenocarcinoma and mucosa-associated lymphatic tissue (MALT) lymphoma. Due to the prevalence and severeness of H. pylori infection, a thorough understanding of this pathogen is necessary. Lipopolysaccharide, one of the major virulence factors of H. pylori, can exert immunomodulating and immunostimulating functions on the host. In this study, the HP0044 and HP1275 genes were under investigation. These two genes potentially encode GDP-D-mannose dehydratase (GMD) and phosphomannomutase (PMM)/phosphoglucomutase (PGM), respectively, and are involved in the biosynthesis of fucose. HP0044 and HP1275 knockout mutants were generated; both mutants displayed a truncated LPS, suggesting that the encoded enzymes are not only involved in fucose production but are also important for LPS construction. In addition, these two gene knockout mutants exhibited retarded growth, increased surface hydrophobicity and autoaggregation as well as being more sensitive to the detergent SDS and the antibiotic novobiocin. Furthermore, the LPS-defective mutants also had significantly reduced bacterial infection, adhesion and internalization in the in vitro cell line model. Moreover, disruptions of the HP0044 and HP1275 genes in H. pylori altered protein sorting into outer membrane vesicles. The critical roles of HP0044 and HP1275 in LPS biosynthesis, bacterial fitness and pathogenesis make them attractive candidates for drug inventions against H. pylori infection.
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Upmanyu K, Haq QMR, Singh R. Factors mediating Acinetobacter baumannii biofilm formation: Opportunities for developing therapeutics. CURRENT RESEARCH IN MICROBIAL SCIENCES 2022; 3:100131. [PMID: 35909621 PMCID: PMC9325880 DOI: 10.1016/j.crmicr.2022.100131] [Citation(s) in RCA: 8] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022] Open
Abstract
A. baumannii rapidly acquires antimicrobial resistance and causes biofilm associated infections. Strategies to target intrinsic factors mediating A. baumannii biofilm formation offer therapeutic prospects. Antimicrobial polymers and coating medical devices with antibiofilm agents may prevent biofilm associated infections. Biofilm matrix or regulatory mechanisms such as quorum sensing are potential targets for treating chronic infections. Phage therapy, photodynamic therapy and nanoparticle therapy are novel promising approaches for treating biofilm associated infections.
Acinetobacter baumannii has notably become a superbug due to its mounting risk of infection and escalating rates of antimicrobial resistance, including colistin, the last-resort antibiotic. Its propensity to form biofilm on biotic and abiotic surfaces has contributed to the majority of nosocomial infections. Bacterial cells in biofilms are resistant to antibiotics and host immune response, and pose challenges in treatment. Therefore current scenario urgently requires the development of novel therapeutic strategies for successful treatment outcomes. This article provides a holistic understanding of sequential events and regulatory mechanisms directing A. baumannii biofilm formation. Understanding the key factors functioning and regulating the biofilm machinery of A. baumannii will provide us insight to develop novel approaches to combat A. baumannii infections. Further, the review article deliberates promising strategies for the prevention of biofilm formation on medically relevant substances and potential therapeutic strategies for the eradication of preformed biofilms which can help tackle biofilm-associated A. baumannii infections. Advances in emerging therapeutic opportunities such as phage therapy, nanoparticle therapy and photodynamic therapy are also discussed to comprehend the current scenario and future outlook for the development of successful treatment against biofilm-associated A. baumannii infections.
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Specific and Global RNA Regulators in Pseudomonas aeruginosa. Int J Mol Sci 2021; 22:ijms22168632. [PMID: 34445336 PMCID: PMC8395346 DOI: 10.3390/ijms22168632] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/19/2021] [Revised: 08/05/2021] [Accepted: 08/08/2021] [Indexed: 01/20/2023] Open
Abstract
Pseudomonas aeruginosa (Pae) is an opportunistic pathogen showing a high intrinsic resistance to a wide variety of antibiotics. It causes nosocomial infections that are particularly detrimental to immunocompromised individuals and to patients suffering from cystic fibrosis. We provide a snapshot on regulatory RNAs of Pae that impact on metabolism, pathogenicity and antibiotic susceptibility. Different experimental approaches such as in silico predictions, co-purification with the RNA chaperone Hfq as well as high-throughput RNA sequencing identified several hundreds of regulatory RNA candidates in Pae. Notwithstanding, using in vitro and in vivo assays, the function of only a few has been revealed. Here, we focus on well-characterized small base-pairing RNAs, regulating specific target genes as well as on larger protein-binding RNAs that sequester and thereby modulate the activity of translational repressors. As the latter impact large gene networks governing metabolism, acute or chronic infections, these protein-binding RNAs in conjunction with their cognate proteins are regarded as global post-transcriptional regulators.
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Panlilio H, Lam AK, Heydarian N, Haight T, Wouters CL, Moen EL, Rice CV. Dual-Function Potentiation by PEG-BPEI Restores Activity of Carbapenems and Penicillins against Carbapenem-Resistant Enterobacteriaceae. ACS Infect Dis 2021; 7:1657-1665. [PMID: 33945257 PMCID: PMC8689638 DOI: 10.1021/acsinfecdis.0c00863] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
The rise of life-threatening carbapenem-resistant Enterobacteriaceae (CRE) infections has become a critical medical threat. Some of the most dangerous CRE bacteria can produce enzymes that degrade a wide range of antibiotics, including carbapenems and β-lactams. Infections by CRE have a high mortality rate, and survivors can have severe morbidity from treatment with toxic last-resort antibiotics. CRE have mobile genetic elements that transfer resistance genes to other species. These bacteria also circulate throughout the healthcare system. The mobility and spread of CRE need to be curtailed, but these goals are impeded by having few agents that target a limited range of pathogenic CRE species. Against CRE possessing the metallo-β-lactamase NDM-1, Klebsiella pneumoniae ATCC BAA-2146 and Escherichia coli ATCC BAA-2452, the potentiation of meropenem and imipenem is possible with low-molecular weight branched polyethylenimine (600 Da BPEI) and its poly(ethylene glycol) (PEG)ylated derivative (PEG-BPEI) that has a low in vivo toxicity. The mechanism of action is elucidated with fluorescence assays of drug influx and isothermal calorimetry data showing the chelation of essential Zn2+ ions. These results suggested that 600 Da BPEI and PEG-BPEI may also improve the uptake of antibiotics and β-lactamase inhibitors. Indeed, the CRE E. coli strain is rendered susceptible to the combination of piperacillin and tazobactam. These results expand the possible utility of 600 Da BPEI potentiators, where previously we have demonstrated the ability to improve antibiotic efficacy against antibiotic resistant clinical isolates of Pseudomonas aeruginosa, Staphylococcus aureus, and Staphylococcus epidermidis.
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Affiliation(s)
- Hannah Panlilio
- Department of Chemistry and Biochemistry, Stephenson Life Sciences Research Center, University of Oklahoma, 101 Stephenson Parkway, Norman, Oklahoma 73019, United States
| | - Anh K Lam
- Department of Chemistry and Biochemistry, Stephenson Life Sciences Research Center, University of Oklahoma, 101 Stephenson Parkway, Norman, Oklahoma 73019, United States
| | - Neda Heydarian
- Department of Chemistry and Biochemistry, Stephenson Life Sciences Research Center, University of Oklahoma, 101 Stephenson Parkway, Norman, Oklahoma 73019, United States
| | - Tristan Haight
- Department of Chemistry and Biochemistry, Stephenson Life Sciences Research Center, University of Oklahoma, 101 Stephenson Parkway, Norman, Oklahoma 73019, United States
| | - Cassandra L Wouters
- Department of Chemistry and Biochemistry, Stephenson Life Sciences Research Center, University of Oklahoma, 101 Stephenson Parkway, Norman, Oklahoma 73019, United States
| | - Erika L Moen
- Department of Chemistry and Biochemistry, Stephenson Life Sciences Research Center, University of Oklahoma, 101 Stephenson Parkway, Norman, Oklahoma 73019, United States
| | - Charles V Rice
- Department of Chemistry and Biochemistry, Stephenson Life Sciences Research Center, University of Oklahoma, 101 Stephenson Parkway, Norman, Oklahoma 73019, United States
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Luo J, Li X, Zhang J, Feng A, Xia M, Zhou M. Global regulator engineering enhances bioelectricity generation in Pseudomonas aeruginosa-inoculated MFCs. Biosens Bioelectron 2020; 163:112269. [PMID: 32568691 DOI: 10.1016/j.bios.2020.112269] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/15/2020] [Revised: 04/21/2020] [Accepted: 04/30/2020] [Indexed: 01/24/2023]
Abstract
The electricigens with high-electroactivity is essential for resolving the low electricity power output (EPT) of microbial fuel cells (MFCs). However, the manipulation by single functional genes shows limitation because electroactivity is a complex phenotype controlled by multiple genes. Herein, global regulator engineering (GRE) was developed to optimize the electroactivity of an isolated strain (Pseudomonas aeruginosa P3-A-11) using an exogenous global regulator IrrE (ionizing radiation resistance E linkage group) as an object. The GRE was implemented through in vitro random mutagenesis by error-prone PCR and in vivo high-through screening comprised of cultures color assay, PYO measurement and MFCs operation. Four mutants with higher electroactivity were obtained, among which, the mutant 11/M2-59 not only displayed the maximal power density, but also exhibited stronger salt tolerance, consequently showing good performance of MFCs in the presence of salt. Apart from the reduced internal resistance, the increase in phenazines amounts primarily contributed to EPT improvement, which was realized by enhancing the core biosynthesis pathway and affecting other pathways (such as central metabolism pathway, quorum sensing system, regulatory network). Notably, IrrE exerted its positive effect on electroactivity even without native regulators (such as PmpR and RpoS). In addition, the significant fluctuations in expression levels of stress-responsive genes mediated by GRE were closely associated with the enhanced salt tolerance. This work demonstrated that GRE was an effective approach for simultaneously optimizing multiple phenotypes (such as electroactivity and stress tolerance), and thus would provide more opportunities to create high-efficiency electricigens and further promoted the practical application of MFCs.
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Affiliation(s)
- Jianmei Luo
- Key Laboratory of Industrial Fermentation Microbiology (Tianjin University of Science &Technology), Ministry of Education, Tianjin Key Lab of Industrial Microbiology, College of Biotechnology, Tianjin University of Science and Technology, Tianjin, 300457, PR China.
| | - Xiao Li
- Key Laboratory of Industrial Fermentation Microbiology (Tianjin University of Science &Technology), Ministry of Education, Tianjin Key Lab of Industrial Microbiology, College of Biotechnology, Tianjin University of Science and Technology, Tianjin, 300457, PR China
| | - Jingmei Zhang
- Key Laboratory of Industrial Fermentation Microbiology (Tianjin University of Science &Technology), Ministry of Education, Tianjin Key Lab of Industrial Microbiology, College of Biotechnology, Tianjin University of Science and Technology, Tianjin, 300457, PR China
| | - An Feng
- Key Laboratory of Industrial Fermentation Microbiology (Tianjin University of Science &Technology), Ministry of Education, Tianjin Key Lab of Industrial Microbiology, College of Biotechnology, Tianjin University of Science and Technology, Tianjin, 300457, PR China
| | - Menglei Xia
- Key Laboratory of Industrial Fermentation Microbiology (Tianjin University of Science &Technology), Ministry of Education, Tianjin Key Lab of Industrial Microbiology, College of Biotechnology, Tianjin University of Science and Technology, Tianjin, 300457, PR China
| | - Minghua Zhou
- Key Laboratory of Pollution Process and Environmental Criteria, Ministry of Education, Tianjin Key Laboratory of Urban Ecology Environmental Remediation and Pollution Control, College of Environmental Science and Engineering, Nankai University, Tianjin, 300350, PR China.
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Lam AK, Panlilio H, Pusavat J, Wouters CL, Moen EL, Rice CV. Overcoming Multidrug Resistance and Biofilms of Pseudomonas aeruginosa with a Single Dual-Function Potentiator of β-Lactams. ACS Infect Dis 2020; 6:1085-1097. [PMID: 32223216 PMCID: PMC7233300 DOI: 10.1021/acsinfecdis.9b00486] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/08/2023]
Abstract
Clinicians prescribe hundreds of millions of β-lactam antibiotics to treat the majority of patients presenting with bacterial infections. Patient outcomes are positive unless resistant bacteria, such as Pseudomonas aeruginosa (P. aeruginosa), are present. P. aeruginosa has both intrinsic and acquired antibiotic resistance, making clinical management of infection a real challenge, particularly when these bacteria are sequestered in biofilms. These problems would be alleviated if, upon the initial presentation of bacterial infection symptoms, clinicians were able to administer an antibiotic that kills both susceptible and otherwise resistant bacteria and eradicates biofilms. As the most common class of antibiotics, β-lactams could be used in a new drug if the leading causes of β-lactam antibiotic resistance, permeation barriers from lipopolysaccharide, efflux pumps, and β-lactamase enzymes, were also defeated. Against P. aeruginosa and their biofilms, the potency of β-lactam antibiotics is restored with 600 Da branched polyethylenimine (600 Da BPEI). Checkerboard assays using microtiter plates demonstrate the potentiation of piperacillin, cefepime, Meropenem, and erythromycin antibiotics. Growth curves demonstrate that only a combination of 600 Da BPEI and piperacillin produces growth inhibition against antibiotic resistant P. aeruginosa. Scanning electron microscopy (SEM) was used to confirm that the combination treatment leads to abnormal P. aeruginosa morphology. Data collected with isothermal titration calorimetry and fluorescence spectroscopy demonstrate a mechanism of action in which potentiation at low concentrations of 600 Da BPEI reduces diffusion barriers from lipopolysaccharides without disrupting the outer membrane itself. Coupled with the ability to overcome a reduction in antibiotic activity created by biofilm exopolymers, targeting anionic sites on lipopolysaccharides and biofilm exopolysaccharides with the same compound provides new opportunities to counter the rise of multidrug-resistant infections.
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Affiliation(s)
- Anh K Lam
- Department of Chemistry and Biochemistry, Stephenson Life Sciences Research Center, University of Oklahoma, 101 Stephenson Parkway, Norman, Oklahoma 73019, United States
| | - Hannah Panlilio
- Department of Chemistry and Biochemistry, Stephenson Life Sciences Research Center, University of Oklahoma, 101 Stephenson Parkway, Norman, Oklahoma 73019, United States
| | - Jennifer Pusavat
- Department of Chemistry and Biochemistry, Stephenson Life Sciences Research Center, University of Oklahoma, 101 Stephenson Parkway, Norman, Oklahoma 73019, United States
| | - Cassandra L Wouters
- Department of Chemistry and Biochemistry, Stephenson Life Sciences Research Center, University of Oklahoma, 101 Stephenson Parkway, Norman, Oklahoma 73019, United States
| | - Erika L Moen
- Department of Chemistry and Biochemistry, Stephenson Life Sciences Research Center, University of Oklahoma, 101 Stephenson Parkway, Norman, Oklahoma 73019, United States
| | - Charles V Rice
- Department of Chemistry and Biochemistry, Stephenson Life Sciences Research Center, University of Oklahoma, 101 Stephenson Parkway, Norman, Oklahoma 73019, United States
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Enhancement of bioelectricity generation via heterologous expression of IrrE in Pseudomonas aeruginosa-inoculated MFCs. Biosens Bioelectron 2018; 117:23-31. [PMID: 29879584 DOI: 10.1016/j.bios.2018.05.052] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/03/2017] [Revised: 02/28/2018] [Accepted: 05/28/2018] [Indexed: 01/31/2023]
Abstract
Low electricity power output (EPT) is still the main bottleneck limited the industrial application of microbial fuel cells (MFCs). Herein, EPT enhancement by introducing an exogenous global regulator IrrE derived from Deinococcus radiodurans into electrochemically active bacteria (EAB) was explored using Pseudomonas aeruginosa PAO1 as a model strain, achieving a power density 71% higher than that of the control strain. Moreover, IrrE-expressing strain exhibited a remarkable increase in the total amount of electron shuttles (majorly phenazines compounds) and a little decrease in internal resistance, which should underlie the enhancement in extracellular electron transfer (EET) efficiency and EPT. Strikingly, IrrE significantly affected substrate utilization profiling, improved cell growth characterization and cell tolerance to various stresses. Further quantitative RT-PCR analysis revealed that IrrE led to many differentially expressed genes, which were responsible for phenazines core biosynthesis, biofilm formation, QS systems, transcriptional regulation, glucose metabolism and general stress response. The results substantiated that targeting cellular regulatory network by the introduction of exogenous global regulators could be a facile and promising approach for the enhancement of bioelectricity generation and cell multiple phenotypes, and thus would be of great potential application in the practical MFCs.
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Analysis of Pseudomonas aeruginosa PAO1 Biofilm Protein Profile After Exposure to n-Butanolic Cyclamen coum Extract Alone and in Combination with Ciprofloxacin. Appl Biochem Biotechnol 2017; 182:1444-1457. [PMID: 28138928 DOI: 10.1007/s12010-017-2409-4] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/22/2016] [Accepted: 01/11/2017] [Indexed: 01/08/2023]
Abstract
Pseudomonas aeruginosa biofilm-related infections are the major cause of premature death in cystic fibrosis patients. Strategies to induce biofilm dispersal are of interest, because of their potential in preventing biofilm-related infections. Our previous work demonstrated that n-butanolic Cyclamen coum extract with ciprofloxacin could eliminate 1- and 3-day-old P. aeruginosa PAO1 biofilms. To gain new insights into the role of C. coum extract and its synergistic effect with ciprofloxacin in eliminating P. aeruginosa PAO1 biofilms, two-dimensional gel electrophoresis (2-DE) in combination with mass spectrometry-based protein identification were used. Changes in the bacterial protein expression were analyzed when 3-day-old biofilm cells were exposed to the C. coum extract alone and in combination with ciprofloxacin. Proteins involved in alginate biosynthesis, quorum sensing, adaptation/protection, carbohydrate and amino acid metabolism showed a weaker expression in the C. coum extract-ciprofloxacin-treated biofilm cells compared to those in the untreated cells. Interestingly, the proteome of C. coum extract-ciprofloxacin-treated biofilm revealed more resemblance to the planktonic phenotype than to the biofilm phenotype. It appears that saponin extract in combination with ciprofloxacin causes biofilm disruption due to several mechanisms such as motility induction, cell envelope integrity perturbation, stress protein expression reduction, and more importantly, signal transduction perturbation. In conclusion, exposure to a combination of biofilm dispersal such as saponin extract and antimicrobial agents may offer a novel strategy to control preestablished, persistent P. aeruginosa biofilms and biofilm-related infections.
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Characterization of the algC gene expression pattern in the multidrug resistant Acinetobacter baumannii AIIMS 7 and correlation with biofilm development on abiotic surface. ScientificWorldJournal 2014; 2014:593546. [PMID: 25544957 PMCID: PMC4269089 DOI: 10.1155/2014/593546] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/30/2014] [Revised: 11/10/2014] [Accepted: 11/10/2014] [Indexed: 01/06/2023] Open
Abstract
Relative quantification of algC gene expression was evaluated in the multidrug resistant strain Acinetobacter baumannii AIIMS 7 biofilm (3 to 96 h, on polystyrene surface) compared to the planktonic counterparts. Comparison revealed differential algC expression pattern with maximum 81.59-fold increase in biofilm cells versus 3.24-fold in planktonic cells (P < 0.05). Expression levels strongly correlated with specific biofilm stages (scale of 3 to 96 h), coinciding maximum at initial surface attachment stage (9 h) and biofilm maturation stage (48 h). Cloning, heterologous expression, and bioinformatics analyses indicated algC gene product as the bifunctional enzyme phosphomannomutase/phosphoglucomutase (PMM/PGM) of ∼ 53 kDa size, which augmented biofilms significantly in algC clones compared to controls (lacking algC gene), further localized by scanning electron microscopy. Moreover, molecular dynamics analysis on the three-dimensional structure of PMM/PGM (simulated up to 10 ns) revealed enzyme structure as stable and similar to that in P. aeruginosa (synthesis of alginate and lipopolysaccharide core) and involved in constitution of biofilm EPS (extracellular polymeric substances). Our observation on differential expression pattern of algC having strong correlation with important biofilm stages, scanning electron-microscopic evidence of biofilm augmentation taken together with predictive enzyme functions via molecular dynamic (MD) simulation, proposes a new basis of A. baumannii AIIMS 7 biofilm development on inanimate surfaces.
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Musafer HK, Kuchma SL, Naimie AA, Schwartzman JD, Al-Mathkhury HJF, O'Toole GA. Investigating the link between imipenem resistance and biofilm formation by Pseudomonas aeruginosa. MICROBIAL ECOLOGY 2014; 68:111-120. [PMID: 24435545 PMCID: PMC8978818 DOI: 10.1007/s00248-013-0361-6] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/07/2013] [Accepted: 12/23/2013] [Indexed: 06/03/2023]
Abstract
Pseudomonas aeruginosa, a ubiquitous environmental organism, is a difficult-to-treat opportunistic pathogen due to its broad-spectrum antibiotic resistance and its ability to form biofilms. In this study, we investigate the link between resistance to a clinically important antibiotic, imipenem, and biofilm formation. First, we observed that the laboratory strain P. aeruginosa PAO1 carrying a mutation in the oprD gene, which confers resistance to imipenem, showed a modest reduction in biofilm formation. We also observed an inverse relationship between imipenem resistance and biofilm formation for imipenem-resistant strains selected in vitro, as well as for clinical isolates. We identified two clinical isolates of P. aeruginosa from the sputum of cystic fibrosis patients that formed robust biofilms, but were sensitive to imipenem (MIC ≤ 2 μg/ml). To test the hypothesis that there is a general link between imipenem resistance and biofilm formation, we performed transposon mutagenesis of these two clinical strains to identify mutants defective in biofilm formation, and then tested these mutants for imipenem resistance. Analysis of the transposon mutants revealed a role for previously described biofilm factors in these clinical isolates of P. aeruginosa, including mutations in the pilY1, pilX, pilW, algC, and pslI genes, but none of the biofilm-deficient mutants became imipenem resistant (MIC ≥ 8 μg/ml), arguing against a general link between biofilm formation and resistance to imipenem. Thus, assessing biofilm formation capabilities of environmental isolates is unlikely to serve as a good predictor of imipenem resistance. We also discuss our findings in light of the limited literature addressing planktonic antibiotic resistance factors that impact biofilm formation.
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Affiliation(s)
- Hadeel K Musafer
- Department of Biology, College of Science, University of Baghdad, Baghdad, Iraq
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12
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Okkotsu Y, Little AS, Schurr MJ. The Pseudomonas aeruginosa AlgZR two-component system coordinates multiple phenotypes. Front Cell Infect Microbiol 2014; 4:82. [PMID: 24999454 PMCID: PMC4064291 DOI: 10.3389/fcimb.2014.00082] [Citation(s) in RCA: 44] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/31/2014] [Accepted: 06/02/2014] [Indexed: 01/28/2023] Open
Abstract
Pseudomonas aeruginosa is an opportunistic pathogen that causes a multitude of infections. These infections can occur at almost any site in the body and are usually associated with a breach of the innate immune system. One of the prominent sites where P. aeruginosa causes chronic infections is within the lungs of cystic fibrosis patients. P. aeruginosa uses two-component systems that sense environmental changes to differentially express virulence factors that cause both acute and chronic infections. The P. aeruginosa AlgZR two component system is one of its global regulatory systems that affects the organism's fitness in a broad manner. This two-component system is absolutely required for two P. aeruginosa phenotypes: twitching motility and alginate production, indicating its importance in both chronic and acute infections. Additionally, global transcriptome analyses indicate that it regulates the expression of many different genes, including those associated with quorum sensing, type IV pili, type III secretion system, anaerobic metabolism, cyanide and rhamnolipid production. This review examines the complex AlgZR regulatory network, what is known about the structure and function of each protein, and how it relates to the organism's ability to cause infections.
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Affiliation(s)
- Yuta Okkotsu
- Department of Microbiology, University of Colorado School of Medicine Aurora, CO, USA
| | - Alexander S Little
- Department of Microbiology, University of Colorado School of Medicine Aurora, CO, USA
| | - Michael J Schurr
- Department of Microbiology, University of Colorado School of Medicine Aurora, CO, USA
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Hay ID, Ur Rehman Z, Moradali MF, Wang Y, Rehm BHA. Microbial alginate production, modification and its applications. Microb Biotechnol 2013; 6:637-50. [PMID: 24034361 PMCID: PMC3815931 DOI: 10.1111/1751-7915.12076] [Citation(s) in RCA: 155] [Impact Index Per Article: 14.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/09/2013] [Revised: 06/25/2013] [Accepted: 07/06/2013] [Indexed: 11/29/2022] Open
Abstract
Alginate is an important polysaccharide used widely in the food, textile, printing and pharmaceutical industries for its viscosifying, and gelling properties. All commercially produced alginates are isolated from farmed brown seaweeds. These algal alginates suffer from heterogeneity in composition and material properties. Here, we will discuss alginates produced by bacteria; the molecular mechanisms involved in their biosynthesis; and the potential to utilize these bacterially produced or modified alginates for high-value applications where defined material properties are required.
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Affiliation(s)
- Iain D Hay
- Institute of Fundamental Sciences, Massey University, Private Bag 11222, Palmerston North, New Zealand
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Fazli M, McCarthy Y, Givskov M, Ryan RP, Tolker-Nielsen T. The exopolysaccharide gene cluster Bcam1330-Bcam1341 is involved in Burkholderia cenocepacia biofilm formation, and its expression is regulated by c-di-GMP and Bcam1349. Microbiologyopen 2012; 2:105-22. [PMID: 23281338 PMCID: PMC3584217 DOI: 10.1002/mbo3.61] [Citation(s) in RCA: 42] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/23/2012] [Revised: 11/07/2012] [Accepted: 11/13/2012] [Indexed: 12/25/2022] Open
Abstract
In Burkholderia cenocepacia, the second messenger cyclic diguanosine monophosphate (c-di-GMP) has previously been shown to positively regulate biofilm formation and the expression of cellulose and type-I fimbriae genes through binding to the transcriptional regulator Bcam1349. Here, we provide evidence that cellulose and type-I fimbriae are not involved in B. cenocepacia biofilm formation in flow chambers, and we identify a novel Bcam1349/c-di-GMP-regulated exopolysaccharide gene cluster which is essential for B. cenocepacia biofilm formation. Overproduction of Bcam1349 in trans promotes wrinkly colony morphology, pellicle, and biofilm formation in B. cenocepacia. A screen for transposon mutants unable to respond to the overproduction of Bcam1349 led to the identification of a 12-gene cluster, Bcam1330-Bcam1341, the products of which appear to be involved in the production of a putative biofilm matrix exopolysaccharide and to be essential for flow-chamber biofilm formation. We demonstrate that Bcam1349 binds to the promoter region of genes in the Bcam1330-Bcam1341 cluster and that this binding is enhanced by the presence of c-di-GMP. Furthermore, we demonstrate that overproduction of both c-di-GMP and Bcam1349 leads to increased transcription of these genes, indicating that c-di-GMP and Bcam1349 functions together in regulating exopolysaccharide production from the Bcam1330-Bcam1341 gene cluster. Our results suggest that the product encoded by the Bcam1330-Bcam1341 gene cluster is a major exopolysaccharide that provides structural stability to the biofilms formed by B. cenocepacia, and that its production is regulated by c-di-GMP through binding to and promotion of the activity of the transcriptional regulator Bcam1349.
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Affiliation(s)
- Mustafa Fazli
- Department of International Health, Immunology and Microbiology, Faculty of Health Sciences, University of Copenhagen, Copenhagen, Denmark
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Franklin MJ, Nivens DE, Weadge JT, Howell PL. Biosynthesis of the Pseudomonas aeruginosa Extracellular Polysaccharides, Alginate, Pel, and Psl. Front Microbiol 2011; 2:167. [PMID: 21991261 PMCID: PMC3159412 DOI: 10.3389/fmicb.2011.00167] [Citation(s) in RCA: 343] [Impact Index Per Article: 26.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/15/2011] [Accepted: 07/19/2011] [Indexed: 12/30/2022] Open
Abstract
Pseudomonas aeruginosa thrives in many aqueous environments and is an opportunistic pathogen that can cause both acute and chronic infections. Environmental conditions and host defenses cause differing stresses on the bacteria, and to survive in vastly different environments, P. aeruginosa must be able to adapt to its surroundings. One strategy for bacterial adaptation is to self-encapsulate with matrix material, primarily composed of secreted extracellular polysaccharides. P. aeruginosa has the genetic capacity to produce at least three secreted polysaccharides; alginate, Psl, and Pel. These polysaccharides differ in chemical structure and in their biosynthetic mechanisms. Since alginate is often associated with chronic pulmonary infections, its biosynthetic pathway is the best characterized. However, alginate is only produced by a subset of P. aeruginosa strains. Most environmental and other clinical isolates secrete either Pel or Psl. Little information is available on the biosynthesis of these polysaccharides. Here, we review the literature on the alginate biosynthetic pathway, with emphasis on recent findings describing the structure of alginate biosynthetic proteins. This information combined with the characterization of the domain architecture of proteins encoded on the Psl and Pel operons allowed us to make predictive models for the biosynthesis of these two polysaccharides. The results indicate that alginate and Pel share certain features, including some biosynthetic proteins with structurally or functionally similar properties. In contrast, Psl biosynthesis resembles the EPS/CPS capsular biosynthesis pathway of Escherichia coli, where the Psl pentameric subunits are assembled in association with an isoprenoid lipid carrier. These models and the environmental cues that cause the cells to produce predominantly one polysaccharide over the others are subjects of current investigation.
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Structural basis for alginate secretion across the bacterial outer membrane. Proc Natl Acad Sci U S A 2011; 108:13083-8. [PMID: 21778407 DOI: 10.1073/pnas.1104984108] [Citation(s) in RCA: 71] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Pseudomonas aeruginosa is the predominant pathogen associated with chronic lung infection among cystic fibrosis patients. During colonization of the lung, P. aeruginosa converts to a mucoid phenotype characterized by the overproduction of the exopolysaccharide alginate. Secretion of newly synthesized alginate across the outer membrane is believed to occur through the outer membrane protein AlgE. Here we report the 2.3 Å crystal structure of AlgE, which reveals a monomeric 18-stranded β-barrel characterized by a highly electropositive pore constriction formed by an arginine-rich conduit that likely acts as a selectivity filter for the negatively charged alginate polymer. Interestingly, the pore constriction is occluded on either side by extracellular loop L2 and an unusually long periplasmic loop, T8. In halide efflux assays, deletion of loop T8 (ΔT8-AlgE) resulted in a threefold increase in anion flux compared to the wild-type or ΔL2-AlgE supporting the idea that AlgE forms a transport pathway through the membrane and suggesting that transport is regulated by T8. This model is further supported by in vivo experiments showing that complementation of an algE deletion mutant with ΔT8-AlgE impairs alginate production. Taken together, these studies support a mechanism for exopolysaccharide export across the outer membrane that is distinct from the Wza-mediated translocation observed in canonical capsular polysaccharide export systems.
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Sabirova JS, Becker A, Lünsdorf H, Nicaud JM, Timmis KN, Golyshin PN. Transcriptional profiling of the marine oil-degrading bacterium Alcanivorax borkumensis during growth on n-alkanes. FEMS Microbiol Lett 2011; 319:160-8. [DOI: 10.1111/j.1574-6968.2011.02279.x] [Citation(s) in RCA: 52] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022] Open
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18
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Poroyko V, White JR, Wang M, Donovan S, Alverdy J, Liu DC, Morowitz MJ. Gut microbial gene expression in mother-fed and formula-fed piglets. PLoS One 2010; 5:e12459. [PMID: 20805981 PMCID: PMC2929194 DOI: 10.1371/journal.pone.0012459] [Citation(s) in RCA: 83] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/25/2010] [Accepted: 07/21/2010] [Indexed: 02/06/2023] Open
Abstract
BACKGROUND Effects of diet on the structure and function of gut microbial communities in newborn infants are poorly understood. High-resolution molecular studies are needed to definitively ascertain whether gut microbial communities are distinct in milk-fed and formula-fed infants. METHODOLOGY/PRINCIPAL FINDINGS Pyrosequencing-based whole transcriptome shotgun sequencing (RNA-seq) was used to evaluate community wide gut microbial gene expression in 21 day old neonatal piglets fed either with sow's milk (mother fed, MF; n = 4) or with artificial formula (formula fed, FF; n = 4). Microbial DNA and RNA were harvested from cecal contents for each animal. cDNA libraries and 16S rDNA amplicons were sequenced on the Roche 454 GS-FLX Titanium system. Communities were similar at the level of phylum but were dissimilar at the level of genus; Prevotella was the dominant genus within MF samples and Bacteroides was most abundant within FF samples. Screened cDNA sequences were assigned functional annotations by the MG-RAST annotation pipeline and based upon best-BLASTX-hits to the NCBI COG database. Patterns of gene expression were very similar in MF and FF animals. All samples were enriched with transcripts encoding enzymes for carbohydrate and protein metabolism, as well as proteins involved in stress response, binding to host epithelium, and lipopolysaccharide metabolism. Carbohydrate utilization transcripts were generally similar in both groups. The abundance of enzymes involved in several pathways related to amino acid metabolism (e.g., arginine metabolism) and oxidative stress response differed in MF and FF animals. CONCLUSIONS/SIGNIFICANCE Abundant transcripts identified in this study likely contribute to a core microbial metatranscriptome in the distal intestine. Although microbial community gene expression was generally similar in the cecal contents of MF and FF neonatal piglets, several differentially abundant gene clusters were identified. Further investigations of gut microbial gene expression will contribute to a better understanding of normal and abnormal enteric microbiology in animals and humans.
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Affiliation(s)
- Valeriy Poroyko
- Department of Surgery, The University of Chicago Pritzker School of Medicine, Chicago, Illinois, United States of America
| | - James Robert White
- Center for Bioinformatics and Computational Biology, University of Maryland, College Park, Maryland, United States of America
| | - Mei Wang
- Division of Nutritional Sciences, University of Illinois, Urbana-Champaign, Illinois, United States of America
| | - Sharon Donovan
- Division of Nutritional Sciences, University of Illinois, Urbana-Champaign, Illinois, United States of America
| | - John Alverdy
- Department of Surgery, The University of Chicago Pritzker School of Medicine, Chicago, Illinois, United States of America
| | - Donald C. Liu
- Department of Surgery, The University of Chicago Pritzker School of Medicine, Chicago, Illinois, United States of America
- Department of Pediatrics, The University of Chicago Pritzker School of Medicine, Chicago, Illinois, United States of America
| | - Michael J. Morowitz
- Department of Surgery, The University of Chicago Pritzker School of Medicine, Chicago, Illinois, United States of America
- Department of Pediatrics, The University of Chicago Pritzker School of Medicine, Chicago, Illinois, United States of America
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Abstract
One of the hallmarks of bacterial survival is their ability to adapt rapidly to changing environmental conditions. Niche adaptation is a response to the signals received that are relayed, often to regulators that modulate gene expression. In the post-genomic era, DNA microarrays are used to study the dynamics of gene expression on a global scale. Numerous studies have used Pseudomonas aeruginosa--a Gram-negative environmental and opportunistic human pathogenic bacterium--as the model organism in whole-genome transcriptome analysis. This paper reviews the transcriptome studies that have led to immense advances in our understanding of the biology of this intractable human pathogen. Comparative analysis of 23 P. aeruginosa transcriptome studies has led to the identification of a unique set of genes that are signal specific and a core set that is differentially regulated. The 303 genes in the core set are involved in bacterial homeostasis, making them attractive therapeutic targets.
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Affiliation(s)
- Deepak Balasubramanian
- Department of Biological Sciences, College of Arts and Science, Florida International University, Miami, FL 33199, USA
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20
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Pseudomonas aeruginosa Inhibition of Flagellin-activated NF-kappaB and interleukin-8 by human airway epithelial cells. Infect Immun 2009; 77:2857-65. [PMID: 19451246 DOI: 10.1128/iai.01355-08] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Pseudomonas aeruginosa-induced activation of NF-kappaB and secretion of proinflammatory cytokines by airway epithelial cells require that the bacteria express flagellin. We tested whether P. aeruginosa and human airway epithelial cells secrete factors that modulated this response. Experiments were performed with both the Calu-3 cell line and primary cultures of tracheal epithelial cells. P. aeruginosa strain PAK DeltafliC (flagellin knockout) did not activate NF-kappaB or interleukin-8 (IL-8) but inhibited flagellin-activated NF-kappaB by 40 to 50% and IL-8 secretion by 20 to 25%. PAK DeltafliC also inhibited NF-kappaB induced by IL-1beta and Toll-like receptor 2 agonist Pam3CSK4. Similar inhibitions were observed with strains PAK, PAO1, and PA14. The inhibitory factor was present in conditioned medium isolated from PAK DeltafliC or Calu-3 plus PAK DeltafliC, but it was not present in conditioned medium isolated from Calu-3 cells alone or from PAK DeltafliC that had been heat treated. Inhibition by PAK DeltafliC-conditioned medium was exerted from either the apical or the basolateral side of the epithelium, was enhanced in simple Ringer's solution over that in tissue culture medium, and did not result from altered pH or depletion of glucose. The inhibitory effect of conditioned medium was abolished by boiling and appeared from filtration studies to result from effects of a factor with a molecular mass of <3 kDa. These and further studies with isogenic mutants led to the conclusion that the NF-kappaB and IL-8 response of airway epithelial cells to P. aeruginosa results from a balance of proinflammatory effects of flagellin and antiinflammatory effects of a small (<3-kDa), heat-sensitive factor(s) that is not lipopolysaccharide, C12 homoserine lactone, alginate, CIF, or exotoxin A, S, T, U, or Y.
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21
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Alginate Production: Precursor Biosynthesis, Polymerization and Secretion. ALGINATES: BIOLOGY AND APPLICATIONS 2009. [DOI: 10.1007/978-3-540-92679-5_2] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/04/2023]
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22
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Muhammadi, Ahmed N. Genetics of bacterial alginate: alginate genes distribution, organization and biosynthesis in bacteria. Curr Genomics 2007; 8:191-202. [PMID: 18645604 PMCID: PMC2435354 DOI: 10.2174/138920207780833810] [Citation(s) in RCA: 47] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/30/2007] [Revised: 02/26/2007] [Accepted: 03/21/2007] [Indexed: 11/22/2022] Open
Abstract
Bacterial alginate genes are chromosomal and fairly widespread among rRNA homology group I Pseudomonads and Azotobacter. In both genera, the genetic pathway of alginate biosynthesis is mostly similar and the identified genes are identically organized into biosynthetic, regulatory and genetic switching clusters. In spite of these similarities,still there are transcriptional and functional variations between P. aeruginosa and A. vinelandii. In P. aeruginosa all biosynthetic genes except algC transcribe in polycistronic manner under the control of algD promoter while in A. vinelandii, these are organized into many transcriptional units. Of these, algA and algC are transcribed each from two different and algD from three different promoters. Unlike P. aeruginosa, the promoters of these transcriptional units except one of algC and algD are algT-independent. Both bacterial species carry homologous algG gene for Ca(2+)-independent epimerization. But besides algG, A. vinelandii also has algE1-7 genes which encode C-5-epimerases involved in the complex steps of Ca(2+)-dependent epimerization. A hierarchy of alginate genes expression under sigma(22)(algT) control exists in P. aeruginosa where algT is required for transcription of the response regulators algB and algR, which in turn are necessary for expression of algD and its downstream biosynthetic genes. Although algTmucABCD genes cluster play similar regulatory roles in both P. aeruginosa and A. vinelandii but unlike, transcription of A. vinelandii, algR is independent of sigma(22). These differences could be due to the fact that in A. vinelandii alginate plays a role as an integrated part in desiccation-resistant cyst which is not found in P. aeruginosa.
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Affiliation(s)
| | - Nuzhat Ahmed
- Centre for Molecular Genetics, University of Karachi, Karachi-75270,
Pakistan
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23
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Pier GB. Pseudomonas aeruginosa lipopolysaccharide: a major virulence factor, initiator of inflammation and target for effective immunity. Int J Med Microbiol 2007; 297:277-95. [PMID: 17466590 PMCID: PMC1994162 DOI: 10.1016/j.ijmm.2007.03.012] [Citation(s) in RCA: 171] [Impact Index Per Article: 10.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023] Open
Abstract
Pseudomonas aeruginosa is one of the most important bacterial pathogens encountered by immunocompromised hosts and patients with cystic fibrosis (CF), and the lipopolysaccharide (LPS) elaborated by this organism is a key factor in virulence as well as both innate and acquired host responses to infection. The molecule has a fair degree of heterogeneity in its lipid A and O-antigen structure, and elaborates two different outer-core glycoforms, of which only one is ligated to the O-antigen. A close relatedness between the chemical structures and genes encoding biosynthetic enzymes has been established, with 11 major O-antigen groups identified. The lipid A can be variably penta-, hexa- or hepta-acylated, and these isoforms have differing potencies when activating host innate immunity via binding to Toll-like receptor 4 (TLR4). The O-antigen is a major target for protective immunity as evidenced by numerous animal studies, but attempts, to date, to produce a human vaccine targeting these epitopes have not been successful. Newer strategies employing live attenuated P. aeruginosa, or heterologous attenuated bacteria expressing P. aeruginosa O-antigens are potential means to solve some of the existing problems related to making a P. aeruginosa LPS-specific vaccine. Overall, there is now a large amount of information available about the genes and enzymes needed to produce the P. aeruginosa LPS, detailed chemical structures have been determined for the major O-antigens, and significant biologic and immunologic studies have been conducted to define the role of this molecule in virulence and immunity to P. aeruginosa infection.
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Affiliation(s)
- Gerald B Pier
- Channing Laboratory, Department of Medicine, Brigham and Women's Hospital, Harvard Medical School, Boston, MA 02115, USA.
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Shankar S, Ye RW, Schlictman D, Chakrabarty AM. Exopolysaccharide alginate synthesis in Pseudomonas aeruginosa: enzymology and regulation of gene expression. ADVANCES IN ENZYMOLOGY AND RELATED AREAS OF MOLECULAR BIOLOGY 2006; 70:221-55. [PMID: 8638483 DOI: 10.1002/9780470123164.ch4] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/01/2023]
Affiliation(s)
- S Shankar
- Department of Microbiology and Immunology, University of Illinois, College of Medicine, Chicago, USA
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Remminghorst U, Rehm BHA. Bacterial alginates: from biosynthesis to applications. Biotechnol Lett 2006; 28:1701-12. [PMID: 16912921 DOI: 10.1007/s10529-006-9156-x] [Citation(s) in RCA: 175] [Impact Index Per Article: 9.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/08/2006] [Accepted: 07/01/2006] [Indexed: 12/23/2022]
Abstract
Alginate is a polysaccharide belonging to the family of linear (unbranched), non-repeating copolymers, consisting of variable amounts of beta-D-mannuronic acid and its C5-epimer alpha- L-guluronic acid linked via beta-1,4-glycosidic bonds. Like DNA, alginate is a negatively charged polymer, imparting material properties ranging from viscous solutions to gel-like structures in the presence of divalent cations. Bacterial alginates are synthesized by only two bacterial genera, Pseudomonas and Azotobacter, and have been extensively studied over the last 40 years. While primarily synthesized in form of polymannuronic acid, alginate undergoes chemical modifications comprising acetylation and epimerization, which occurs during periplasmic transfer and before final export through the outer membrane. Alginate with its unique material properties and characteristics has been increasingly considered as biomaterial for medical applications. The genetic modification of alginate producing microorganisms could enable biotechnological production of new alginates with unique, tailor-made properties, suitable for medical and industrial applications.
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Affiliation(s)
- Uwe Remminghorst
- Institute of Molecular BioSciences, Massey University, Private Bag 11222, Palmerston North, New Zealand
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26
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Remminghorst U, Rehm BHA. In vitro alginate polymerization and the functional role of Alg8 in alginate production by Pseudomonas aeruginosa. Appl Environ Microbiol 2006; 72:298-305. [PMID: 16391057 PMCID: PMC1352289 DOI: 10.1128/aem.72.1.298-305.2006] [Citation(s) in RCA: 71] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
An enzymatic in vitro alginate polymerization assay was developed by using 14C-labeled GDP-mannuronic acid as a substrate and subcellular fractions of alginate overproducing Pseudomonas aeruginosa FRD1 as a polymerase source. The highest specific alginate polymerase activity was detected in the envelope fraction, suggesting that cytoplasmic and outer membrane proteins constitute the functional alginate polymerase complex. Accordingly, no alginate polymerase activity was detected using cytoplasmic membrane or outer membrane proteins, respectively. To determine the requirement of Alg8, which has been proposed as catalytic subunit of alginate polymerase, nonpolar isogenic alg8 knockout mutants of alginate-overproducing P. aeruginosa FRD1 and P. aeruginosa PDO300 were constructed, respectively. These mutants were deficient in alginate biosynthesis, and alginate production was restored by introducing only the alg8 gene. Surprisingly, this resulted in significant alginate overproduction of the complemented P. aeruginosa Deltaalg8 mutants compared to nonmutated strains, suggesting that Alg8 is the bottleneck in alginate biosynthesis. (1)H-NMR analysis of alginate isolated from these complemented mutants showed that the degree of acetylation increased from 4.7 to 9.3% and the guluronic acid content was reduced from 38 to 19%. Protein topology prediction indicated that Alg8 is a membrane protein. Fusion protein analysis provided evidence that Alg8 is located in the cytoplasmic membrane with a periplasmic C terminus. Subcellular fractionation suggested that the highest specific PhoA activity of Alg8-PhoA is present in the cytoplasmic membrane. A structural model of Alg8 based on the structure of SpsA from Bacillus subtilis was developed.
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Affiliation(s)
- Uwe Remminghorst
- Institute of Molecular BioSciences, Massey University, Private Bag 11222, Palmerston North, New Zealand
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27
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McCarthy TR, Torrelles JB, MacFarlane AS, Katawczik M, Kutzbach B, Desjardin LE, Clegg S, Goldberg JB, Schlesinger LS. Overexpression of Mycobacterium tuberculosis manB, a phosphomannomutase that increases phosphatidylinositol mannoside biosynthesis in Mycobacterium smegmatis and mycobacterial association with human macrophages. Mol Microbiol 2006; 58:774-90. [PMID: 16238626 DOI: 10.1111/j.1365-2958.2005.04862.x] [Citation(s) in RCA: 44] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
Mycobacterium tuberculosis (M. tb) pathogenesis involves the interaction between the mycobacterial cell envelope and host macrophage, a process mediated, in part, by binding of the mannose caps of M. tb lipoarabinomannan (ManLAM) to the macrophage mannose receptor (MR). A presumed critical step in the biosynthesis of ManLAM, and other mannose-containing glycoconjugates, is the conversion of mannose-6-phosphate to mannose-1-phosphate, by a phosphomannomutase (PMM), to produce GDP-mannose, the primary mannose-donor in mycobacteria. We have identified four M. tb H37Rv genes with similarity to known PMMs. Using in vivo complementation of PMM and phosphoglucomutase (PGM) deficient strains of Pseudomonas aeruginosa, and an in vitro enzyme assay, we have identified both PMM and PGM activity from one of these genes, Rv3257c (MtmanB). MtmanB overexpression in M. smegmatis produced increased levels of LAM, lipomannan, and phosphatidylinositol mannosides (PIMs) compared with control strains and led to a 13.3 +/- 3.9-fold greater association of mycobacteria with human macrophages, in a mannan-inhibitable fashion. This increased association was mediated by the overproduction of higher order PIMs that possess mannose cap structures. We conclude that MtmanB encodes a functional PMM involved in the biosynthesis of mannosylated lipoglycans that participate in the association of mycobacteria with macrophage phagocytic receptors.
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Affiliation(s)
- Travis R McCarthy
- Department of Medicine and Molecular Virology, the Center for Microbial Interface Biology, and the Division of Infectious Diseases, The Ohio State University, Columbus, OH 43210, USA
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Albrecht MT, Schiller NL. Alginate lyase (AlgL) activity is required for alginate biosynthesis in Pseudomonas aeruginosa. J Bacteriol 2005; 187:3869-72. [PMID: 15901714 PMCID: PMC1112040 DOI: 10.1128/jb.187.11.3869-3872.2005] [Citation(s) in RCA: 43] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
To determine whether AlgL's lyase activity is required for alginate production in Pseudomonas aeruginosa, an algLdelta::Gm(r) mutant (FRD-MA7) was created. algL complementation of FRD-MA7 restored alginate production, but algL constructs containing mutations inactivating lyase activity did not, demonstrating that the enzymatic activity of AlgL is required for alginate production.
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Affiliation(s)
- Mark T Albrecht
- Division of Biomedical Sciences, University of California, Riverside, Riverside, California 92521-0121, USA
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29
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Robles-Price A, Wong TY, Sletta H, Valla S, Schiller NL. AlgX is a periplasmic protein required for alginate biosynthesis in Pseudomonas aeruginosa. J Bacteriol 2004; 186:7369-77. [PMID: 15489449 PMCID: PMC523204 DOI: 10.1128/jb.186.21.7369-7377.2004] [Citation(s) in RCA: 61] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Alginate, an exopolysaccharide produced by Pseudomonas aeruginosa, provides the bacterium with a selective advantage that makes it difficult to eradicate from the lungs of cystic fibrosis (CF) patients. Previous studies identified a gene, algX, within the alginate biosynthetic gene cluster on the P. aeruginosa chromosome. By probing cell fractions with anti-AlgX antibodies in a Western blot, AlgX was localized within the periplasm. Consistent with these results is the presence of a 26-amino-acid signal sequence. To examine the requirement for AlgX in alginate biosynthesis, part of algX in P. aeruginosa strain FRD1::pJLS3 was replaced with a nonpolar gentamicin resistance cassette. The resulting algXDelta::Gm mutant was verified by PCR and Western blot analysis and was phenotypically nonmucoid (non-alginate producing). The algXDelta::Gm mutant was restored to the mucoid phenotype with wild-type P. aeruginosa algX provided on a plasmid. The algXDelta::Gm mutant was found to secrete dialyzable oligouronic acids of various lengths. Mass spectroscopy and Dionex chromatography indicated that the dialyzable uronic acids are mainly mannuronic acid dimers resulting from alginate lyase (AlgL) degradation of polymannuronic acid. These studies suggest that AlgX is part of a protein scaffold that surrounds and protects newly formed polymers from AlgL degradation as they are transported within the periplasm for further modification and eventual transport out of the cell.
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Affiliation(s)
- Antonette Robles-Price
- Division of Biomedical Sciences, University of California, Riverside, CA 92521-0121, USA
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30
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Gaona G, Núñez C, Goldberg JB, Linford AS, Nájera R, Castañeda M, Guzmán J, EspÃn G, Soberón-Chávez G. Characterization of the Azotobacter vinelandii algCgene involved in alginate and lipopolysaccharide production. FEMS Microbiol Lett 2004. [DOI: 10.1111/j.1574-6968.2004.tb09756.x] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022] Open
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Stapper AP, Narasimhan G, Ohman DE, Barakat J, Hentzer M, Molin S, Kharazmi A, Høiby N, Mathee K. Alginate production affects Pseudomonas aeruginosa biofilm development and architecture, but is not essential for biofilm formation. J Med Microbiol 2004; 53:679-690. [PMID: 15184541 DOI: 10.1099/jmm.0.45539-0] [Citation(s) in RCA: 116] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Extracellular polymers can facilitate the non-specific attachment of bacteria to surfaces and hold together developing biofilms. This study was undertaken to qualitatively and quantitatively compare the architecture of biofilms produced byPseudomonas aeruginosastrain PAO1 and its alginate-overproducing (mucA22) and alginate-defective (algD) variants in order to discern the role of alginate in biofilm formation. These strains, PAO1, Alg+PAOmucA22and Alg−PAOalgD, tagged with green fluorescent protein, were grown in a continuous flow cell system to characterize the developmental cycles of their biofilm formation using confocal laser scanning microscopy. Biofilm Image Processing (bip) and Community Statistics (comstat) software programs were used to provide quantitative measurements of the two-dimensional biofilm images. All three strains formed distinguishable biofilm architectures, indicating that the production of alginate is not critical for biofilm formation. Observation over a period of 5 days indicated a three-stage development pattern consisting of initiation, establishment and maturation. Furthermore, this study showed that phenotypically distinguishable biofilms can be quantitatively differentiated.
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Affiliation(s)
- Andres Plata Stapper
- Department of Biological Sciences1 and School of Computer Science2, Florida International University, Miami, FL 33199, USA 3Department of Microbiology and Immunology, Virginia Commonwealth University, Richmond, VA 23298, USA 4Section of Molecular Microbiology, The Technical University of Denmark, DK-2800 Lyngby, Denmark 5Department of Clinical Microbiology, University Hospital of Copenhagen, DK-2100 Copenhagen, Denmark
| | - Giri Narasimhan
- Department of Biological Sciences1 and School of Computer Science2, Florida International University, Miami, FL 33199, USA 3Department of Microbiology and Immunology, Virginia Commonwealth University, Richmond, VA 23298, USA 4Section of Molecular Microbiology, The Technical University of Denmark, DK-2800 Lyngby, Denmark 5Department of Clinical Microbiology, University Hospital of Copenhagen, DK-2100 Copenhagen, Denmark
| | - Dennis E Ohman
- Department of Biological Sciences1 and School of Computer Science2, Florida International University, Miami, FL 33199, USA 3Department of Microbiology and Immunology, Virginia Commonwealth University, Richmond, VA 23298, USA 4Section of Molecular Microbiology, The Technical University of Denmark, DK-2800 Lyngby, Denmark 5Department of Clinical Microbiology, University Hospital of Copenhagen, DK-2100 Copenhagen, Denmark
| | - Johnny Barakat
- Department of Biological Sciences1 and School of Computer Science2, Florida International University, Miami, FL 33199, USA 3Department of Microbiology and Immunology, Virginia Commonwealth University, Richmond, VA 23298, USA 4Section of Molecular Microbiology, The Technical University of Denmark, DK-2800 Lyngby, Denmark 5Department of Clinical Microbiology, University Hospital of Copenhagen, DK-2100 Copenhagen, Denmark
| | - Morten Hentzer
- Department of Biological Sciences1 and School of Computer Science2, Florida International University, Miami, FL 33199, USA 3Department of Microbiology and Immunology, Virginia Commonwealth University, Richmond, VA 23298, USA 4Section of Molecular Microbiology, The Technical University of Denmark, DK-2800 Lyngby, Denmark 5Department of Clinical Microbiology, University Hospital of Copenhagen, DK-2100 Copenhagen, Denmark
| | - Søren Molin
- Department of Biological Sciences1 and School of Computer Science2, Florida International University, Miami, FL 33199, USA 3Department of Microbiology and Immunology, Virginia Commonwealth University, Richmond, VA 23298, USA 4Section of Molecular Microbiology, The Technical University of Denmark, DK-2800 Lyngby, Denmark 5Department of Clinical Microbiology, University Hospital of Copenhagen, DK-2100 Copenhagen, Denmark
| | - Arsalan Kharazmi
- Department of Biological Sciences1 and School of Computer Science2, Florida International University, Miami, FL 33199, USA 3Department of Microbiology and Immunology, Virginia Commonwealth University, Richmond, VA 23298, USA 4Section of Molecular Microbiology, The Technical University of Denmark, DK-2800 Lyngby, Denmark 5Department of Clinical Microbiology, University Hospital of Copenhagen, DK-2100 Copenhagen, Denmark
| | - Niels Høiby
- Department of Biological Sciences1 and School of Computer Science2, Florida International University, Miami, FL 33199, USA 3Department of Microbiology and Immunology, Virginia Commonwealth University, Richmond, VA 23298, USA 4Section of Molecular Microbiology, The Technical University of Denmark, DK-2800 Lyngby, Denmark 5Department of Clinical Microbiology, University Hospital of Copenhagen, DK-2100 Copenhagen, Denmark
| | - Kalai Mathee
- Department of Biological Sciences1 and School of Computer Science2, Florida International University, Miami, FL 33199, USA 3Department of Microbiology and Immunology, Virginia Commonwealth University, Richmond, VA 23298, USA 4Section of Molecular Microbiology, The Technical University of Denmark, DK-2800 Lyngby, Denmark 5Department of Clinical Microbiology, University Hospital of Copenhagen, DK-2100 Copenhagen, Denmark
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Kooistra O, Bedoux G, Brecker L, Lindner B, Sánchez Carballo P, Haras D, Zähringer U. Structure of a highly phosphorylated lipopolysaccharide core in the ΔalgC mutants derived from Pseudomonas aeruginosa wild-type strains PAO1 (serogroup O5) and PAC1R (serogroup O3). Carbohydr Res 2003; 338:2667-77. [PMID: 14670725 DOI: 10.1016/j.carres.2003.07.004] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
Abstract
Lipopolysaccharides (LPS) were isolated from rough-type mutant strains of Pseudomonas aeruginosa (Delta algC) derived from wild-type strains PAO1 (serogroup O5) and PAC1R (serogroup O3). Structural studies of the LPS core region with a special focus on the phosphorylation pattern were performed by 2D NMR spectroscopy, including a 1H,(31)P HMQC-TOCSY experiment, MALDI-TOF MS, and Fourier-transform ion cyclotron resonance ESIMS using the capillary skimmer dissociation technique. Both LPS were found to contain two residues each of 3-deoxy-D-manno-oct-2-ulosonic acid (Kdo) and L-glycero-D-manno-heptose (Hep), one residue of N-(L-alanyl)-D-galactosamine and one O-carbamoyl group (Cm) on the distal Hep residue. The following structures of a tetrasaccharide trisphosphate from strain PAC1R Delta algC and that carrying an additional ethanolamine phosphate group (PEtN) from strain PAO1 Delta algC were elucidated: [carbohydrate structre: see text] where R=P in PAC1R Delta algC and PPEtN in PAO1 Delta algC. To our knowledge, in this work the presence of ethanolamine diphosphate is unambiguously confirmed and its position established for the first time in the LPS core of a rough-type strain of P. aeruginosa. In addition, the structure of the complete LPS core of wild-type strain P. aeruginosa PAO1 was reinvestigated and the position of the phosphorylation sites was revised.
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Affiliation(s)
- Oliver Kooistra
- Division of Immunochemistry, Research Center, Borstel, Leibniz Center for Medicine and Biosciences, D-23845 Borstel, Germany
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Jain S, Franklin MJ, Ertesvåg H, Valla S, Ohman DE. The dual roles of AlgG in C-5-epimerization and secretion of alginate polymers in Pseudomonas aeruginosa. Mol Microbiol 2003; 47:1123-33. [PMID: 12581364 DOI: 10.1046/j.1365-2958.2003.03361.x] [Citation(s) in RCA: 57] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Pseudomonas aeruginosa strains causing chronic pulmonary infections in cystic fibrosis patients produce high levels of alginate, an exopolysaccharide that confers a mucoid phenotype. Alginate is a linear polymer of d-mannuronate (M) and variable amounts of its C-5-epimer, l-guluronate (G). AlgG is a periplasmic C-5-epimerase that converts poly d-mannuronate to the mixed M+G sequence of alginate. To understand better the role and mechanism of AlgG activity, a mutant was constructed in the mucoid strain FRD1 with a defined non-polar deletion of algG. Instead of producing poly mannuronate, the algG deletion mutant secreted dialysable uronic acids, as does a mutant lacking the periplasmic protein AlgK. High levels of unsaturated ends and the nuclear magnetic resonance spectroscopy pattern revealed that the small, secreted uronic acids were the products of extensive polymer digestion by AlgL, a periplasmic alginate lyase co-expressed with AlgG and AlgK. Thus, AlgG is bifunctional with (i) epimerase activity and (ii) a role in protecting alginate from degradation by AlgL during transport through the periplasm. AlgK appears to share the second role. AlgG and AlgK may be part of a periplasmic protein complex, or scaffold, that guides alginate polymers to the outer membrane secretin (AlgE). To characterize the epimerase activity of AlgG further, the algG4 allele of poly mannuronate-producing FRD462 was shown to encode a protein lacking only the epimerase function. The sequence of algG4 has a Ser-272 to Asn substitution in a serine-threonine-rich and conserved region of AlgG, which revealed a critical residue for C-5-epimerase activity.
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Affiliation(s)
- Sumita Jain
- Department of Microbiology, Medical College of Virginia Campus of Virginia Commonwealth University, 1101 E. Marshall St., Rm. 5-051, Richmond, VA 23298-0678, USA
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Evans D, Kuo T, Kwong M, Van R, Fleiszig S. Pseudomonas aeruginosa strains with lipopolysaccharide defects exhibit reduced intracellular viability after invasion of corneal epithelial cells. Exp Eye Res 2002; 75:635-43. [PMID: 12470965 DOI: 10.1006/exer.2002.2072] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Pseudomonas aeruginosa is a leading cause of infectious keratitis. Many ocular isolates of this bacterium invade corneal epithelial cells in vitro and in vivo. Antibiotic survival assays have shown that a complete core lipopolysaccharide is required for full epithelial invasion by P. aeruginosa. In this study, we show that P. aeruginosa mutants with defects in their lipopolysaccharide core and O antigen exhibited reduced viability after internalization by corneal epithelial cells. Restoration of lipopolysaccharide core and O antigen expression by complementation with the plasmid pLPS1 restored intracellular survival. P. aeruginosa strains with a complete lipopolysaccharide survived and replicated within the cells. The data suggest that lipopolysaccharide is involved in the intracellular survival and/or replication of P. aeruginosa, indicating an additional mechanism by which this important virulence factor may contribute to the pathogenesis of corneal infection.
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Affiliation(s)
- David Evans
- Morton D. Sarver Laboratory for Cornea and Contact Lens Research, School of Optometry, University of California at Berkeley, Berkeley, CA 94720, USA
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Franklin MJ, Ohman DE. Mutant analysis and cellular localization of the AlgI, AlgJ, and AlgF proteins required for O acetylation of alginate in Pseudomonas aeruginosa. J Bacteriol 2002; 184:3000-7. [PMID: 12003941 PMCID: PMC135050 DOI: 10.1128/jb.184.11.3000-3007.2002] [Citation(s) in RCA: 77] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/04/2001] [Accepted: 02/27/2002] [Indexed: 11/20/2022] Open
Abstract
Alginate is an extracellular polysaccharide produced by mucoid strains of Pseudomonas aeruginosa that are typically isolated from the pulmonary tracts of chronically infected cystic fibrosis patients. Alginate is a linear polymer of D-mannuronate and L-guluronate with O-acetyl ester linkages on the O-2 and/or O-3 position of the mannuronate residues. The presence of O-acetyl groups plays an important role in the ability of the polymer to act as a virulence factor, and the algF, algJ, and algI genes are known to be essential for the addition of O-acetyl groups to alginate. To better understand the mechanism of O acetylation of alginate, the cellular locations of the AlgI, AlgJ, and AlgF proteins were determined. For these studies, defined nonpolar algI, algJ, and algF deletion mutants of P. aeruginosa strain FRD1 were constructed, and each mutant produced alginate lacking O-acetyl groups. Expression of algI, algJ, or algF in trans in the corresponding mutant complemented each O acetylation defect. Random phoA (alkaline phosphatase [AP] gene) fusions to algF, algJ, and algI were constructed. All in-frame fusions to algF and algJ had AP activity, indicating that both AlgF and AlgJ were exported to the periplasm. Immunoblot analysis of spheroplasts and periplasmic fractions showed that AlgF was released with the periplasmic contents but that AlgJ remained with the spheroplast fraction. An N-terminal sequence analysis of AlgJ showed that its putative AlgJ signal peptide was not cleaved, suggesting that AlgJ is anchored to the cytoplasmic membrane by its uncleaved signal peptide. AP gene fusions were also used to map the membrane topology of AlgI, and the results suggest that it is an integral membrane protein with seven transmembrane domains. These results suggest that AlgI-AlgJ-AlgF may form a complex in the membrane that is the reaction center for O acetylation of alginate.
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Affiliation(s)
- Michael J Franklin
- Department of Microbiology and Center for Biofilm Engineering, Montana State University, Bozeman, Montana, USA
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Naught LE, Tipton PA. Kinetic mechanism and pH dependence of the kinetic parameters of Pseudomonas aeruginosa phosphomannomutase/phosphoglucomutase. Arch Biochem Biophys 2001; 396:111-8. [PMID: 11716469 DOI: 10.1006/abbi.2001.2618] [Citation(s) in RCA: 47] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The enzyme phosphomannomutase/phosphoglucomutase (PMM/PGM) is responsible for the formation of mannose 1-phosphate and glucose 1-phosphate in the human pathogenic bacterium Pseudomonas aeruginosa. Mannose 1-phosphate and glucose 1-phosphate are required for the biosynthesis of polysaccharides that contribute to the virulence of P. aeruginosa, so inhibitors of PMM/PGM may lead to clinically useful compounds. The V/K values for mannose 6-phosphate and glucose 6-phosphate show that they are equally good substrates for the enzyme. PMM/PGM overexpressed in Escherichia coli is isolated as a phosphoenzyme; surprisingly, mutation of serine 108 where phosphorylation occurs results in phosphorylation of a different residue so that activity is reduced only 20-fold from that of wild-type enzyme. In the reverse reaction glucose 1-phosphate exhibits substrate inhibition, which arises through its competition with the activator glucose 1,6-bisphosphate for binding to dephosphoenzyme. This phenomenon is consistent with a mechanism in which the enzyme phosphorylates the substrate to generate a bisphosphorylated intermediate that reorients in the active site to return its original phosphoryl group to the enzyme and generate the observed product. The pH dependence of the kinetic parameters suggests that the active site contains a residue that serves as a general base in the catalytic reaction and one that acts as a general acid. However, the pK of the general acid is 7.4 and that of the general base is 8.4 so these residues exist in a state of reverse protonation in the active enzyme.
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Affiliation(s)
- L E Naught
- Department of Biochemistry, University of Missouri, 117 Schweitzer Hall, Columbia, Missouri 65211, USA
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Michel G, Ball G, Goldberg JB, Lazdunski A. Alteration of the lipopolysaccharide structure affects the functioning of the Xcp secretory system in Pseudomonas aeruginosa. J Bacteriol 2000; 182:696-703. [PMID: 10633103 PMCID: PMC94332 DOI: 10.1128/jb.182.3.696-703.2000] [Citation(s) in RCA: 21] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Pseudomonas aeruginosa secretes a wide range of hydrolytic enzymes into the external medium by the Xcp secretion machinery. To better understand the role played by envelope constituents in the functioning of this type II secretory system, we have studied the influence of lipopolysaccharide (LPS) on the secretion of two extracellular enzymes, the elastase LasB and the lipase LipA. Strains with defective LPS decreased production of LasB and altered the secretion processes of both LasB and LipA without any apparent effect on the composition of the Xcp machinery. The PAO1algC strain, defective in the outer core of LPS, was leaky, as shown by the extracellular release of the periplasmic beta-lactamase. Generation of an xcpR mutation in this mutant led only to a partial accumulation of LasB within the cells, indicating that in strain PAO1algC with a functional xcpR gene, LasB was released in the extracellular medium partly by leakage and partly by secretion. The pool of LasB released into the medium by leakage was not recovered in an active form, while extracellular LasB was active when secreted via the secretory machinery. Further analysis revealed that the presence of a functional Xcp machinery is strictly required for the activation process of LasB. Our results provide evidence that the Xcp system is not fully functional when the LPS structure of P. aeruginosa is altered.
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Affiliation(s)
- G Michel
- Laboratoire d'Ingénierie des Systèmes Macromoléculaires, CNRS, 13402 Marseille Cedex 20, France.
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Gerçeker AA, Zaidi T, Marks P, Golan DE, Pier GB. Impact of heterogeneity within cultured cells on bacterial invasion: analysis of Pseudomonas aeruginosa and Salmonella enterica serovar typhi entry into MDCK cells by using a green fluorescent protein-labelled cystic fibrosis transmembrane conductance regulator receptor. Infect Immun 2000; 68:861-70. [PMID: 10639456 PMCID: PMC97215 DOI: 10.1128/iai.68.2.861-870.2000] [Citation(s) in RCA: 21] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The cystic fibrosis transmembrane conductance regulator (CFTR) is a chloride ion channel that also serves as a receptor for entry of Pseudomonas aeruginosa and Salmonella enterica serovar Typhi into epithelial cells. To evaluate heterogeneity in CFTR protein expression in cultured cells and the effect of heterogeneity on internalization of different P. aeruginosa and serovar Typhi strains, we used two-color flow cytometry and confocal laser microscopy to study bacterial uptake by Madin-Darby canine kidney (MDCK) type I epithelial cells stably expressing a green fluorescent protein (GFP)-CFTR fusion construct (MDCK-GFP-CFTR cells). We found a strong correlation between cell size and GFP-CFTR protein expression, with 60 to 70% of cells expressing low levels of GFP-CFTR protein, 20 to 30% expressing intermediate levels, and <10% expressing high levels. The cells were sorted into low-, intermediate-, or high-level producers of CFTR protein; in vitro growth of each sorted population yielded the same distribution of CFTR protein expression as that in the original population. Cells expressing either low or high levels of CFTR protein internalized bacteria poorly; maximal bacterial uptake occurred in the cells expressing intermediate levels of CFTR protein. Treatment of MDCK cells with sodium butyrate markedly enhanced the production of CFTR protein without increasing cell size; butyrate treatment also increased the proportion of cells with internalized bacteria. However, there were fewer bacteria per butyrate-treated cell and, for P. aeruginosa, there was an overall decrease in the total level of bacterial uptake. The most highly ingested bacterial strains were internalized by fewer total MDCK-GFP-CFTR cells, indicating preferential bacterial uptake by a minority of epithelial cells within a given culture. Confocal fluorescence microscopy showed that P. aeruginosa and serovar Typhi induced cytoplasmic accumulation of CFTR protein close to the plasma membrane where the bacteria were adherent. These results show that within a population of MDCK-GFP-CFTR cells, there are cells with markedly different abilities to ingest bacteria via CFTR, the majority of the P. aeruginosa and serovar Typhi cells are ingested by the one-fourth to one-third of the cells that exhibit an intermediate size and level of CFTR protein expression, and overexpression of the CFTR receptor does not increase total bacterial uptake but rather allows more epithelial cells to ingest fewer total bacteria.
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Affiliation(s)
- A A Gerçeker
- Channing Laboratory, Brigham and Women's Hospital, and Department of Biological Chemistry and Molecular Pharmacology, Harvard Medical School, Boston, Massachusetts 02115, USA
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McNAMARA NA, Van R, Tuchin OS, Fleiszig SM. Ocular surface epithelia express mRNA for human beta defensin-2. Exp Eye Res 1999; 69:483-90. [PMID: 10548468 DOI: 10.1006/exer.1999.0722] [Citation(s) in RCA: 92] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Human skin, lung and trachea produce human beta defensin-2 (hBD-2), an inducible, transcriptionally regulated antibiotic peptide with activity against gram negative bacteria, which may explain the unusual resistance of these tissues to infection. Since an intact corneal epithelium is also highly resistant to infection, we examined whether human ocular surface epithelia might produce hBD-2. Conjunctival epithelial cells were obtained from a human cadaver eye, while corneal epithelial cells were obtained from both a cadaver eye and the eye of a living human patient. Using reverse transcription-polymerase chain reaction and custom primers for hBD-2, a 257 bp sequence was amplified from both human corneal and conjunctival epithelial cell cDNA, and the amino acid sequence of this DNA band was computer-matched with the known gene sequence of hBD-2 available through GenBank (Z71389). To determine whether bacterial by-products upregulate hBD-2 mRNA expression, we stimulated confluent SV 40-immortalized human corneal epithelial cells with bacterial culture supernatant prepared from either wild-type P. aeruginosa strain PAO1 or two different lipopolysaccharide (LPS) mutants of PAO1. Both of these mutants, strains AK1012 and PAO1 algC::tet, are deficient in phosphomannomutase activity which is required for the synthesis of both a complete polysaccharide core and the O side chain structures of the LPS molecule. Neither of these mutations affects the lipid A portion of LPS. Cells treated with P. aeruginosa wild-type PAO1 bacterial culture supernatant demonstrated strong upregulation of hBD-2 mRNA expression, whereas cells stimulated with culture supernatant produced by either of the LPS mutants showed little or no change in hBD-2 gene expression. LPS extracted from the bacterial culture supernatant was used to demonstrate that upregulation of hBD-2 is caused by LPS. Genistein blocked this upregulation suggesting that protein tyrosine kinase activity is involved. Thus, both human corneal and conjunctival epithelium express mRNA for hBD-2, and this expression is upregulated by bacterial LPS. Data obtained from LPS mutants suggest that lipid A, which is responsible for initiating a number of the pathophysiological manifestations induced by endotoxin in mammals, is not required. Stimulation of endogenous hBD-2 production via the active portion of LPS might have therapeutic potential.
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Affiliation(s)
- N A McNAMARA
- Morton D. Sarver Laboratory for Cornea and Contact Lens Research, School of Optometry, University of California, Berkeley, CA, USA
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Dean CR, Franklund CV, Retief JD, Coyne MJ, Hatano K, Evans DJ, Pier GB, Goldberg JB. Characterization of the serogroup O11 O-antigen locus of Pseudomonas aeruginosa PA103. J Bacteriol 1999; 181:4275-84. [PMID: 10400585 PMCID: PMC93929 DOI: 10.1128/jb.181.14.4275-4284.1999] [Citation(s) in RCA: 62] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
We previously cloned a genomic DNA fragment from the serogroup O11 Pseudomonas aeruginosa strain PA103 that contained all genes necessary for O-antigen synthesis and directed the expression of serogroup O11 antigen on recombinant Escherichia coli and Salmonella. To elucidate the pathway of serogroup O11 antigen synthesis, the nucleotide sequence of the biosynthetic genes was determined. Eleven open reading frames likely to be involved in serogroup O11 O-antigen biosynthesis were identified and are designated in order as wzzPaO111 (wzz from P. aeruginosa serogroup O11), wzxPaO11, wbjA, wzyPaO11, wbjB to wbjF, wbpLO11 and wbpMO11 (wbpL and wbpM from serogroup O11). Consistent with previous descriptions of O-antigen biosynthetic gene loci, the entire region with the exception of wbpMO11 has a markedly reduced G+C content relative to the chromosomal average. WzyPaO11 shows no significant similarity at the protein or DNA sequence level to any database sequence and is very hydrophobic, with 10 to 12 putative transmembrane domains, both typical characteristics of O-antigen polymerases. A nonpolar chromosomal insertion mutation in wzyPaO11 in P. aeruginosa PA103 confirmed the identity of this gene. There is striking similarity between WbjBCDE and Cap(5/8)EFGL, involved in type 5 and type 8 capsule biosynthesis in Staphylococcus aureus. There is nearly total identity between wbpMO11 and wbpMO5, previously shown by others to be present in all 20 P. aeruginosa serogroups. Using similarity searches, we have assigned functions to the proteins encoded by the PA103 O-antigen locus and present the potential steps in the pathway for the biosynthesis of P. aeruginosa serogroup O11 O antigen.
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Affiliation(s)
- C R Dean
- Departments of Microbiology, University of Virginia Health Sciences Center, Charlottesville, Virginia 22908, USA
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41
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Gacesa P. Bacterial alginate biosynthesis--recent progress and future prospects. MICROBIOLOGY (READING, ENGLAND) 1998; 144 ( Pt 5):1133-1143. [PMID: 9611788 DOI: 10.1099/00221287-144-5-1133] [Citation(s) in RCA: 137] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
The extracellular polysaccharide alginate has been widely associated with chronic Pseudomonas aeruginosa infections in the cystic fibrosis lung. However, it is clear that alginate biosynthesis is a more widespread phenomenon. Alginate plays a key role as a virulence factor of plant-pathogenic pseudomonads, in the formation of biofilms and with the encystment process of Azotobacter spp.
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Affiliation(s)
- Peter Gacesa
- Faculty of Science and Engineering, Manchester Metropolitan University, John Dalton Extension, Chester Street, Manchester M1 5GD, UK
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42
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Allen CA, Adams LG, Ficht TA. Transposon-derived Brucella abortus rough mutants are attenuated and exhibit reduced intracellular survival. Infect Immun 1998; 66:1008-16. [PMID: 9488389 PMCID: PMC108009 DOI: 10.1128/iai.66.3.1008-1016.1998] [Citation(s) in RCA: 140] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/25/1997] [Accepted: 12/19/1997] [Indexed: 02/06/2023] Open
Abstract
The O antigen of Brucella abortus has been described as a major virulence determinant based on the attenuated survival of fortuitously isolated rough variants. However, the lack of genetic definition of these mutants and the virulence of naturally occurring rough species, Brucella ovis and Brucella canis, has confused interpretation. To better characterize the role of O antigen in virulence and survival, transposon mutagenesis was used to generate B. abortus rough mutants defective in O-antigen presentation. Sequence analysis of DNA flanking the site of Tn5 insertion was used to verify insertion in genes encoding lipopolysaccharide (LPS) biosynthetic functions. Not surprisingly, each of the rough mutants was attenuated for survival in mice, but unexpected differences among the mutants were observed. In an effort to define the basis for the observed differences, the structure of the rough LPS and the sensitivity of these mutants to individual killing mechanisms were examined in vitro. All of the B. abortus rough mutants exhibited a 4- to 5-log-unit increase, compared to the smooth parental strain, in sensitivity to complement-mediated lysis. Little change was evident in the sensitivity of these organisms to hydrogen peroxide, consistent with an inability of O antigen to exclude relatively small molecules. Sensitivity to polymyxin B, which was employed as a model cationic, amphipathic peptide similar to defensins found in phagocytic cells, revealed survival differences among the rough mutants similar to those observed in the mouse. One mutant in particular exhibited hypersensitivity to polymyxin B and reduced survival in mice. This mutant was characterized by a truncated rough LPS. DNA sequence analysis of this mutant revealed a transposon interruption in the gene encoding phosphomannomutase (pmm), suggesting that this activity may be required for the synthesis of a full-length core polysaccharide in addition to O antigen. B. abortus O antigen appears to be essential for extra- and intracellular survival in mice.
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Affiliation(s)
- C A Allen
- Department of Veterinary Pathobiology, Texas A&M University, College Station 77843-4467, USA
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Jain S, Ohman DE. Deletion of algK in mucoid Pseudomonas aeruginosa blocks alginate polymer formation and results in uronic acid secretion. J Bacteriol 1998; 180:634-41. [PMID: 9457868 PMCID: PMC106932 DOI: 10.1128/jb.180.3.634-641.1998] [Citation(s) in RCA: 60] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/17/1997] [Accepted: 11/19/1997] [Indexed: 02/06/2023] Open
Abstract
Chronic pulmonary infection with Pseudomonas aeruginosa is a common and serious problem in patients with cystic fibrosis (CF). The P. aeruginosa isolates from these patients typically have a mucoid colony morphology due to overproduction of the exopolysaccharide alginate, which contributes to the persistence of the organisms in the CF lung. Most of the alginate biosynthetic genes are clustered in the algD operon, located at 34 min on the chromosome. Alginate biosynthesis begins with the formation of an activated monomer, GDP-mannuronate, which is known to occur via the products of the algA, algC, and algD genes. Polymannuronate forms in the periplasm, but the gene products involved in mannuronate translocation across the inner membrane and its polymerization are not known. One locus of the operon which remained uncharacterized was a new gene called algK between alg44 and algE. We sequenced algK from the mucoid CF isolate FRD1 and expressed it in Escherichia coli, which revealed a polypeptide of the predicted size (52 kDa). The sequence of AlgK showed an apparent signal peptide characteristic of a lipoprotein. AlgK-PhoA fusion proteins were constructed and shown to be active, indicating that AlgK has a periplasmic subcellular localization. To test the phenotype of an AlgK-mutant, the algK coding sequence was replaced with a nonpolar gentamicin resistance cassette to avoid polar effects on genes downstream of algK that are essential for polymer formation. The algKdelta mutant was nonmucoid, demonstrating that AlgK was required for alginate production. Also, AlgK- mutants demonstrated a small-colony phenotype on L agar, suggesting that the loss of AlgK also caused a growth defect. The mutant phenotypes were complemented by a plasmid expressing algK in trans. When the algKdelta mutation was placed in an algJ::Tn501 background, where algA was not expressed due to polar transposon effects, the growth defect was not observed. AlgK- mutants appeared to accumulate a toxic extracellular product, and we hypothesized that this could be an unpolymerized alginate precursor. High levels of low-molecular-weight uronic acid were produced by the AlgK- mutant. When AlgK- culture supernatants were subjected to dialysis, high levels of uronic acids diffused out of the dialysis sac, and no uronic acids were detectable after extensive dialysis. In contrast, the mucoid wild-type strain produced only polymerized uronic acids (i.e., alginate), whereas the algKdelta algJ::Tn501 mutant produced no uronic acids. Thus, the alginate pathway in an AlgK- mutant was blocked after transport but at a step before polymerization, suggesting that AlgK plays an important role in the polymerization of mannuronate to alginate.
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Affiliation(s)
- S Jain
- Department of Microbiology and Immunology, University of Tennessee and Veterans Affairs Medical Center, Memphis 38163, USA
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de Kievit TR, Lam JS. Isolation and characterization of two genes, waaC (rfaC) and waaF (rfaF), involved in Pseudomonas aeruginosa serotype O5 inner-core biosynthesis. J Bacteriol 1997; 179:3451-7. [PMID: 9171387 PMCID: PMC179135 DOI: 10.1128/jb.179.11.3451-3457.1997] [Citation(s) in RCA: 36] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023] Open
Abstract
Recent studies have provided evidence to implicate involvement of the core oligosaccharide region of Pseudomonas aeruginosa lipopolysaccharide (LPS) in adherence to host tissues. To better understand the role played by LPS in the virulence of this organism, the aim of the present study was to clone and characterize genes involved in core biosynthesis. The inner-core regions of P. aeruginosa and Salmonella enterica serovar Typhimurium are structurally very similar; both contain two main chain residues of heptose linked to lipid A-Kdo2 (Kdo is 3-deoxy-D-manno-octulosonic acid). By electrotransforming a P. aeruginosa PAO1 library into Salmonella waaC and waaF (formerly known as rfaC and rfaF, respectively) mutants, we were able to isolate the homologous heptosyltransferase I and II genes of P. aeruginosa. Two plasmids, pCOREc1 and pCOREc2, which restored smooth LPS production in the waaC mutant, were isolated. Similarly, plasmid pCOREf1 was able to complement the Salmonella waaF mutant. Sequence analysis of the DNA insert of pCOREc2 revealed one open reading frame (ORF) which could code for a protein of 39.8 kDa. The amino acid sequence of the deduced protein exhibited 53% identity with the sequence of the WaaC protein of S. enterica serovar Typhimurium. pCOREf1 contained one ORF capable of encoding a 38.4-kDa protein. The sequence of the predicted protein was 49% identical to the sequence of the Salmonella WaaF protein. Protein expression by the Maxicell system confirmed that a 40-kDa protein was encoded by pCOREc2 and a 38-kDa protein was encoded by pCOREf1. Pulsed-field gel electrophoresis was used to determine the map locations of the cloned waaC and waaF genes, which were found to lie between 0.9 and 6.6 min on the PAO1 chromosome. Using a gene-replacement strategy, we attempted to generate P. aeruginosa waaC and waaF null mutants. Despite multiple attempts to isolate true knockout mutants, all transconjugants were identified as merodiploids.
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Affiliation(s)
- T R de Kievit
- Department of Microbiology, University of Guelph, Ontario, Canada
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Abstract
Pseudomonas aeruginosa lipopolysaccharide (LPS) plays a key role in pathogenesis. In acute infections, a smooth LPS protects the organism from complement-mediated killing and, during chronic lung infections, an altered rough LPS helps the organism evade host defense mechanisms.
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Affiliation(s)
- J B Goldberg
- Dept of Microbiology, University of Virginia Health Sciences Center, Charlottesville 22908, USA.
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Govan JR, Deretic V. Microbial pathogenesis in cystic fibrosis: mucoid Pseudomonas aeruginosa and Burkholderia cepacia. Microbiol Rev 1996; 60:539-74. [PMID: 8840786 PMCID: PMC239456 DOI: 10.1128/mr.60.3.539-574.1996] [Citation(s) in RCA: 838] [Impact Index Per Article: 29.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Abstract
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 adaptation of this opportunistic pathogen to the chronic chourse of infection in CF, and on the innate resistance to antibiotics of B. cepacia, person-to-person spread, and sometimes rapidly fatal disease caused by this organism. While understanding the mechanism of conversion to mucoidy in P. aeruginosa has progressed to the point where this phenomenon has evolved into a model system for studying bacterial stress response in microbial pathogenesis, the more recent challenge with B. cepacia, which has emerged as a potent bona fide CF pathogen, is discussed in the context of clinical issues, taxonomy, transmission, and potential modes of pathogenicity.
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Affiliation(s)
- J R Govan
- Department of Medical Microbiology, University of Edinburgh Medical School, Scotland
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Coyne MJ, Goldberg JB. Cloning and characterization of the gene (rfc) encoding O-antigen polymerase of Pseudomonas aeruginosa PAO1. Gene 1995; 167:81-6. [PMID: 8566816 DOI: 10.1016/0378-1119(95)00595-1] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
The lipopolysaccharide (LPS) O-antigen polymerase is the product of the rfc gene. Loss of O-antigen polymerase activity due to mutation in rfc gives rise to a characteristic LPS phenotype known as core-plus-one or semi-rough, wherein the LPS core is capped with a single oligosaccharide unit. Pseudomonas aeruginosa (Pa) AK1401, a derivative of strain PAO1 (serogroup O5), expresses a semi-rough LPS; this mutant phenotype was complemented by a 2.2-kb NsiI-SacI fragment of Pa PAO1 DNA. Sequence analysis of this fragment revealed a 1317-bp open reading frame (ORF) potentially encoding a 438-amino-acid (aa) protein of 48,849 Da. This DNA sequence and the inferred aa sequence contain many of the features of other O-antigen polymerases, including an aberrantly low G + C content (particularly apparent in the high-G + C background of Pa), an unusual codon usage pattern, and a hydrophobicity profile indicative of a membrane protein. A 345-bp fragment internal to the ORF hybridized to genomic DNA from two of ten Pa serogroup strains examined by Southern blot; these two strains express O antigens structurally related to that of strain PAO1.
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Affiliation(s)
- M J Coyne
- Channing Laboratory, Department of Medicine, Brigham and Women's Hospital, Harvard Medical School, Boston, MA 02115-5899, USA
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Stroeher UH, Karageorgos LE, Brown MH, Morona R, Manning PA. A putative pathway for perosamine biosynthesis is the first function encoded within the rfb region of Vibrio cholerae O1. Gene X 1995; 166:33-42. [PMID: 8529891 DOI: 10.1016/0378-1119(95)00589-0] [Citation(s) in RCA: 41] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023] Open
Abstract
The first four genes (rfbA,B,D,E) of the rfb region of Vibrio cholerae O1 are predicted to encode the enzymes required for the biosynthesis of perosamine, which constitutes the backbone structure of the O-antigen of the lipopolysaccharide. Based on homology to known proteins/protein families, the following functions are predicted: RfbA, phosphomannose isomerase-guanosine diphosphomannose pyrophosphorylase; RfbB, phosphomanno-mutase; RfbD, oxido reductase and RfbE, perosamine synthetase (amino-transferase). Thus, perosamine is synthesized from fructose 6-phosphate via the intermediates mannose 6-phosphate by RfbA, to mannose 1-phosphate by RfbB, to GDP-mannose by RfbA, to GDP-4-keto-6-dideoxymannose by RfbD and to GDP-perosamine by RfbE. This final product would then serve as the substrate for the addition of the tetronate, which could then be polymerized into the O-antigen for transfer to the lipid A plus core oligosaccharide and export to the cell surface. The organization of these genes are such that one would expect them to be translationally coupled as part of the rfb operon. However, the absence of readily detectable promoter sequences suggests low levels of transcription, in line with other studies. The nucleotide sequence of these genes is absolutely conserved in the two isolates 569B (classical, Inaba) and O17 (El Tor, Ogawa) which were expected to show maximal sequence variation. This suggests very tight constraints on the micro-evolution within these sequences.
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Affiliation(s)
- U H Stroeher
- Department of Microbiology and Immunology, University of Adelaide, Australia
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Boyd A, Chakrabarty AM. Pseudomonas aeruginosa biofilms: role of the alginate exopolysaccharide. JOURNAL OF INDUSTRIAL MICROBIOLOGY 1995; 15:162-8. [PMID: 8519473 DOI: 10.1007/bf01569821] [Citation(s) in RCA: 168] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
Pseudomonas aeruginosa synthesizes an exopolysaccharide called alginate in response to environmental conditions. Alginate serves to protect the bacteria from adversity in its surroundings and also enhances adhesion to solid surfaces. Transcription of the alginate biosynthetic genes is induced upon attachment to the substratum and this leads to increased alginate production. As a result, biofilms develop which are advantageous to the survival and growth of the bacteria. In certain circumstances, P. aeruginosa produces an alginate lyase enzyme which cleaves the polymer into short oligosaccharides. This negates the anchoring properties of the alginate and results in increased detachment of the bacteria away from the surface, allowing them to spread and colonize new sites. Thus, both alginate biosynthetic and degradative enzymes are important for the development, maintenance and spread of P. aeruginosa biofilms.
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Affiliation(s)
- A Boyd
- Department of Microbiology and Immunology, University of Illinois, Chicago College of Medicine 60612, USA
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Deretic V, Schurr MJ, Yu H. Pseudomonas aeruginosa, mucoidy and the chronic infection phenotype in cystic fibrosis. Trends Microbiol 1995; 3:351-6. [PMID: 8520888 DOI: 10.1016/s0966-842x(00)88974-x] [Citation(s) in RCA: 97] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
During chronic infections in cystic fibrosis, persistence of Pseudomonas aeruginosa is associated with conversion into forms that are associated with conversion into forms that are characterized by a mucoid colony morphology, rough lipopolysaccharide and, paradoxically, decreased systemic virulence. The mutations underlying these changes occur in global regulators, such as alternative sigma factors and their accessory elements.
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Affiliation(s)
- V Deretic
- Dept of Microbiology, University of Texas Health Science Center at San Antonio 78284-7758, USA
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