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      1H NMR-Based Metabolite Profiling of Planktonic and Biofilm Cells in Acinetobacter baumannii 1656-2

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          Abstract

          Acinetobacter baumannii is an aerobic and gram-negative pathogenic bacterium that is resistant to most antibiotics. Recently, A. baumannii 1656-2 exhibited the ability to form biofilms under clinical conditions. In this study, global metabolite profiling of both planktonic and biofilm forms of A. baumannii 1656-2 was performed using high-resolution nuclear magnetic resonance (NMR) spectroscopy and multivariate statistical analysis to investigate the metabolic patterns leading to biofilm formation. Principal components analysis (PCA) and orthogonal partial least-squares discriminant analysis (OPLS-DA) score plots showed a distinct separation between planktonic and biofilm cells. Metabolites including acetates, pyruvate, succinate, UDP-glucose, AMP, glutamate, and lysine were increasingly involved in the energy metabolism of biofilm formation. In particular, the ratio of N-acetyl-D-glucosamine (GlcNAc) to D-glucosamine (GlcNH 2) was significantly higher during biofilm formation than under the planktonic condition. This study demonstrates that NMR-based global metabolite profiling of bacterial cells can provide valuable insight into the metabolic changes in multidrug resistant and biofilm-forming bacteria such as A. baumannii 1656-2.

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          Most cited references 26

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          A crucial role for exopolysaccharide modification in bacterial biofilm formation, immune evasion, and virulence.

          Biofilms play an important role in many chronic bacterial infections. Production of an extracellular mixture of sugar polymers called exopolysaccharide is characteristic and critical for biofilm formation. However, there is limited information about the mechanisms involved in the biosynthesis and modification of exopolysaccharide components and how these processes influence bacterial pathogenesis. Staphylococcus epidermidis is an important human pathogen that frequently causes persistent infections by biofilm formation on indwelling medical devices. It produces a poly-N-acetylglucosamine molecule that emerges as an exopolysaccharide component of many bacterial pathogens. Using a novel method based on size exclusion chromatography-mass spectrometry, we demonstrate that the surface-attached protein IcaB is responsible for deacetylation of the poly-N-acetylglucosamine molecule. Most likely due to the loss of its cationic character, non-deacetylated poly-acetylglucosamine in an isogenic icaB mutant strain was devoid of the ability to attach to the bacterial cell surface. Importantly, deacetylation of the polymer was essential for key virulence mechanisms of S. epidermidis, namely biofilm formation, colonization, and resistance to neutrophil phagocytosis and human antibacterial peptides. Furthermore, persistence of the icaB mutant strain was significantly impaired in a murine model of device-related infection. This is the first study to describe a mechanism of exopolysaccharide modification that is indispensable for the development of biofilm-associated human disease. Notably, this general virulence mechanism is likely similar for other pathogenic bacteria and constitutes an excellent target for therapeutic maneuvers aimed at combating biofilm-associated infection.
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            Capacity of multidrug-resistant clinical isolates of Acinetobacter baumannii to form biofilm and adhere to epithelial cell surfaces.

             H Y Seol,  D Cho,  T. J. Kim (2007)
            This study evaluated the capacity of 23 multidrug-resistant (MDR) clinical isolates of Acinetobacter baumannii to adhere to respiratory epithelial cell surfaces and to form biofilm on a polystyrene surface. All 23 A. baumannii isolates were capable of adhering efficiently to respiratory epithelial cells, and biofilm production was positively associated with epithelial cell adhesiveness (r 0.80, p <0.0001). In the presence of the chelating agent EDTA, biofilm formation was markedly reduced. Cell adhesiveness and biofilm formation were significantly higher in isolates carrying the bla(PER-1) gene as compared with isolates without this extended-spectrum beta-lactamase gene (p <0.005 and p <0.001, respectively). Further examination by RT-PCR showed a positive correlation between the level of expression of the bla(PER-1) gene and the level of biofilm formation (r 0.89, p <0.0001) and cell adhesiveness (r 0.74, p <0.006). Overall, the study demonstrated a high capacity of clinical isolates of MDR A. baumannii to form biofilm and to adhere to respiratory epithelial cells. This feature, combined with multidrug resistance, might contribute to the survival of these organisms and their dissemination in the hospital environment.
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              Depolymerization of beta-1,6-N-acetyl-D-glucosamine disrupts the integrity of diverse bacterial biofilms.

              Polymeric beta-1,6-N-acetyl-D-glucosamine (poly-beta-1,6-GlcNAc) has been implicated as an Escherichia coli and Staphylococcus epidermidis biofilm adhesin, the formation of which requires the pgaABCD and icaABCD loci, respectively. Enzymatic hydrolysis of poly-beta-1,6-GlcNAc, demonstrated for the first time by chromatography and mass spectrometry, disrupts biofilm formation by these species and by Yersinia pestis and Pseudomonas fluorescens, which possess pgaABCD homologues.
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                Author and article information

                Contributors
                Role: Editor
                Journal
                PLoS One
                PLoS ONE
                plos
                plosone
                PLoS ONE
                Public Library of Science (San Francisco, USA )
                1932-6203
                2013
                6 March 2013
                : 8
                : 3
                Affiliations
                [1 ]Integrated Metabolomics Research Group, Seoul Center, Korea Basic Science Institute, Seoul, Republic of Korea
                [2 ]Department of Microbiology, Kyungpook National University School of Medicine, Daegu, Republic of Korea
                [3 ]Department of Pharmacology, Dankook University College of Medicine, Cheonan, Republic of Korea
                [4 ]Graduate School of Analytical Science and Technology, Chungnam National University, Daejeon, Republic of Korea
                Imperial College London, United Kingdom
                Author notes

                Competing Interests: The authors have declared that no competing interests exist.

                Conceived and designed the experiments: JHS JK GSH. Performed the experiments: JY JHS JYY. Analyzed the data: JY JHS JYY JK GSH. Contributed reagents/materials/analysis tools: JY JHS JYY JK GSH. Wrote the paper: JY JHS JK GSH.

                Article
                PONE-D-12-30254
                10.1371/journal.pone.0057730
                3590295
                23483923

                This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.

                Page count
                Pages: 7
                Funding
                This study was supported by National Research Foundation Grants, no. 2010-0019394 (to G.S.H) and no.2010-0007203 (to J.K.) funded by the Ministry of Education, Science and Technology and the Korea Basic Science Institute (T32409). The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.
                Categories
                Research Article
                Biology
                Biochemistry
                Metabolism
                Metabolic Pathways
                Small Molecules
                Microbiology
                Bacterial Pathogens
                Gram Negative
                Medical Microbiology
                Microbial Growth and Development
                Microbial Metabolism
                Chemistry
                Analytical Chemistry
                Chemical Analysis
                Qualitative Analysis
                Quantitative Analysis
                Mathematics
                Statistics
                Biostatistics

                Uncategorized

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