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Kaplan JB, Cywes-Bentley C, Pier GB, Yakandawala N, Sailer M, Edwards MS, Kridin K. Poly- β-(1→6)- N-acetyl-D-glucosamine mediates surface attachment, biofilm formation, and biocide resistance in Cutibacterium acnes. Front Microbiol 2024; 15:1386017. [PMID: 38751716 PMCID: PMC11094747 DOI: 10.3389/fmicb.2024.1386017] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/14/2024] [Accepted: 04/17/2024] [Indexed: 05/18/2024] Open
Abstract
Background The commensal skin bacterium Cutibacterium acnes plays a role in the pathogenesis of acne vulgaris and also causes opportunistic infections of implanted medical devices due to its ability to form biofilms on biomaterial surfaces. Poly-β-(1→6)-N-acetyl-D-glucosamine (PNAG) is an extracellular polysaccharide that mediates biofilm formation and biocide resistance in a wide range of bacterial pathogens. The objective of this study was to determine whether C. acnes produces PNAG, and whether PNAG contributes to C. acnes biofilm formation and biocide resistance in vitro. Methods PNAG was detected on the surface of C. acnes cells by fluorescence confocal microscopy using the antigen-specific human IgG1 monoclonal antibody F598. PNAG was detected in C. acnes biofilms by measuring the ability of the PNAG-specific glycosidase dispersin B to inhibit biofilm formation and sensitize biofilms to biocide killing. Results Monoclonal antibody F598 bound to the surface of C. acnes cells. Dispersin B inhibited attachment of C. acnes cells to polystyrene rods, inhibited biofilm formation by C. acnes in glass and polypropylene tubes, and sensitized C. acnes biofilms to killing by benzoyl peroxide and tetracycline. Conclusion C. acnes produces PNAG, and PNAG contributes to C. acnes biofilm formation and biocide resistance in vitro. PNAG may play a role in C. acnes skin colonization, biocide resistance, and virulence in vivo.
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Affiliation(s)
- Jeffrey B. Kaplan
- Department of Biology, American University, Washington, DC, United States
- Laboratory for Skin Research, Institute for Medical Research, Galilee Medical Center, Nahariya, Israel
| | - Colette Cywes-Bentley
- Division of Infectious Diseases, Department of Medicine, Brigham and Women’s Hospital, Harvard Medical School, Boston, MA, United States
| | - Gerald B. Pier
- Division of Infectious Diseases, Department of Medicine, Brigham and Women’s Hospital, Harvard Medical School, Boston, MA, United States
| | | | | | | | - Khalaf Kridin
- Laboratory for Skin Research, Institute for Medical Research, Galilee Medical Center, Nahariya, Israel
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2
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Jakubovics NS, Goodman SD, Mashburn-Warren L, Stafford GP, Cieplik F. The dental plaque biofilm matrix. Periodontol 2000 2021; 86:32-56. [PMID: 33690911 PMCID: PMC9413593 DOI: 10.1111/prd.12361] [Citation(s) in RCA: 149] [Impact Index Per Article: 49.7] [Reference Citation Analysis] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Affiliation(s)
| | - Steven D Goodman
- Center for Microbial Pathogenesis, The Abigail Wexner Research Institute at Nationwide Children's Hospital, The Ohio State University College of Medicine, Columbus, Ohio, USA
| | - Lauren Mashburn-Warren
- Center for Microbial Pathogenesis, The Abigail Wexner Research Institute at Nationwide Children's Hospital, The Ohio State University College of Medicine, Columbus, Ohio, USA
| | - Graham P Stafford
- Integrated Biosciences, School of Clinical Dentistry, University of Sheffield, Sheffield, UK
| | - Fabian Cieplik
- Department of Conservative Dentistry and Periodontology, University Hospital Regensburg, Regensburg, Germany
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3
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Magana M, Sereti C, Ioannidis A, Mitchell CA, Ball AR, Magiorkinis E, Chatzipanagiotou S, Hamblin MR, Hadjifrangiskou M, Tegos GP. Options and Limitations in Clinical Investigation of Bacterial Biofilms. Clin Microbiol Rev 2018; 31:e00084-16. [PMID: 29618576 PMCID: PMC6056845 DOI: 10.1128/cmr.00084-16] [Citation(s) in RCA: 116] [Impact Index Per Article: 19.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
Abstract
Bacteria can form single- and multispecies biofilms exhibiting diverse features based upon the microbial composition of their community and microenvironment. The study of bacterial biofilm development has received great interest in the past 20 years and is motivated by the elegant complexity characteristic of these multicellular communities and their role in infectious diseases. Biofilms can thrive on virtually any surface and can be beneficial or detrimental based upon the community's interplay and the surface. Advances in the understanding of structural and functional variations and the roles that biofilms play in disease and host-pathogen interactions have been addressed through comprehensive literature searches. In this review article, a synopsis of the methodological landscape of biofilm analysis is provided, including an evaluation of the current trends in methodological research. We deem this worthwhile because a keyword-oriented bibliographical search reveals that less than 5% of the biofilm literature is devoted to methodology. In this report, we (i) summarize current methodologies for biofilm characterization, monitoring, and quantification; (ii) discuss advances in the discovery of effective imaging and sensing tools and modalities; (iii) provide an overview of tailored animal models that assess features of biofilm infections; and (iv) make recommendations defining the most appropriate methodological tools for clinical settings.
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Affiliation(s)
- Maria Magana
- Department of Clinical Microbiology, Athens Medical School, Aeginition Hospital, Athens, Greece
| | - Christina Sereti
- Department of Clinical Microbiology, Athens Medical School, Aeginition Hospital, Athens, Greece
- Department of Microbiology, Thriassio General Hospital, Attiki, Greece
| | - Anastasios Ioannidis
- Department of Clinical Microbiology, Athens Medical School, Aeginition Hospital, Athens, Greece
- Department of Nursing, Faculty of Human Movement and Quality of Life Sciences, University of Peloponnese, Sparta, Greece
| | - Courtney A Mitchell
- Department of Chemical and Biomolecular Engineering, Vanderbilt University, Nashville, Tennessee, USA
| | - Anthony R Ball
- Gliese 623b, Mendon, Massachusetts, USA
- GAMA Therapeutics LLC, Pepperell, Massachusetts, USA
| | - Emmanouil Magiorkinis
- Department of Hygiene, Epidemiology and Medical Statistics, Medical School, University of Athens, Athens-Goudi, Greece
| | | | - Michael R Hamblin
- Harvard-MIT Division of Health Science and Technology, Cambridge, Massachusetts, USA
- Department of Dermatology, Harvard Medical School, Boston, Massachusetts, USA
- Wellman Center for Photomedicine, Massachusetts General Hospital, Boston, Massachusetts, USA
| | - Maria Hadjifrangiskou
- Department of Pathology, Microbiology and Immunology, Vanderbilt University Medical Center, Nashville, Tennessee, USA
| | - George P Tegos
- Gliese 623b, Mendon, Massachusetts, USA
- GAMA Therapeutics LLC, Pepperell, Massachusetts, USA
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4
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Ebersole JL, Dawson D, Emecen-Huja P, Nagarajan R, Howard K, Grady ME, Thompson K, Peyyala R, Al-Attar A, Lethbridge K, Kirakodu S, Gonzalez OA. The periodontal war: microbes and immunity. Periodontol 2000 2017; 75:52-115. [DOI: 10.1111/prd.12222] [Citation(s) in RCA: 95] [Impact Index Per Article: 13.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
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5
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Shanmugam M, Oyeniyi AO, Parthiban C, Gujjarlapudi SK, Pier GB, Ramasubbu N. Role of de-N-acetylase PgaB from Aggregatibacter actinomycetemcomitans in exopolysaccharide export in biofilm mode of growth. Mol Oral Microbiol 2017; 32:500-510. [PMID: 28548373 DOI: 10.1111/omi.12188] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 05/22/2017] [Indexed: 11/29/2022]
Abstract
Aggregatibacter actinomycetemcomitans, a Gram-negative bacterium, is the causative agent of localized aggressive periodontitis. Attachment to a biotic surface is a critical first step in the A. actinomycetemcomitans infection process for which exopolysaccharides have been shown to be essential. In addition, the pga operon, containing genes encoding for biosynthetic proteins for poly-N-acetyl glucosamine (PNAG), plays a key role in A. actinomycetemcomitans virulence, as a mutant strain lacking the pga operon induces significantly less bone resorption. Among the genes in the pga operon, pgaB codes for a de-N-acetylase that is responsible for the deacetylation of the PNAG exopolysaccharide. Here we report the role of PgaB in regulation of virulence genes using a markerless, scarless deletion mutant targeting the coding region of the N-terminal catalytic domain of PgaB. The results demonstrate that the N-terminal, catalytic domain of PgaB is crucial for exopolysaccharide export.
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Affiliation(s)
- M Shanmugam
- Department of Oral Biology, Rutgers School of Dental Medicine, Newark, NJ, USA
| | - A O Oyeniyi
- Department of Oral Biology, Rutgers School of Dental Medicine, Newark, NJ, USA
| | - C Parthiban
- Department of Oral Biology, Rutgers School of Dental Medicine, Newark, NJ, USA
| | - S K Gujjarlapudi
- Department of Oral Biology, Rutgers School of Dental Medicine, Newark, NJ, USA
| | - G B Pier
- Department of Medicine, Brigham and Women's Hospital, Harvard Medical School, Boston, MA, USA
| | - N Ramasubbu
- Department of Oral Biology, Rutgers School of Dental Medicine, Newark, NJ, USA
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6
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Velusamy SK, Sampathkumar V, Godboley D, Fine DH. Survival of an Aggregatibacter actinomycetemcomitans quorum sensing luxS mutant in the mouths of Rhesus monkeys: insights into ecological adaptation. Mol Oral Microbiol 2017; 32:432-442. [PMID: 28383798 DOI: 10.1111/omi.12184] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/01/2022]
Abstract
Experiments were designed to explore a prominent autoinducer-2 (AI-2) producing gene (luxS) related to colonization and survival of Aggregatibacter actinomycetemcomitans, a low abundance member of the indigenous flora, that forms a key component of the dysbiotic flora in localized aggressive periodontitis. The luxS gene was disrupted in a primate strain of A. actinomycetemcomitans before implantation into the oral cavity of Rhesus monkeys (Rh). The colonization efficiency of the luxS mutant (RhAa-VS4) was compared with the parental wild-type strain (RhAa3) (positive control) and a ltxA mutant (RhAa-VS2) (negative control). The in vivo results showed that the luxS mutation had minimal impact on A. actinomycetemcomitans colonization compared with the wild-type RhAa3 strain. In vitro studies revealed that there was a significant upregulation of attachment-related genes aae, apiA, and flp in the RhAa-VS4 strain compared with RhAa3. Biofilm forming ability was also significantly increased in the RhAa-VS4 strain compared with RhAa3, whereas the AI-2 signal was ablated. The exogenous addition of the AI-2 precursor dihydroxy pentanedione allowed the RhAa-VS4 strain to achieve RhAa3 biofilm levels. This is the first primate study to test the relevance of LuxS in vivo. In vitro assessment suggests that in vivo survival of the RhAa-VS4 strain was due to the production of signaling AI-2 molecules derived from other members of the flora as well as the upregulation of genes related to attachment and biofilm formation.
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Affiliation(s)
- Senthil K Velusamy
- Department of Oral Biology, Rutgers School of Dental Medicine, Rutgers University, Newark, NJ, USA
| | - Vandana Sampathkumar
- Department of Oral Biology, Rutgers School of Dental Medicine, Rutgers University, Newark, NJ, USA
| | - Dipti Godboley
- Department of Oral Biology, Rutgers School of Dental Medicine, Rutgers University, Newark, NJ, USA
| | - Daniel H Fine
- Department of Oral Biology, Rutgers School of Dental Medicine, Rutgers University, Newark, NJ, USA
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7
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Parthiban C, Varudharasu D, Shanmugam M, Gopal P, Ragunath C, Thomas L, Nitz M, Ramasubbu N. Structural and functional analysis of de-N-acetylase PgaB from periodontopathogenAggregatibacter actinomycetemcomitans. Mol Oral Microbiol 2016; 32:324-340. [DOI: 10.1111/omi.12175] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 09/29/2016] [Indexed: 01/09/2023]
Affiliation(s)
- C. Parthiban
- Department of Oral Biology; Rutgers School of Dental Medicine; Newark NJ USA
| | - D. Varudharasu
- Selvam Structure Based Drug Design Laboratory; Selvam College of Technology; Namakkal Tamilnadu India
| | - M. Shanmugam
- Department of Oral Biology; Rutgers School of Dental Medicine; Newark NJ USA
| | - P. Gopal
- Department of Oral Biology; Rutgers School of Dental Medicine; Newark NJ USA
| | - C. Ragunath
- Scientific Chemical Technologies; Malden MA USA
| | - L. Thomas
- Department of Chemistry and Biochemistry; University of Oklahoma; Norman OK USA
| | - M. Nitz
- Department of Chemistry; University of Toronto; Toronto ON Canada
| | - N. Ramasubbu
- Department of Oral Biology; Rutgers School of Dental Medicine; Newark NJ USA
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8
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Complete Genome Sequence of Aggregatibacter actinomycetemcomitans Strain IDH781. GENOME ANNOUNCEMENTS 2016; 4:4/6/e01285-16. [PMID: 27834722 PMCID: PMC5105115 DOI: 10.1128/genomea.01285-16] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
We report here the complete genomic sequence and methylome of Aggregatibacter actinomycetemcomitans strain IDH781. This rough strain is used extensively as a model organism to characterize localized aggressive periodontitis pathogenesis, the basic biology and oral cavity colonization of A. actinomycetemcomitans, and its interactions with other members of the oral microbiome.
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9
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Domenech M, Pedrero-Vega E, Prieto A, García E. Evidence of the presence of nucleic acids and β-glucan in the matrix of non-typeable Haemophilus influenzae in vitro biofilms. Sci Rep 2016; 6:36424. [PMID: 27805043 PMCID: PMC5090351 DOI: 10.1038/srep36424] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/27/2016] [Accepted: 10/14/2016] [Indexed: 12/21/2022] Open
Abstract
Non-typeable Haemophilus influenzae (NTHi) is a Gram-negative bacterium that frequently colonizes the human nasopharynx; it is a common cause of chronic and recurrent otitis media in children and of exacerbations of chronic obstructive pulmonary disease. To date, no exopolysaccharide clearly contributing to NTHi biofilms has been identified. Consequently, there is some debate as to whether NTHi forms biofilms during colonization and infection. The present work shows that NTHi can form biofilms in vitro, producing an extracellular matrix composed of proteins, nucleic acids, and a β-glucan. Extracellular DNA, visualized by immunostaining and using fluorochromes, is an important component of this matrix and appears to be essential in biofilm maintenance. Extracellular RNA appears to be required only in the first steps of biofilm formation. Evidence of a matrix polysaccharide was obtained by staining with Calcofluor white M2R and by disaggregating biofilms with cellulase. Using strain 54997, residues of Glcp(1→4) in the NTHi biofilm were confirmed by gas-liquid chromatography-mass spectrometry. Evidence that N-acetyl-L-cysteine shows notable killing activity towards in vitro NTHi biofilm-forming bacteria is also provided.
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Affiliation(s)
- Mirian Domenech
- Departamento de Microbiología Molecular y Biología de las Infecciones, Centro de Investigaciones Biológicas (CSIC), Ramiro de Maeztu 9, 28040 Madrid, Spain
- CIBER de Enfermedades Respiratorias (CIBERES), Instituto de Salud Carlos III, Monforte de Lemos 3–5, 28029 Madrid, Spain
| | - Elena Pedrero-Vega
- Departamento de Microbiología Molecular y Biología de las Infecciones, Centro de Investigaciones Biológicas (CSIC), Ramiro de Maeztu 9, 28040 Madrid, Spain
| | - Alicia Prieto
- Departamento de Biología Medioambiental, Centro de Investigaciones Biológicas (CSIC), Ramiro de Maeztu 9, 28040 Madrid, Spain
| | - Ernesto García
- Departamento de Microbiología Molecular y Biología de las Infecciones, Centro de Investigaciones Biológicas (CSIC), Ramiro de Maeztu 9, 28040 Madrid, Spain
- CIBER de Enfermedades Respiratorias (CIBERES), Instituto de Salud Carlos III, Monforte de Lemos 3–5, 28029 Madrid, Spain
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10
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Velusamy SK, Sampathkumar V, Godboley D, Fine DH. Profound Effects of Aggregatibacter actinomycetemcomitans Leukotoxin Mutation on Adherence Properties Are Clarified in in vitro Experiments. PLoS One 2016; 11:e0151361. [PMID: 26977924 PMCID: PMC4792451 DOI: 10.1371/journal.pone.0151361] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/23/2015] [Accepted: 02/27/2016] [Indexed: 02/02/2023] Open
Abstract
Leukotoxin (Ltx) is a prominent virulence factor produced by Aggregatibacter actinomycetemcomitans, an oral microorganism highly associated with aggressive periodontitis. Ltx compromises host responsiveness by altering the viability of neutrophils, lymphocytes, and macrophages. Previously, we developed a Rhesus (Rh) monkey colonization model designed to determine the effect of virulence gene mutations on colonization of A. actinomycetemcomitans. Unexpectedly, an A. actinomycetemcomitans leukotoxin (ltxA) mutant (RhAa-VS2) failed to colonize in the Rh model. No previous literature suggested that Ltx was associated with A. actinomycetemcomitans binding to tooth surfaces. These results led us to explore the broad effects of the ltxA mutation in vitro. Results indicated that LtxA activity was completely abolished in RhAa-VS2 strain, while complementation significantly (P<0.0001) restored leukotoxicity compared to RhAa-VS2 strain. RT-PCR analysis of ltx gene expression ruled out polar effects. Furthermore, binding of RhAa-VS2 to salivary-coated hydroxyapatite (SHA) was significantly decreased (P<0.0001) compared to wild type RhAa3 strain. Real time RT-PCR analysis of the genes related to SHA binding in RhAa-VS2 showed that genes related to binding were downregulated [rcpA (P = 0.018), rcpB (P = 0.02), tadA (P = 0.002)] as compared to wild type RhAa3. RhAa-VS2 also exhibited decreased biofilm depth (P = 0.008) and exo-polysaccharide production (P<0.0001). Buccal epithelial cell (BEC) binding of RhAa-VS2 was unaffected. Complementation with ltxA restored binding to SHA (P<0.002) but had no effect on biofilm formation when compared to RhAa3. In conclusion, mutation of ltxA diminished hard tissue binding in vitro, which helps explain the previous in vivo failure of a ltxA knockout to colonize the Rh oral cavity. These results suggest that; 1) one specific gene knockout (in this case ltxA) could affect other seemingly unrelated genes (such as rcpA, rcpB tadA etc), and 2) some caution should be used when interpreting the effect attributed to targeted gene mutations when seen in a competitive in vivo environment.
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Affiliation(s)
- Senthil Kumar Velusamy
- Department of Oral Biology, Rutgers School of Dental Medicine, 185 South Orange Ave, Newark, New Jersey, United States of America
| | - Vandana Sampathkumar
- Department of Oral Biology, Rutgers School of Dental Medicine, 185 South Orange Ave, Newark, New Jersey, United States of America
| | - Dipti Godboley
- Department of Oral Biology, Rutgers School of Dental Medicine, 185 South Orange Ave, Newark, New Jersey, United States of America
| | - Daniel H. Fine
- Department of Oral Biology, Rutgers School of Dental Medicine, 185 South Orange Ave, Newark, New Jersey, United States of America
- * E-mail:
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11
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Herbert BA, Novince CM, Kirkwood KL. Aggregatibacter actinomycetemcomitans, a potent immunoregulator of the periodontal host defense system and alveolar bone homeostasis. Mol Oral Microbiol 2015. [PMID: 26197893 DOI: 10.1111/omi.12119] [Citation(s) in RCA: 84] [Impact Index Per Article: 9.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
Aggregatibacter actinomycetemcomitans is a perio-pathogenic bacteria that has long been associated with localized aggressive periodontitis. The mechanisms of its pathogenicity have been studied in humans and preclinical experimental models. Although different serotypes of A. actinomycetemcomitans have differential virulence factor expression, A. actinomycetemcomitans cytolethal distending toxin (CDT), leukotoxin, and lipopolysaccharide (LPS) have been most extensively studied in the context of modulating the host immune response. Following colonization and attachment in the oral cavity, A. actinomycetemcomitans employs CDT, leukotoxin, and LPS to evade host innate defense mechanisms and drive a pathophysiologic inflammatory response. This supra-physiologic immune response state perturbs normal periodontal tissue remodeling/turnover and ultimately has catabolic effects on periodontal tissue homeostasis. In this review, we have divided the host response into two systems: non-hematopoietic and hematopoietic. Non-hematopoietic barriers include epithelium and fibroblasts that initiate the innate immune host response. The hematopoietic system contains lymphoid and myeloid-derived cell lineages that are responsible for expanding the immune response and driving the pathophysiologic inflammatory state in the local periodontal microenvironment. Effector systems and signaling transduction pathways activated and utilized in response to A. actinomycetemcomitans will be discussed to further delineate immune cell mechanisms during A. actinomycetemcomitans infection. Finally, we will discuss the osteo-immunomodulatory effects induced by A. actinomycetemcomitans and dissect the catabolic disruption of balanced osteoclast-osteoblast-mediated bone remodeling, which subsequently leads to net alveolar bone loss.
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Affiliation(s)
- B A Herbert
- Department of Oral Health Sciences and the Center for Oral Health Research, Medical University of South Carolina, Charleston, SC, USA
| | - C M Novince
- Department of Oral Health Sciences and the Center for Oral Health Research, Medical University of South Carolina, Charleston, SC, USA
| | - K L Kirkwood
- Department of Oral Health Sciences and the Center for Oral Health Research, Medical University of South Carolina, Charleston, SC, USA.,Department of Microbiology and Immunology, Medical University of South Carolina, Charleston, SC, USA
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12
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Transcriptome Profiling of Wild-Type and pga-Knockout Mutant Strains Reveal the Role of Exopolysaccharide in Aggregatibacter actinomycetemcomitans. PLoS One 2015. [PMID: 26221956 PMCID: PMC4519337 DOI: 10.1371/journal.pone.0134285] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022] Open
Abstract
Exopolysaccharides have a diverse set of functions in most bacteria including a mechanistic role in protecting bacteria against environmental stresses. Among the many functions attributed to the exopolysaccharides, biofilm formation, antibiotic resistance, immune evasion and colonization have been studied most extensively. The exopolysaccharide produced by many Gram positive as well as Gram negative bacteria including the oral pathogen Aggregatibacter actinomycetemcomitans is the homopolymer of β(1,6)-linked N-acetylglucosamine. Recently, we reported that the PGA-deficient mutant of A. actinomycetemcomitans failed to colonize or induce bone resorption in a rat model of periodontal disease, and the colonization genes, apiA and aae, were significantly down regulated in the mutant strain. To understand the role of exopolysaccharide and the pga locus in the global expression of A. actinomycetemcomitans, we have used comparative transcriptome profiling to identify differentially expressed genes in the wild-type strain in relation to the PGA-deficient strain. Transcriptome analysis revealed that about 50% of the genes are differently expressed (P < 0.05 and fold change >1.5). Our study demonstrated that the absence of the pga locus affects the genes involved in peptidoglycan recycling, glycogen storage, and virulence. Further, using confocal microscopy and plating assays, we show that the viability of pga mutant strain is significantly reduced during biofilm growth. Thus, this study highlights the importance of pga genes and the exopolysaccharide in the virulence of A. actinomycetemcomitans.
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