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Bowden LC, Finlinson J, Jones B, Berges BK. Beyond the double helix: the multifaceted landscape of extracellular DNA in Staphylococcus aureus biofilms. Front Cell Infect Microbiol 2024; 14:1400648. [PMID: 38903938 PMCID: PMC11188362 DOI: 10.3389/fcimb.2024.1400648] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/18/2024] [Accepted: 05/17/2024] [Indexed: 06/22/2024] Open
Abstract
Staphylococcus aureus forms biofilms consisting of cells embedded in a matrix made of proteins, polysaccharides, lipids, and extracellular DNA (eDNA). Biofilm-associated infections are difficult to treat and can promote antibiotic resistance, resulting in negative healthcare outcomes. eDNA within the matrix contributes to the stability, growth, and immune-evasive properties of S. aureus biofilms. eDNA is released by autolysis, which is mediated by murein hydrolases that access the cell wall via membrane pores formed by holin-like proteins. The eDNA content of S. aureus biofilms varies among individual strains and is influenced by environmental conditions, including the presence of antibiotics. eDNA plays an important role in biofilm development and structure by acting as an electrostatic net that facilitates protein-cell and cell-cell interactions. Because of eDNA's structural importance in biofilms and its ubiquitous presence among S. aureus isolates, it is a potential target for therapeutics. Treatment of biofilms with DNase can eradicate or drastically reduce them in size. Additionally, antibodies that target DNABII proteins, which bind to and stabilize eDNA, can also disperse biofilms. This review discusses the recent literature on the release, structure, and function of eDNA in S. aureus biofilms, in addition to a discussion of potential avenues for targeting eDNA for biofilm eradication.
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Affiliation(s)
| | | | | | - Bradford K. Berges
- Department of Microbiology and Molecular Biology, Brigham Young University, Provo, UT, United States
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Mahadevaswamy UR, Mugunthan S, Seviour T, Kjelleberg S, Lim S. Evaluating a polymicrobial biofilm model for structural components by co-culturing Komagataeibacter hansenii produced bacterial cellulose with Pseudomonas aeruginosa PAO1. Biofilm 2024; 7:100176. [PMID: 38322579 PMCID: PMC10845243 DOI: 10.1016/j.bioflm.2024.100176] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/20/2023] [Revised: 12/21/2023] [Accepted: 01/04/2024] [Indexed: 02/08/2024] Open
Abstract
A polymicrobial biofilm model of Komagataeibacter hansenii and Pseudomonas aeruginosa was developed to understand whether a pre-existing matrix affects the ability of another species to build a biofilm. P. aeruginosa was inoculated onto the preformed K. hansenii biofilm consisting of a cellulose matrix. P. aeruginosa PAO1 colonized and infiltrated the K. hansenii bacterial cellulose biofilm (BC), as indicated by the presence of cells at 19 μm depth in the translucent hydrogel matrix. Bacterial cell density increased along the imaged depth of the biofilm (17-19 μm). On day 5, the average bacterial count across sections was 67 ± 4 % P. aeruginosa PAO1 and 33 ± 6 % K. hansenii. Biophysical characterization of the biofilm indicated that colonization by P. aeruginosa modified the biophysical properties of the BC matrix, which inlcuded increased density, heterogeneity, degradation temperature and thermal stability, and reduced crystallinity, swelling ability and moisture content. This further indicates colonization of the biofilm by P. aeruginosa. While eDNA fibres - a key viscoelastic component of P. aeruginosa biofilm - were present on the surface of the co-cultured biofilm on day 1, their abundance decreased over time, and by day 5, no eDNA was observed, either on the surface or within the matrix. P. aeruginosa-colonized biofilm devoid of eDNA retained its mechanical properties. The observations demonstrate that a pre-existing biofilm scaffold of K. hansenii inhibits P. aeruginosa PAO1 eDNA production and suggest that eDNA production is a response by P. aeruginosa to the viscoelastic properties of its environment.
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Affiliation(s)
- Usha Rani Mahadevaswamy
- School of Chemistry, Chemical Engineering and Biotechnology, Nanyang Technological University, Singapore
| | - Sudarsan Mugunthan
- Singapore Centre for Environmental Life Sciences Engineering, Nanyang Technological University, Singapore
| | - Thomas Seviour
- Singapore Centre for Environmental Life Sciences Engineering, Nanyang Technological University, Singapore
- Centre for Water Technology (WATEC), Department of Biological and Chemical Engineering, Aarhus University, Aarhus, 8000, Denmark
| | - Staffan Kjelleberg
- Singapore Centre for Environmental Life Sciences Engineering, Nanyang Technological University, Singapore
- School of Biological Sciences, Nanyang Technological University, Singapore
- School of Biological, Earth and Environmental Sciences, University of New South Wales, Sydney, Australia
| | - Sierin Lim
- School of Chemistry, Chemical Engineering and Biotechnology, Nanyang Technological University, Singapore
- Nanyang Environment and Water Research Institute, Nanyang Technological University, Singapore
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Minero GA, Møllebjerg A, Thiesen C, Johansen M, Jørgensen N, Birkedal V, Otzen DE, Meyer R. Extracellular G-quadruplexes and Z-DNA protect biofilms from DNase I, and G-quadruplexes form a DNAzyme with peroxidase activity. Nucleic Acids Res 2024; 52:1575-1590. [PMID: 38296834 PMCID: PMC10939358 DOI: 10.1093/nar/gkae034] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/30/2023] [Revised: 01/04/2024] [Accepted: 01/10/2024] [Indexed: 02/02/2024] Open
Abstract
Many bacteria form biofilms to protect themselves from predators or stressful environmental conditions. In the biofilm, bacteria are embedded in a protective extracellular matrix composed of polysaccharides, proteins and extracellular DNA (eDNA). eDNA most often is released from lysed bacteria or host mammalian cells, and it is the only matrix component most biofilms appear to have in common. However, little is known about the form DNA takes in the extracellular space, and how different non-canonical DNA structures such as Z-DNA or G-quadruplexes might contribute to its function in the biofilm. The aim of this study was to determine if non-canonical DNA structures form in eDNA-rich staphylococcal biofilms, and if these structures protect the biofilm from degradation by nucleases. We grew Staphylococcus epidermidis biofilms in laboratory media supplemented with hemin and NaCl to stabilize secondary DNA structures and visualized their location by immunolabelling and fluorescence microscopy. We furthermore visualized the macroscopic biofilm structure by optical coherence tomography. We developed assays to quantify degradation of Z-DNA and G-quadruplex DNA oligos by different nucleases, and subsequently investigated how these enzymes affected eDNA in the biofilms. Z-DNA and G-quadruplex DNA were abundant in the biofilm matrix, and were often present in a web-like structures. In vitro, the structures did not form in the absence of NaCl or mechanical shaking during biofilm growth, or in bacterial strains deficient in eDNA or exopolysaccharide production. We thus infer that eDNA and polysaccharides interact, leading to non-canonical DNA structures under mechanical stress when stabilized by salt. We also confirmed that G-quadruplex DNA and Z-DNA was present in biofilms from infected implants in a murine implant-associated osteomyelitis model. Mammalian DNase I lacked activity against Z-DNA and G-quadruplex DNA, while Micrococcal nuclease could degrade G-quadruplex DNA and S1 Aspergillus nuclease could degrade Z-DNA. Micrococcal nuclease, which originates from Staphylococcus aureus, may thus be key for dispersal of biofilm in staphylococci. In addition to its structural role, we show for the first time that the eDNA in biofilms forms a DNAzyme with peroxidase-like activity in the presence of hemin. While peroxidases are part of host defenses against pathogens, we now show that biofilms can possess intrinsic peroxidase activity in the extracellular matrix.
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Affiliation(s)
| | - Andreas Møllebjerg
- Interdisciplinary Nanoscience Center (iNANO), Aarhus University, Gustav Wieds Vej 14, 8000 Aarhus, Denmark
| | - Celine Thiesen
- Interdisciplinary Nanoscience Center (iNANO), Aarhus University, Gustav Wieds Vej 14, 8000 Aarhus, Denmark
| | - Mikkel Illemann Johansen
- Department Infectious Diseases, Aarhus University Hospital, Palle Juul-Jensens bvld 99, 8200 Aarhus N, Denmark
| | - Nis Pedersen Jørgensen
- Department Infectious Diseases, Aarhus University Hospital, Palle Juul-Jensens bvld 99, 8200 Aarhus N, Denmark
| | - Victoria Birkedal
- Interdisciplinary Nanoscience Center (iNANO), Aarhus University, Gustav Wieds Vej 14, 8000 Aarhus, Denmark
- Department of Chemistry, Aarhus University, Langelandsgade 140, 8000 Aarhus, Denmark
| | - Daniel Erik Otzen
- Interdisciplinary Nanoscience Center (iNANO), Aarhus University, Gustav Wieds Vej 14, 8000 Aarhus, Denmark
- Department of Molecular Biology and Genetics, Aarhus University, Universitetsbyen 81, 8000 Aarhus, Denmark
| | - Rikke Louise Meyer
- Interdisciplinary Nanoscience Center (iNANO), Aarhus University, Gustav Wieds Vej 14, 8000 Aarhus, Denmark
- Department of Biology, Aarhus University, Ny Munkegade 114, 8000 Aarhus, Denmark
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Ndukwe ARN, Qin J, Wiedbrauk S, Boase NRB, Fairfull-Smith KE, Totsika M. In Vitro Activities of Oxazolidinone Antibiotics Alone and in Combination with C-TEMPO against Methicillin-Resistant Staphylococcus aureus Biofilms. Antibiotics (Basel) 2023; 12:1706. [PMID: 38136740 PMCID: PMC10741017 DOI: 10.3390/antibiotics12121706] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/09/2023] [Revised: 12/04/2023] [Accepted: 12/04/2023] [Indexed: 12/24/2023] Open
Abstract
Infections caused by methicillin-resistant Staphylococcus aureus (MRSA) are a global health concern. The propensity of MRSA to form biofilms is a significant contributor to its pathogenicity. Strategies to treat biofilms often involve small molecules that disperse the biofilm into planktonic cells. Linezolid and, by extension, theoxazolidinones have been developed to treat infections caused by Gram-positive bacteria such as MRSA. However, the clinical development of these antibiotics has mainly assessed the susceptibility of planktonic cells to the drug. Previous studies evaluating the anti-biofilm activity of theoxazolidinones have mainly focused on the biofilm inhibition of Enterococcus faecalis and methicillin-sensitive Staphylococcus aureus, with only a few studies investigating the activity of oxazolidinones for eradicating established biofilms for these species. Very little is known about the ability of oxazolidinones to eradicate MRSA biofilms. In this work, five oxazolidinones were assessed against MRSA biofilms using a minimum biofilm eradication concentration (MBEC) assay. All oxazolidinones had inherent antibiofilm activity. However, only ranbezolid could completely eradicate MRSA biofilms at clinically relevant concentrations. The susceptibility of the MRSA biofilms to ranbezolid was synergistically enhanced by coadministration with the nitroxide biofilm dispersal agent C-TEMPO. We presume that ranbezolid acts as a dual warhead drug, which combines the mechanism of action of the oxazolidinones with a nitric oxide donor or cytotoxic drug.
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Affiliation(s)
- Audrey R. N. Ndukwe
- Centre for Immunology and Infection Control, School of Biomedical Sciences, Faculty of Health, Queensland University of Technology, Brisbane, QLD 4001, Australia; (A.R.N.N.); (J.Q.)
- School of Chemistry and Physics, Queensland University of Technology, Brisbane, QLD 4001, Australia; (S.W.); (N.R.B.B.); (K.E.F.-S.)
- Centre for Materials Science, Queensland University of Technology, Brisbane, QLD 4001, Australia
| | - Jilong Qin
- Centre for Immunology and Infection Control, School of Biomedical Sciences, Faculty of Health, Queensland University of Technology, Brisbane, QLD 4001, Australia; (A.R.N.N.); (J.Q.)
| | - Sandra Wiedbrauk
- School of Chemistry and Physics, Queensland University of Technology, Brisbane, QLD 4001, Australia; (S.W.); (N.R.B.B.); (K.E.F.-S.)
- Centre for Materials Science, Queensland University of Technology, Brisbane, QLD 4001, Australia
| | - Nathan R. B. Boase
- School of Chemistry and Physics, Queensland University of Technology, Brisbane, QLD 4001, Australia; (S.W.); (N.R.B.B.); (K.E.F.-S.)
- Centre for Materials Science, Queensland University of Technology, Brisbane, QLD 4001, Australia
| | - Kathryn E. Fairfull-Smith
- School of Chemistry and Physics, Queensland University of Technology, Brisbane, QLD 4001, Australia; (S.W.); (N.R.B.B.); (K.E.F.-S.)
- Centre for Materials Science, Queensland University of Technology, Brisbane, QLD 4001, Australia
| | - Makrina Totsika
- Centre for Immunology and Infection Control, School of Biomedical Sciences, Faculty of Health, Queensland University of Technology, Brisbane, QLD 4001, Australia; (A.R.N.N.); (J.Q.)
- Max Planck Queensland Centre, Queensland University of Technology, Brisbane, QLD 4001, Australia
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