1
|
Allen A, Habimana O, Casey E. The effects of extrinsic factors on the structural and mechanical properties of Pseudomonas fluorescens biofilms: A combined study of nutrient concentrations and shear conditions. Colloids Surf B Biointerfaces 2018; 165:127-134. [PMID: 29471219 DOI: 10.1016/j.colsurfb.2018.02.035] [Citation(s) in RCA: 22] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/29/2017] [Revised: 01/17/2018] [Accepted: 02/14/2018] [Indexed: 12/16/2022]
Abstract
The growth of biofilms on surfaces is a complicated process influenced by several environmental factors such as nutrient availability and fluid shear. In this study, combinations of growth conditions were selected for the study of Pseudomonas fluorescens biofilms including as cultivation time (24- or 48 h), nutrient levels (1:1 or 1:10 King B medium), and shear conditions (75 RPM shaking, 0.4 mL min -1 or 0.7 mL min -1). The use of Confocal Laser Scanning Microscopy (CLSM) determined biofilm structure, while liquid-phase Atomic Force Microscopy (AFM) techniques resolved the mechanical properties of biofilms. Under semi-static conditions, high nutrient environments led to more abundant biofilms with three times higher EPS content compared to biofilms grown under low nutrient conditions. AFM results revealed that biofilms formed under these conditions were less stiff, as shown by their Young's modulus values of 2.35 ± 0.08 kPa, compared to 4.98 ± 0.02 kPa for that of biofilms formed under low nutrient conditions. Under dynamic conditions, however, biofilms exposed to low nutrient conditions and high shear rates led to more developed biofilms compared to other tested dynamic conditions. These biofilms were also found to be significantly more adhesive compared to their counterparts grown at higher nutrient conditions.
Collapse
Affiliation(s)
- Ashley Allen
- School of Engineering, The University of Edinburgh, Edinburgh, UK
| | - Olivier Habimana
- School of Biological Sciences, The University of Hong Kong, Pokfulam, Hong Kong Special Administrative Region
| | - Eoin Casey
- School of Chemical and Bioprocess Engineering, University College Dublin (UCD), Belfield, Dublin 4, Ireland.
| |
Collapse
|
2
|
Broekema FI, van Oeveren W, Boerendonk A, Sharma PK, Bos RR. Hemostatic action of polyurethane foam with 55% polyethylene glycol compared to collagen and gelatin. Biomed Mater Eng 2016; 27:149-59. [DOI: 10.3233/bme-161578] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
Affiliation(s)
- Ferdinand I. Broekema
- Department of Oral and Maxillofacial Surgery, University Medical Center Groningen, University of Groningen, Groningen, The Netherlands
| | - Wim van Oeveren
- Department of Cardiothoracic Surgery, University Medical Center Groningen, University of Groningen, Groningen, The Netherlands
- Haemoscan, Stavangerweg 23-23, 9723 JC Groningen, The Netherlands
| | - Andrea Boerendonk
- Department of Oral and Maxillofacial Surgery, University Medical Center Groningen, University of Groningen, Groningen, The Netherlands
| | - Prashant K. Sharma
- Department of Biomedical Engineering (FB 40), W.J. Kolff Institute, University Medical Center Groningen, University of Groningen, P.O. Box 196, 9700 AD Groningen, The Netherlands
| | - Rudolf R.M. Bos
- Department of Oral and Maxillofacial Surgery, University Medical Center Groningen, University of Groningen, Groningen, The Netherlands
| |
Collapse
|
3
|
Peterson BW, He Y, Ren Y, Zerdoum A, Libera MR, Sharma PK, van Winkelhoff AJ, Neut D, Stoodley P, van der Mei HC, Busscher HJ. Viscoelasticity of biofilms and their recalcitrance to mechanical and chemical challenges. FEMS Microbiol Rev 2015; 39:234-45. [PMID: 25725015 PMCID: PMC4398279 DOI: 10.1093/femsre/fuu008] [Citation(s) in RCA: 177] [Impact Index Per Article: 19.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/12/2023] Open
Abstract
We summarize different studies describing mechanisms through which bacteria in a biofilm mode of growth resist mechanical and chemical challenges. Acknowledging previous microscopic work describing voids and channels in biofilms that govern a biofilms response to such challenges, we advocate a more quantitative approach that builds on the relation between structure and composition of materials with their viscoelastic properties. Biofilms possess features of both viscoelastic solids and liquids, like skin or blood, and stress relaxation of biofilms has been found to be a corollary of their structure and composition, including the EPS matrix and bacterial interactions. Review of the literature on viscoelastic properties of biofilms in ancient and modern environments as well as of infectious biofilms reveals that the viscoelastic properties of a biofilm relate with antimicrobial penetration in a biofilm. In addition, also the removal of biofilm from surfaces appears governed by the viscoelasticity of a biofilm. Herewith, it is established that the viscoelasticity of biofilms, as a corollary of structure and composition, performs a role in their protection against mechanical and chemical challenges. Pathways are discussed to make biofilms more susceptible to antimicrobials by intervening with their viscoelasticity, as a quantifiable expression of their structure and composition. Recalcitrance of biofilms against mechanical and chemical challenges has been looked at for ages from a microbiological perspective, but an approach based on viscoelastic properties of biofilms yields new insights in this recalcitrance.
Collapse
Affiliation(s)
- Brandon W Peterson
- University of Groningen and University Medical Center Groningen, Department of Biomedical Engineering, Antonius Deusinglaan 1, 9713 AV Groningen, The Netherlands
| | - Yan He
- University of Groningen and University Medical Center Groningen, Department of Biomedical Engineering, Antonius Deusinglaan 1, 9713 AV Groningen, The Netherlands University of Groningen and University Medical Center Groningen, Department of Orthodontics, Hanzeplein 1, 9700 RB Groningen, The Netherlands
| | - Yijin Ren
- University of Groningen and University Medical Center Groningen, Department of Orthodontics, Hanzeplein 1, 9700 RB Groningen, The Netherlands
| | - Aidan Zerdoum
- Department of Chemical Engineering and Materials Science, Stevens Institute of Technology, Hoboken, NJ 07030, Hoboken, New Jersey, USA
| | - Matthew R Libera
- Department of Chemical Engineering and Materials Science, Stevens Institute of Technology, Hoboken, NJ 07030, Hoboken, New Jersey, USA
| | - Prashant K Sharma
- University of Groningen and University Medical Center Groningen, Department of Biomedical Engineering, Antonius Deusinglaan 1, 9713 AV Groningen, The Netherlands
| | - Arie-Jan van Winkelhoff
- University of Groningen and University Medical Center Groningen, Center for Dentistry and Oral Hygiene, Anatonius Deusinglaan 1, 9713 AV Groningen, The Netherlands University of Groningen and University Medical Center Groningen, Department of Medical Microbiology, Hanzeplein 1, 9700 RB, Groningen, The Netherlands
| | - Danielle Neut
- University of Groningen and University Medical Center Groningen, Department of Biomedical Engineering, Antonius Deusinglaan 1, 9713 AV Groningen, The Netherlands
| | - Paul Stoodley
- Departments of Microbial Infection and Immunity and Orthopedics, Center for Microbial Interface Biology, The Ohio State University, 460 West 12th Avenue, Columbus, OH 43210, USA National Centre for Advanced Tribology at Southampton (nCATS), Engineering Sciences, University of Southampton, SO17 1BJ, UK
| | - Henny C van der Mei
- University of Groningen and University Medical Center Groningen, Department of Biomedical Engineering, Antonius Deusinglaan 1, 9713 AV Groningen, The Netherlands
| | - Henk J Busscher
- University of Groningen and University Medical Center Groningen, Department of Biomedical Engineering, Antonius Deusinglaan 1, 9713 AV Groningen, The Netherlands
| |
Collapse
|
4
|
Safari A, Tukovic Z, Walter M, Casey E, Ivankovic A. Mechanical properties of a mature biofilm from a wastewater system: from microscale to macroscale level. BIOFOULING 2015; 31:651-64. [PMID: 26371590 DOI: 10.1080/08927014.2015.1075981] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/28/2023]
Abstract
A fundamental understanding of biofilm mechanical stability is critical in order to describe detachment and develop biofouling control strategies. It is thus important to characterise the elastic deformation and flow behaviour of the biofilm under different modes of applied force. In this study, the mechanical properties of a mature wastewater biofilm were investigated with methods including macroscale compression and microscale indentation using atomic force microscopy (AFM). The mature biofilm was found to be mechanically isotropic at the macroscale level as its mechanical properties did not depend on the scales and modes of loading. However, the biofilm showed a tendency for mechanical inhomogeneity at the microscale level as indentation progressed deeper into the matrix. Moreover, it was observed that the adhesion force had a significant influence on the elastic properties of the biofilm at the surface, subjected to microscale tensile loading. These results are expected to inform a damage-based model for biofilm detachment.
Collapse
Affiliation(s)
- Ashkan Safari
- a School of Electrical, Electronic and Mechanical Engineering , University College Dublin (UCD) , Dublin , Ireland
| | - Zeljko Tukovic
- b Faculty of Mechanical Engineering and Naval Architecture , University of Zagreb , Zagreb , Croatia
| | - Maik Walter
- c School of Chemical and Bioprocess Engineering , University College Dublin (UCD) , Dublin , Ireland
| | - Eoin Casey
- c School of Chemical and Bioprocess Engineering , University College Dublin (UCD) , Dublin , Ireland
| | - Alojz Ivankovic
- a School of Electrical, Electronic and Mechanical Engineering , University College Dublin (UCD) , Dublin , Ireland
| |
Collapse
|
5
|
Peterson BW, Busscher HJ, Sharma PK, van der Mei HC. Visualization of microbiological processes underlying stress relaxation in Pseudomonas aeruginosa biofilms. MICROSCOPY AND MICROANALYSIS : THE OFFICIAL JOURNAL OF MICROSCOPY SOCIETY OF AMERICA, MICROBEAM ANALYSIS SOCIETY, MICROSCOPICAL SOCIETY OF CANADA 2014; 20:912-915. [PMID: 24621783 DOI: 10.1017/s1431927614000361] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/03/2023]
Abstract
Bacterial biofilms relieve themselves from external stresses through internal rearrangement, as mathematically modeled in many studies, but never microscopically visualized for their underlying microbiological processes. The aim of this study was to visualize rearrangement processes occurring in mechanically deformed biofilms using confocal-laser-scanning-microscopy after SYTO9 (green-fluorescent) and calcofluor-white (blue-fluorescent) staining to visualize bacteria and extracellular-polymeric matrix substances, respectively. We apply 20% uniaxial deformation to Pseudomonas aeruginosa biofilms and fix deformed biofilms prior to staining, after allowing different time-periods for relaxation. Two isogenic P. aeruginosa strains with different abilities to produce extracellular polymeric substances (EPS) were used. By confocal-laser-scanning-microscopy all biofilms showed intensity distributions for fluorescence from which rearrangement of EPS and bacteria in deformed biofilms were derived. For the P. aeruginosa strain producing EPS, bacteria could not find new, stable positions within 100 s after deformation, while EPS moved toward deeper layers within 20 s. Bacterial rearrangement was not seen in P. aeruginosa biofilms deficient in production of EPS. Thus, EPS is required to stimulate bacterial rearrangement in mechanically deformed biofilms within the time-scale of our experiments, and the mere presence of water is insufficient to induce bacterial movement, likely due to its looser association with the bacteria.
Collapse
Affiliation(s)
- Brandon W Peterson
- University of Groningen and University Medical Center Groningen,Department of Biomedical Engineering,Antonius Deusinglaan 1,9713 AV Groningen,The Netherlands
| | - Henk J Busscher
- University of Groningen and University Medical Center Groningen,Department of Biomedical Engineering,Antonius Deusinglaan 1,9713 AV Groningen,The Netherlands
| | - Prashant K Sharma
- University of Groningen and University Medical Center Groningen,Department of Biomedical Engineering,Antonius Deusinglaan 1,9713 AV Groningen,The Netherlands
| | - Henny C van der Mei
- University of Groningen and University Medical Center Groningen,Department of Biomedical Engineering,Antonius Deusinglaan 1,9713 AV Groningen,The Netherlands
| |
Collapse
|
6
|
Chen Y, van der Mei HC, Busscher HJ, Norde W. Viscous nature of the bond between adhering bacteria and substratum surfaces probed by atomic force microscopy. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2014; 30:3165-3169. [PMID: 24588204 DOI: 10.1021/la404874x] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/03/2023]
Abstract
Here we report on the viscous nature of the bond between adhering bacteria and a substratum surface. A tailor-made script was written for an atomic force microscope, that enabled a constant loading force of 1 or 5 nN to act for 30 s upon a bacterium compressed between a cantilever and a glass surface, while measuring its deformation. Time-dependent deformation was fitted to a one element Kelvin-Voigt analogue of the bond to yield a characteristic relaxation time and viscosity of the bond. Viscosities of streptococcal bonds were smaller (<20 kPa s) than those of staphylococcal bonds (>31 kPa s). Since staphylococci are relatively rich in extracellular polymeric substances, it can be inferred that the presence of extracellular polymeric substances yields the major contribution to the viscous response. The viscous nature of the bond between adhering bacteria and substratum surfaces provides the bacteria with more time to respond and protect themselves against external stresses.
Collapse
Affiliation(s)
- Yun Chen
- University of Groningen and University Medical Center Groningen , Department of Biomedical Engineering Antonius Deusinglaan 1, 9713 AV Groningen, The Netherlands
| | | | | | | |
Collapse
|
7
|
Abstract
Bacteria in the biofilm mode of growth are protected against chemical and mechanical stresses. Biofilms are composed, for the most part, of extracellular polymeric substances (EPSs). The extracellular matrix is composed of different chemical constituents, such as proteins, polysaccharides, and extracellular DNA (eDNA). Here we aimed to identify the roles of different matrix constituents in the viscoelastic response of biofilms. Staphylococcus aureus, Staphylococcus epidermidis, Streptococcus mutans, and Pseudomonas aeruginosa biofilms were grown under different conditions yielding distinct matrix chemistries. Next, biofilms were subjected to mechanical deformation and stress relaxation was monitored over time. A Maxwell model possessing an average of four elements for an individual biofilm was used to fit the data. Maxwell elements were defined by a relaxation time constant and their relative importance. Relaxation time constants varied widely over the 104 biofilms included and were divided into seven ranges (<1, 1 to 5, 5 to 10, 10 to 50, 50 to 100, 100 to 500, and >500 s). Principal-component analysis was carried out to eliminate related time constant ranges, yielding three principal components that could be related to the known matrix chemistries. The fastest relaxation component (<3 s) was due to the presence of water and soluble polysaccharides, combined with the absence of bacteria, i.e., the heaviest masses in a biofilm. An intermediate component (3 to 70 s) was related to other EPSs, while a distinguishable role was assigned to intact eDNA, which possesses a unique principal component with a time constant range (10 to 25 s) between those of EPS constituents. This implies that eDNA modulates its interaction with other matrix constituents to control its contribution to viscoelastic relaxation under mechanical stress. The protection offered by biofilms to organisms that inhabit it against chemical and mechanical stresses is due in part to its matrix of extracellular polymeric substances (EPSs) in which biofilm organisms embed themselves. Mechanical stresses lead to deformation and possible detachment of biofilm organisms, and hence, rearrangement processes occur in a biofilm to relieve it from these stresses. Maxwell analysis of stress relaxation allows the determination of characteristic relaxation time constants, but the biofilm components and matrix constituents associated with different stress relaxation processes have never been identified. Here we grew biofilms with different matrix constituents and used principal-component analysis to reveal that the presence of water and soluble polysaccharides, together with the absence of bacteria, is associated with the fastest relaxation, while other EPSs control a second, slower relaxation. Extracellular DNA, as a matrix constituent, had a distinguishable role with its own unique principal component in stress relaxation with a time constant range between those of other EPSs.
Collapse
|
8
|
He Y, Peterson BW, Jongsma MA, Ren Y, Sharma PK, Busscher HJ, van der Mei HC. Stress relaxation analysis facilitates a quantitative approach towards antimicrobial penetration into biofilms. PLoS One 2013; 8:e63750. [PMID: 23723995 PMCID: PMC3664570 DOI: 10.1371/journal.pone.0063750] [Citation(s) in RCA: 39] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/30/2013] [Accepted: 03/26/2013] [Indexed: 12/19/2022] Open
Abstract
Biofilm-related infections can develop everywhere in the human body and are rarely cleared by the host immune system. Moreover, biofilms are often tolerant to antimicrobials, due to a combination of inherent properties of bacteria in their adhering, biofilm mode of growth and poor physical penetration of antimicrobials through biofilms. Current understanding of biofilm recalcitrance toward antimicrobial penetration is based on qualitative descriptions of biofilms. Here we hypothesize that stress relaxation of biofilms will relate with antimicrobial penetration. Stress relaxation analysis of single-species oral biofilms grown in vitro identified a fast, intermediate and slow response to an induced deformation, corresponding with outflow of water and extracellular polymeric substances, and bacterial re-arrangement, respectively. Penetration of chlorhexidine into these biofilms increased with increasing relative importance of the slow and decreasing importance of the fast relaxation element. Involvement of slow relaxation elements suggests that biofilm structures allowing extensive bacterial re-arrangement after deformation are more open, allowing better antimicrobial penetration. Involvement of fast relaxation elements suggests that water dilutes the antimicrobial upon penetration to an ineffective concentration in deeper layers of the biofilm. Next, we collected biofilms formed in intra-oral collection devices bonded to the buccal surfaces of the maxillary first molars of human volunteers. Ex situ chlorhexidine penetration into two weeks old in vivo formed biofilms followed a similar dependence on the importance of the fast and slow relaxation elements as observed for in vitro formed biofilms. This study demonstrates that biofilm properties can be derived that quantitatively explain antimicrobial penetration into a biofilm.
Collapse
Affiliation(s)
- Yan He
- Department of Biomedical Engineering, W.J. Kolff Institute, University Medical Center Groningen and University of Groningen, Groningen, The Netherlands
| | - Brandon W. Peterson
- Department of Biomedical Engineering, W.J. Kolff Institute, University Medical Center Groningen and University of Groningen, Groningen, The Netherlands
| | - Marije A. Jongsma
- Department of Orthodontics, University Medical Center Groningen, University of Groningen, Groningen, The Netherlands
| | - Yijin Ren
- Department of Orthodontics, University Medical Center Groningen, University of Groningen, Groningen, The Netherlands
| | - Prashant K. Sharma
- Department of Biomedical Engineering, W.J. Kolff Institute, University Medical Center Groningen and University of Groningen, Groningen, The Netherlands
| | - Henk J. Busscher
- Department of Biomedical Engineering, W.J. Kolff Institute, University Medical Center Groningen and University of Groningen, Groningen, The Netherlands
| | - Henny C. van der Mei
- Department of Biomedical Engineering, W.J. Kolff Institute, University Medical Center Groningen and University of Groningen, Groningen, The Netherlands
- * E-mail:
| |
Collapse
|