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Relucenti M, Familiari G, Donfrancesco O, Taurino M, Li X, Chen R, Artini M, Papa R, Selan L. Microscopy Methods for Biofilm Imaging: Focus on SEM and VP-SEM Pros and Cons. BIOLOGY 2021; 10:biology10010051. [PMID: 33445707 PMCID: PMC7828176 DOI: 10.3390/biology10010051] [Citation(s) in RCA: 63] [Impact Index Per Article: 21.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 12/10/2020] [Revised: 12/30/2020] [Accepted: 01/07/2021] [Indexed: 12/11/2022]
Abstract
Simple Summary Bacterial biofilms cause infections that are often resistant to antibiotic treatments. Research about the formation and elimination of biofilms cannot be undertaken without detailed imaging techniques. In this review, traditional and cutting-edge microscopy methods to study biofilm structure, ultrastructure, and 3-D architecture, with particular emphasis on conventional scanning electron microscopy and variable pressure scanning electron microscopy, are addressed, with the respective advantages and disadvantages. When ultrastructural characterization of biofilm matrix and its embedded bacterial cells is needed, as in studies on the effects of drug treatments on biofilm, scanning electron microscopy with customized protocols such as the osmium tetroxide (OsO4), ruthenium red (RR), tannic acid (TA), and ionic liquid (IL) must be preferred over other methods for the following: unparalleled image quality, magnification and resolution, minimal sample loss, and actual sample structure preservation. The first step to make a morphological assessment of the effect of the various pharmacological treatments on clinical biofilms is the production of images that faithfully reflect the structure of the sample. The extraction of quantitative parameters from images, possible using specific software, will allow for the scanning electron microscopy morphological evaluation to no longer be considered as an accessory technique, but a quantitative method to all effects. Abstract Several imaging methodologies have been used in biofilm studies, contributing to deepening the knowledge on their structure. This review illustrates the most widely used microscopy techniques in biofilm investigations, focusing on traditional and innovative scanning electron microscopy techniques such as scanning electron microscopy (SEM), variable pressure SEM (VP-SEM), environmental SEM (ESEM), and the more recent ambiental SEM (ASEM), ending with the cutting edge Cryo-SEM and focused ion beam SEM (FIB SEM), highlighting the pros and cons of several methods with particular emphasis on conventional SEM and VP-SEM. As each technique has its own advantages and disadvantages, the choice of the most appropriate method must be done carefully, based on the specific aim of the study. The evaluation of the drug effects on biofilm requires imaging methods that show the most detailed ultrastructural features of the biofilm. In this kind of research, the use of scanning electron microscopy with customized protocols such as osmium tetroxide (OsO4), ruthenium red (RR), tannic acid (TA) staining, and ionic liquid (IL) treatment is unrivalled for its image quality, magnification, resolution, minimal sample loss, and actual sample structure preservation. The combined use of innovative SEM protocols and 3-D image analysis software will allow for quantitative data from SEM images to be extracted; in this way, data from images of samples that have undergone different antibiofilm treatments can be compared.
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Affiliation(s)
- Michela Relucenti
- Department of Anatomy, Histology, Forensic Medicine and Orthopedics, Sapienza University of Rome, Via Alfonso Borelli 50, 00161 Rome, Italy; (G.F.); (O.D.)
- Correspondence: ; Tel.: +39-0649918061
| | - Giuseppe Familiari
- Department of Anatomy, Histology, Forensic Medicine and Orthopedics, Sapienza University of Rome, Via Alfonso Borelli 50, 00161 Rome, Italy; (G.F.); (O.D.)
| | - Orlando Donfrancesco
- Department of Anatomy, Histology, Forensic Medicine and Orthopedics, Sapienza University of Rome, Via Alfonso Borelli 50, 00161 Rome, Italy; (G.F.); (O.D.)
| | - Maurizio Taurino
- Department of Clinical and Molecular Medicine, Unit of Vascular Surgery, Sant’Andrea Hospital, Sapienza University of Rome, Via di Grottarossa 1039, 00189 Rome, Italy;
| | - Xiaobo Li
- Key Laboratory of Environmental Medicine Engineering, Ministry of Education, School of Public Health, Southeast University, Nanjing 210096, China; (X.L.); (R.C.)
| | - Rui Chen
- Key Laboratory of Environmental Medicine Engineering, Ministry of Education, School of Public Health, Southeast University, Nanjing 210096, China; (X.L.); (R.C.)
| | - Marco Artini
- Department of Public Health and Infectious Diseases, Sapienza University of Rome, P.le Aldo Moro 5, 00185 Rome, Italy; (M.A.); (R.P.); (L.S.)
| | - Rosanna Papa
- Department of Public Health and Infectious Diseases, Sapienza University of Rome, P.le Aldo Moro 5, 00185 Rome, Italy; (M.A.); (R.P.); (L.S.)
| | - Laura Selan
- Department of Public Health and Infectious Diseases, Sapienza University of Rome, P.le Aldo Moro 5, 00185 Rome, Italy; (M.A.); (R.P.); (L.S.)
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Characterization of Scardovia wiggsiae Biofilm by Original Scanning Electron Microscopy Protocol. Microorganisms 2020; 8:microorganisms8060807. [PMID: 32471210 PMCID: PMC7355790 DOI: 10.3390/microorganisms8060807] [Citation(s) in RCA: 29] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/20/2020] [Revised: 05/22/2020] [Accepted: 05/26/2020] [Indexed: 01/11/2023] Open
Abstract
Early childhood caries (ECC) is a severe manifestation of carious pathology with rapid and disruptive progression. The ECC microbiota includes a wide variety of bacterial species, among which is an anaerobic newly named species, Scardovia wiggsiae, a previously unidentified Bifidobacterium. Our aim was to provide the first ultrastructural characterization of S. wiggsiae and its biofilm by scanning electron microscopy (SEM) using a protocol that faithfully preserved the biofilm architecture and allowed an investigation at very high magnifications (order of nanometers) and with the appropriate resolution. To accomplish this task, we analyzed Streptococcus mutans’ biofilm by conventional SEM and VP-SEM protocols, in addition, we developed an original procedure, named OsO4-RR-TA-IL, which avoids dehydration, drying and sputter coating. This innovative protocol allowed high-resolution and high-magnification imaging (from 10000× to 35000×) in high-vacuum and high-voltage conditions. After comparing three methods, we chose OsO4-RR-TA-IL to investigate S. wiggsiae. It appeared as a fusiform elongated bacterium, without surface specialization, arranged in clusters and submerged in a rich biofilm matrix, which showed a well-developed micro-canalicular system. Our results provide the basis for the development of innovative strategies to quantify the effects of different treatments, in order to establish the best option to counteract ECC in pediatric patients.
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Microridges are apical epithelial projections formed of F-actin networks that organize the glycan layer. Sci Rep 2019; 9:12191. [PMID: 31434932 PMCID: PMC6704121 DOI: 10.1038/s41598-019-48400-0] [Citation(s) in RCA: 25] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/12/2018] [Accepted: 07/29/2019] [Indexed: 11/16/2022] Open
Abstract
Apical projections are integral functional units of epithelial cells. Microvilli and stereocilia are cylindrical apical projections that are formed of bundled actin. Microridges on the other hand, extend laterally, forming labyrinthine patterns on surfaces of various kinds of squamous epithelial cells. So far, the structural organization and functions of microridges have remained elusive. We have analyzed microridges on zebrafish epidermal cells using confocal and electron microscopy methods including electron tomography, to show that microridges are formed of F-actin networks and require the function of the Arp2/3 complex for their maintenance. During development, microridges begin as F-actin punctae showing signatures of branching and requiring an active Arp2/3 complex. Using inhibitors of actin polymerization and the Arp2/3 complex, we show that microridges organize the surface glycan layer. Our analyses have unraveled the F-actin organization supporting the most abundant and evolutionarily conserved apical projection, which functions in glycan organization.
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García-Fraile P, Benada O, Cajthaml T, Baldrian P, Lladó S. Terracidiphilus gabretensis gen. nov., sp. nov., an Abundant and Active Forest Soil Acidobacterium Important in Organic Matter Transformation. Appl Environ Microbiol 2016; 82:560-9. [PMID: 26546425 PMCID: PMC4711116 DOI: 10.1128/aem.03353-15] [Citation(s) in RCA: 33] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/13/2015] [Accepted: 11/02/2015] [Indexed: 01/22/2023] Open
Abstract
Understanding the activity of bacteria in coniferous forests is highly important, due to the role of these environments as a global carbon sink. In a study of the microbial biodiversity of montane coniferous forest soil in the Bohemian Forest National Park (Czech Republic), we succeeded in isolating bacterial strain S55(T), which belongs to one of the most abundant operational taxonomic units (OTUs) in active bacterial populations, according to the analysis of RNA-derived 16S rRNA amplicons. The 16S rRNA gene sequence analysis showed that the species most closely related to strain S55(T) include Bryocella elongata SN10(T) (95.4% identity), Acidicapsa ligni WH120(T) (95.2% identity), and Telmatobacter bradus TPB6017(T) (95.0% identity), revealing that strain S55(T) should be classified within the phylum Acidobacteria, subdivision 1. Strain S55(T) is a rod-like bacterium that grows at acidic pH (3 to 6). Its phylogenetic, genotypic, phenotypic, and chemotaxonomic characteristics indicate that strain S55(T) corresponds to a new genus within the phylum Acidobacteria; thus, we propose the name Terracidiphilus gabretensis gen. nov., sp. nov. (strain S55(T) = NBRC 111238(T) = CECT 8791(T)). This strain produces extracellular enzymes implicated in the degradation of plant-derived biopolymers. Moreover, analysis of the genome sequence of strain S55(T) also reveals the presence of enzymatic machinery required for organic matter decomposition. Soil metatranscriptomic analyses found 132 genes from strain S55(T) being expressed in the forest soil, especially during winter. Our results suggest an important contribution of T. gabretensis S55(T) in the carbon cycle in the Picea abies coniferous forest.
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Affiliation(s)
- Paula García-Fraile
- Institute of Microbiology ASCR, Laboratory of Fungal Genetics and Metabolism, Prague, Czech Republic
| | - Oldrich Benada
- Institute of Microbiology ASCR, Laboratory of Molecular Structure Characterization, Prague, Czech Republic
| | - Tomáš Cajthaml
- Institute of Microbiology ASCR, Laboratory of Environmental Biotechnology, Prague, Czech Republic
| | - Petr Baldrian
- Institute of Microbiology ASCR, Laboratory of Environmental Microbiology, Prague, Czech Republic
| | - Salvador Lladó
- Institute of Microbiology ASCR, Laboratory of Environmental Microbiology, Prague, Czech Republic
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Lindner AS, Pacheco A, Aldrich HC, Costello Staniec A, Uz I, Hodson DJ. Methylocystis hirsuta sp. nov., a novel methanotroph isolated from a groundwater aquifer. Int J Syst Evol Microbiol 2007; 57:1891-1900. [PMID: 17684277 DOI: 10.1099/ijs.0.64541-0] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Strain CSC1T, a Gram-negative, aerobic, methane-oxidizing bacterium, was isolated from an uncontaminated aquifer nearly 20 years ago. Based on 16S rRNA gene sequence similarity, this strain was identified as a member of the Alphaproteobacteria, most closely related to an uncultured member of the Methylocystaceae as well as two cultured organisms, Methylocystis sp. L32 and Methylocystis sp. SC2. This strain differed from extant species in cell shape, size, expression of soluble methane monooxygenase and its unique spiny surface layers, composed of polysaccharide. DNA–DNA hybridization results showed only 3.8 % relatedness with Methylocystis echinoides NCIMB 13100 and 41.1 % relatedness with Methylocystis rosea SV97T. Based on these genotypic and physiological differences, this isolate is proposed as a member of a novel species of the genus Methylocystis, Methylocystis hirsuta sp. nov. (type strain CSC1T =ATCC BAA-1344T =DSM 18500T).
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Affiliation(s)
- Angela S Lindner
- Department of Environmental Engineering Sciences, University of Florida, Gainesville, FL 32611-6450, USA
| | - Adriana Pacheco
- Department of Environmental Engineering Sciences, University of Florida, Gainesville, FL 32611-6450, USA
| | - Henry C Aldrich
- Department of Microbiology and Cell Science, University of Florida, Gainesville, FL 32611-0700, USA
| | - Andria Costello Staniec
- Department of Civil and Environmental Engineering, Syracuse University, Syracuse, NY 13244-1240, USA
| | - Ilker Uz
- Department of Soil and Water Sciences, University of Florida, Gainesville, FL 32611-0290, USA
| | - David J Hodson
- Department of Environmental Engineering Sciences, University of Florida, Gainesville, FL 32611-6450, USA
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Krautgartner WD, Vitkov L. Visualization of neutrophil extracellular traps in TEM. Micron 2007; 39:367-72. [PMID: 17498964 DOI: 10.1016/j.micron.2007.03.007] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/25/2007] [Revised: 03/18/2007] [Accepted: 03/19/2007] [Indexed: 11/18/2022]
Abstract
Neutrophil extracellular traps (NETs) have recently been described as an important innate defence mechanism in inflammation. However, routine electron microscopic staining techniques faintly stain NETs and are therefore insufficient for enabling a distinction between these and the host cell debris as well as proteins regularly present at the site of inflammation. In order to test suitable electron microscopic staining techniques, NETs induced ex vivo via phorbol myristate were absorbed on formvar. Four types of drop-on-grid positive staining were used: osmium tetroxide (Os), osmium tetroxide-uranyl acetate-lead citrate (Os-U-Pb), ruthenium red-osmium tetroxide (RR-OsO4), and cuprolinic blue enhanced by sodium tungstate (CB-WO4). We observed no staining of NETs using Os, faint staining with Os-U-Pb, better but still weak staining with CB-WO4 and outstanding staining with RR-OsO4. Furthermore, RR-OsO4 staining also enables the observation of bacterial fimbriae-mediated adhesion, which is possibly responsible for the ability of NETs to bind bacteria. Thus, the offered RR-OsO4 staining technique may facilitate the study of the NETs-bacterial interactions.
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Affiliation(s)
- Wolf Dietrich Krautgartner
- Department of Light & Electron Microscopy, Organismic Biology, University of Salzburg, Hellbrunnerstrabe 34, A-5020 Salzburg, Austria
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Erlandsen SL, Kristich CJ, Dunny GM, Wells CL. High-resolution visualization of the microbial glycocalyx with low-voltage scanning electron microscopy: dependence on cationic dyes. J Histochem Cytochem 2004; 52:1427-35. [PMID: 15505337 PMCID: PMC3957825 DOI: 10.1369/jhc.4a6428.2004] [Citation(s) in RCA: 119] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
The microbial glycocalyx is composed of a variety of polyanionic exopolysaccharides and plays important roles in microbial attachment to different substrata and to other cells. Here we report the successful use of low-voltage scanning electron microscopy (LVSEM) to visualize the glycocalyx in two microbial models (Klebsiella pneumoniae and Enterococcus faecalis biofilms) at high resolution, and also the dependence on fixation containing polycationic dyes for its visualization. Fixation in a paraformaldehyde-glutaraldehyde cocktail without cationic dyes was inadequate for visualizing the glycocalyx, whereas addition of various dyes (alcian blue, safranin, and ruthenium red) to the aldehyde cocktail appeared necessary for stabilization. The cationic dyes varied in size, shape, and charge density, and these factors appeared responsible for different phenotypic appearances of the glycocalyx with each dye. These results suggest that aldehyde fixation with cationic dyes for high-resolution LVSEM will be a useful tool for investigation of microbial biofilms as well as investigation of the extent and role of the glycocalyx in microbial attachment to surfaces.
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Affiliation(s)
- Stanley L Erlandsen
- Deptartment of Genetics, University of Minnesota Medical School, Minneapolis, MN 55455, USA.
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Fassel TA, Edmiston CE. Bacterial biofilms: strategies for preparing glycocalyx for electron microscopy. Methods Enzymol 2001; 310:194-203. [PMID: 10547793 DOI: 10.1016/s0076-6879(99)10017-x] [Citation(s) in RCA: 35] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/21/2023]
Affiliation(s)
- T A Fassel
- Core Electron Microscope Unit, Scripps Research Institute, La Jolla, California 92037-1027, USA
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Abstract
Ruthenium red, a promising cationic reagent for electron microscopy (EM), has long been an important tool in histology. The reagent was initially used by botanists as a semispecific stain for pectic substances, but it has gradually been embraced by investigators in microbiology and the animal sciences as a stain for anionic glycosylated polymeric substances. Luft developed a reliable method and demonstrated that ruthenium red was a useful reagent for visualizing ultrastructural detail. Many investigators, using modifications of Luft's approach, have identified numerous applications for this important reagent. Ruthenium red has been used to show the ultrastructural detail of bacterial glycocalyces. Strong, sharp and consistent observations of this ultrastructural component of the bacterial cell have given a better understanding its fibrous anionic matrix. Any variations in staining owing to artifactual alteration of the fine delicate ultrastructural features have been overcome by incorporation of diamine lysine into ruthenium red methods, thus providing flexible processing times under less than ideal laboratory sampling conditions. Ruthenium red has broad utility in the biological sciences, and in combination with lysine, it is an excellent EM stain for enhanced visualization of bacterial glycocalyx from culture or from clinical specimens.
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Affiliation(s)
- T A Fassel
- Core Electron Microscope Unit, The Scripps Research Institute, La Jolla, California 92037, USA
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Davies DG, Parsek MR, Pearson JP, Iglewski BH, Costerton JW, Greenberg EP. The involvement of cell-to-cell signals in the development of a bacterial biofilm. Science 1998; 280:295-8. [PMID: 9535661 DOI: 10.1126/science.280.5361.295] [Citation(s) in RCA: 2090] [Impact Index Per Article: 80.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/02/2022]
Abstract
Bacteria in nature often exist as sessile communities called biofilms. These communities develop structures that are morphologically and physiologically differentiated from free-living bacteria. A cell-to-cell signal is involved in the development of Pseudomonas aeruginosa biofilms. A specific signaling mutant, a lasI mutant, forms flat, undifferentiated biofilms that unlike wild-type biofilms are sensitive to the biocide sodium dodecyl sulfate. Mutant biofilms appeared normal when grown in the presence of a synthetic signal molecule. The involvement of an intercellular signal molecule in the development of P. aeruginosa biofilms suggests possible targets to control biofilm growth on catheters, in cystic fibrosis, and in other environments where P. aeruginosa biofilms are a persistent problem.
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Affiliation(s)
- D G Davies
- Center for Biofilm Engineering, Montana State University, Bozeman, MT 59717-3980, USA
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Brown ML, Aldrich HC, Gauthier JJ. Relationship between glycocalyx and povidone-iodine resistance in Pseudomonas aeruginosa (ATCC 27853) biofilms. Appl Environ Microbiol 1995; 61:187-93. [PMID: 7887601 PMCID: PMC167274 DOI: 10.1128/aem.61.1.187-193.1995] [Citation(s) in RCA: 42] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023] Open
Abstract
Biofilm-embedded bacteria are generally more resistant to antimicrobial agents than are planktonic bacteria. Two possible mechanisms for biofilm resistance are that the glycocalyx matrix secreted by cells in a biofilm reacts with and neutralizes the antimicrobial agent and that the matrix creates a diffusion barrier to the antimicrobial agent. This study was therefore conducted to examine the relationship between glycocalyx and enhanced povidone-iodine resistance in biofilms of Pseudomonas aeruginosa (ATCC 27853). Biofilms were generated by inoculation of polycarbonate membranes with broth-grown cells and incubation of them on the surfaces of nutrient agar plates. The quantities of glycocalyx material per cell were found not to be significantly different between biofilm and planktonic samples. Transmission electron microscopy showed that the distributions of glycocalyx material around cells differed in biofilm and in planktonic samples. Addition of alginic acid to planktonic cell suspensions resulted in a slight increase in resistance to povidone-iodine, suggesting some neutralizing interaction. However, the iodine demands created by biofilm and planktonic samples of equivalent biomass were not significantly different and, therefore, do not explain the contrast in resistance observed between biofilm and planktonic samples. Examination of the relationship between cell death and biomass detachment from the glycocalyx matrix revealed that most cell death occurred in the fraction of biomass that detached from a biofilm during treatment. The overall rate of iodine diffusion through biofilms was not different from that of planktonic cells collected on a polycarbonate membrane.(ABSTRACT TRUNCATED AT 250 WORDS)
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Affiliation(s)
- M L Brown
- Department of Biology, University of Alabama at Birmingham 35294
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