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Biofilms: Extracellular Bastions of Bacteria
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Biofilms: Extracellular Bastions of Bacteria

A special issue of International Journal of Molecular Sciences (ISSN 1422-0067). This special issue belongs to the section "Biochemistry".

Deadline for manuscript submissions: closed (30 October 2013) | Viewed by 171411

Printed Edition Available!
A printed edition of this Special Issue is available here.

Special Issue Editor

Prof. Dr. Alan W. Decho

E-Mail Website
Guest Editor
Department of Environmental Health Sciences, Arnold School of Public Health, University of South Carolina, Columbia, SC 29208, USA
Interests: biofilms; extracellular polymers; microbial mats; chemical communication; infections; novel antibiotics; nano-based approaches to microbiology

Special Issue Information

Dear Colleagues,

Biofilms are attached forms of bacteria and other microorganisms enclosed in a matrix of extracellular polymeric substances (EPS), and comprise a microbial lifestyle that is quite different from that of free-living planktonic cells.  The biofilm state is now universally-recognized for its complexity and resiliency to stresses, and importance in natural environments, as well its roles in comensal flora and infection processes. However, the EPS matrix, which occur just ‘outside of cells’, is poorly understood, and has been understated in the literature. Yet this extracellular milieu is crucial to the functioning and resiliency of the biofilm. Recently, exciting new advances have emerged that are helping to understand the EPS matrix, its processes, ultrastructure, and importance to cells in nature and disease.

This special issue of IJMS will be devoted to original papers and reviews addressing biofilms with a special emphasis on the properties and processes occurring ‘outside of cells’ within the extracellular biome of EPS. These can emphasize:  (1) imaging approaches and nano-based tools used to explore microenvironments of EPS and cells;  (2) characterization  of molecules, and structures; 3) the localization by EPS of antibiotics, vesicles, extracellular-enzymes; chemical communication and sensing, and electron transfer via EPS nanowires; 4) the role of (extracellular) e-DNA and e-proteins, secreted sRNAs, enhanced gene exchange, and microspatial heterogeneity, and other EPS-related topics as well.

Dr. Alan W. Decho
Guest Editor

Submission

Manuscripts should be submitted online at www.mdpi.com by registering and logging in to this website. Once you are registered, click here to go to the submission form. Manuscripts can be submitted until the deadline. Papers will be published continuously (as soon as accepted) and will be listed together on the special issue website. Research articles, review articles as well as communications are invited. For planned papers, a title and short abstract (about 100 words) can be sent to the Editorial Office for announcement on this website.

Submitted manuscripts should not have been published previously, nor be under consideration for publication elsewhere (except conference proceedings papers). All manuscripts are refereed through a peer-review process. A guide for authors and other relevant information for submission of manuscripts is available on the Instructions for Authors page. International Journal of Molecular Sciences is an international peer-reviewed Open Access semimonthly journal published by MDPI.

Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 1600 CHF.

Keywords

  • biofilm
  • EPS (extracellular polymeric substances)
  • chemical communication
  • infections
  • microbial mats
  • imaging
  • nanoparticles
  • vesicles

Published Papers (16 papers)

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Editorial

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72 KiB  
Editorial
The EPS Matrix as an Adaptive Bastion for Biofilms: Introduction to Special Issue
by Alan W. Decho
Int. J. Mol. Sci. 2013, 14(12), 23297-23300; https://doi.org/10.3390/ijms141223297 - 26 Nov 2013
Cited by 7 | Viewed by 5134
Abstract
The process of biofilm formation has knowingly, and even unsuspectingly, baffled scientists for almost as long as the field of microbiology itself has existed. This Special Issue of the International Journal of Molecular Sciences (IJMS) specifically addresses an important component of the biofilm, [...] Read more.
The process of biofilm formation has knowingly, and even unsuspectingly, baffled scientists for almost as long as the field of microbiology itself has existed. This Special Issue of the International Journal of Molecular Sciences (IJMS) specifically addresses an important component of the biofilm, the extracellular matrix. This matrix forms the protective secretions that surround biofilm cells and afford a “built environment” to contain biofilm processes. During the earlier days of microbiology, it was intriguing to Claude ZoBell that attached bacteria sometimes were able to proliferate when their planktonic counterparts were unable to grow [1]. During the 1970s, this attached state was beginning to be explored [2], and it was realized to be anchored in a matrix of slime-like molecules. The slime-like matrix together with cells was to be called the “biofilm”, a term developed by the late Bill Costerton, Bill Characklis and colleagues. The scientific revelation that attached bacteria were different from free (i.e., planktonic) cells in their physiological behavior and adaptability, launched an era of focused exploration in this area of microbiology. It was initially surprising, though not unexpected in retrospect, that interest in biofilms has grown and now infiltrates virtually all aspects of our scientific study. Since that time there has been a near-exponential growth in the numbers of scientific publications addressing biofilms owing to their immediate relevance to ecology, biotechnology, health and industry. [...] Full article
(This article belongs to the Special Issue Biofilms: Extracellular Bastions of Bacteria)

Research

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1696 KiB  
Article
Three-Dimensional Stratification of Bacterial Biofilm Populations in a Moving Bed Biofilm Reactor for Nitritation-Anammox
by Robert Almstrand, Frank Persson, Holger Daims, Maria Ekenberg, Magnus Christensson, Britt-Marie Wilén, Fred Sörensson and Malte Hermansson
Int. J. Mol. Sci. 2014, 15(2), 2191-2206; https://doi.org/10.3390/ijms15022191 - 29 Jan 2014
Cited by 50 | Viewed by 9466
Abstract
Moving bed biofilm reactors (MBBRs) are increasingly used for nitrogen removal with nitritation-anaerobic ammonium oxidation (anammox) processes in wastewater treatment. Carriers provide protected surfaces where ammonia oxidizing bacteria (AOB) and anammox bacteria form complex biofilms. However, the knowledge about the organization of microbial [...] Read more.
Moving bed biofilm reactors (MBBRs) are increasingly used for nitrogen removal with nitritation-anaerobic ammonium oxidation (anammox) processes in wastewater treatment. Carriers provide protected surfaces where ammonia oxidizing bacteria (AOB) and anammox bacteria form complex biofilms. However, the knowledge about the organization of microbial communities in MBBR biofilms is sparse. We used new cryosectioning and imaging methods for fluorescence in situ hybridization (FISH) to study the structure of biofilms retrieved from carriers in a nitritation-anammox MBBR. The dimensions of the carrier compartments and the biofilm cryosections after FISH showed good correlation, indicating little disturbance of biofilm samples by the treatment. FISH showed that Nitrosomonas europaea/eutropha-related cells dominated the AOB and Candidatus Brocadia fulgida-related cells dominated the anammox guild. New carriers were initially colonized by AOB, followed by anammox bacteria proliferating in the deeper biofilm layers, probably in anaerobic microhabitats created by AOB activity. Mature biofilms showed a pronounced three-dimensional stratification where AOB dominated closer to the biofilm-water interface, whereas anammox were dominant deeper into the carrier space and towards the walls. Our results suggest that current mathematical models may be oversimplifying these three-dimensional systems and unless the multidimensionality of these systems is considered, models may result in suboptimal design of MBBR carriers. Full article
(This article belongs to the Special Issue Biofilms: Extracellular Bastions of Bacteria)
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1101 KiB  
Article
Changing Microspatial Patterns of Sulfate-Reducing Microorganisms (SRM) during Cycling of Marine Stromatolite Mats
by Alexandru I. Petrisor, Sandra Szyjka, Tomohiro Kawaguchi, Pieter T. Visscher, Robert Sean Norman and Alan W. Decho
Int. J. Mol. Sci. 2014, 15(1), 850-877; https://doi.org/10.3390/ijms15010850 - 09 Jan 2014
Cited by 6 | Viewed by 7513
Abstract
Microspatial arrangements of sulfate-reducing microorganisms (SRM) in surface microbial mats (~1.5 mm) forming open marine stromatolites were investigated. Previous research revealed three different mat types associated with these stromatolites, each with a unique petrographic signature. Here we focused on comparing “non-lithifying” (Type-1) and [...] Read more.
Microspatial arrangements of sulfate-reducing microorganisms (SRM) in surface microbial mats (~1.5 mm) forming open marine stromatolites were investigated. Previous research revealed three different mat types associated with these stromatolites, each with a unique petrographic signature. Here we focused on comparing “non-lithifying” (Type-1) and “lithifying” (Type-2) mats. Our results revealed three major trends: (1) Molecular typing using the dsrA probe revealed a shift in the SRM community composition between Type-1 and Type-2 mats. Fluorescence in-situ hybridization (FISH) coupled to confocal scanning-laser microscopy (CSLM)-based image analyses, and 35SO42−-silver foil patterns showed that SRM were present in surfaces of both mat types, but in significantly (p < 0.05) higher abundances in Type-2 mats. Over 85% of SRM cells in the top 0.5 mm of Type-2 mats were contained in a dense 130 µm thick horizontal layer comprised of clusters of varying sizes; (2) Microspatial mapping revealed that locations of SRM and CaCO3 precipitation were significantly correlated (p < 0.05); (3) Extracts from Type-2 mats contained acylhomoserine-lactones (C4- ,C6- ,oxo-C6,C7- ,C8- ,C10- ,C12- , C14-AHLs) involved in cell-cell communication. Similar AHLs were produced by SRM mat-isolates. These trends suggest that development of a microspatially-organized SRM community is closely-associated with the hallmark transition of stromatolite surface mats from a non-lithifying to a lithifying state. Full article
(This article belongs to the Special Issue Biofilms: Extracellular Bastions of Bacteria)
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2442 KiB  
Article
Biofilms’ Role in Planktonic Cell Proliferation
by Elanna Bester, Gideon M. Wolfaardt, Nahid B. Aznaveh and Jesse Greener
Int. J. Mol. Sci. 2013, 14(11), 21965-21982; https://doi.org/10.3390/ijms141121965 - 06 Nov 2013
Cited by 35 | Viewed by 6994
Abstract
The detachment of single cells from biofilms is an intrinsic part of this surface-associated mode of bacterial existence. Pseudomonas sp. strain CT07gfp biofilms, cultivated in microfluidic channels under continuous flow conditions, were subjected to a range of liquid shear stresses (9.42 mPa [...] Read more.
The detachment of single cells from biofilms is an intrinsic part of this surface-associated mode of bacterial existence. Pseudomonas sp. strain CT07gfp biofilms, cultivated in microfluidic channels under continuous flow conditions, were subjected to a range of liquid shear stresses (9.42 mPa to 320 mPa). The number of detached planktonic cells was quantified from the effluent at 24-h intervals, while average biofilm thickness and biofilm surface area were determined by confocal laser scanning microscopy and image analysis. Biofilm accumulation proceeded at the highest applied shear stress, while similar rates of planktonic cell detachment was maintained for biofilms of the same age subjected to the range of average shear rates. The conventional view of liquid-mediated shear leading to the passive erosion of single cells from the biofilm surface, disregards the active contribution of attached cell metabolism and growth to the observed detachment rates. As a complement to the conventional conceptual biofilm models, the existence of a biofilm surface-associated zone of planktonic cell proliferation is proposed to highlight the need to expand the traditional perception of biofilms as promoting microbial survival, to include the potential of biofilms to contribute to microbial proliferation. Full article
(This article belongs to the Special Issue Biofilms: Extracellular Bastions of Bacteria)
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478 KiB  
Article
Systematic Exploration of Natural and Synthetic Flavonoids for the Inhibition of Staphylococcus aureus Biofilms
by Suvi Manner, Malena Skogman, Darla Goeres, Pia Vuorela and Adyary Fallarero
Int. J. Mol. Sci. 2013, 14(10), 19434-19451; https://doi.org/10.3390/ijms141019434 - 25 Sep 2013
Cited by 89 | Viewed by 11921
Abstract
When single-cell (or suspended) bacteria switch into the biofilm lifestyle, they become less susceptible to antimicrobials, imposing the need for anti-biofilms research. Flavonoids are among the most extensively studied natural compounds with an unprecedented amount of bioactivity claims. Most studies focus on the [...] Read more.
When single-cell (or suspended) bacteria switch into the biofilm lifestyle, they become less susceptible to antimicrobials, imposing the need for anti-biofilms research. Flavonoids are among the most extensively studied natural compounds with an unprecedented amount of bioactivity claims. Most studies focus on the antibacterial effects against suspended cells; fewer reports have researched their anti-biofilm properties. Here, a high throughput phenotypic platform was utilized to screen for the inhibitory activity of 500 flavonoids, including natural and synthetic derivatives, against Staphylococcus aureus biofilms. Since discrepancies among results from earlier antibacterial studies on flavonoids had been noted, the current study aimed to minimize sources of variations. After the first screen, flavonoids were classified as inactive (443), moderately active (47) or highly active (10). Further, exclusion criteria combining bioactivity and selectivity identified two synthetic flavans as the most promising. The body of data reported here serves three main purposes. First, it offers an improved methodological workflow for anti-biofilm screens of chemical libraries taking into account the (many times ignored) connections between anti-biofilm and antibacterial properties. This is particularly relevant for the study of flavonoids and other natural products. Second, it provides a large and freely available anti-biofilm bioactivity dataset that expands the knowledge on flavonoids and paves the way for future structure-activity relationship studies and structural optimizations. Finally, it identifies two new flavans that can successfully act on biofilms, as well as on suspended bacteria and represent more feasible antibacterial candidates. Full article
(This article belongs to the Special Issue Biofilms: Extracellular Bastions of Bacteria)
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318 KiB  
Article
Emulsifying Activity and Stability of a Non-Toxic Bioemulsifier Synthesized by Microbacterium sp. MC3B-10
by Juan Carlos Camacho-Chab, Jean Guézennec, Manuel Jesús Chan-Bacab, Elvira Ríos-Leal, Corinne Sinquin, Raquel Muñiz-Salazar, Susana Del C. De la Rosa-García, Manuela Reyes-Estebanez and Benjamín Otto Ortega-Morales
Int. J. Mol. Sci. 2013, 14(9), 18959-18972; https://doi.org/10.3390/ijms140918959 - 13 Sep 2013
Cited by 52 | Viewed by 9184
Abstract
A previously reported bacterial bioemulsifier, here termed microbactan, was further analyzed to characterize its lipid component, molecular weight, ionic character and toxicity, along with its bioemulsifying potential for hydrophobic substrates at a range of temperatures, salinities and pH values. Analyses showed that microbactan [...] Read more.
A previously reported bacterial bioemulsifier, here termed microbactan, was further analyzed to characterize its lipid component, molecular weight, ionic character and toxicity, along with its bioemulsifying potential for hydrophobic substrates at a range of temperatures, salinities and pH values. Analyses showed that microbactan is a high molecular weight (700 kDa), non-ionic molecule. Gas chromatography of the lipid fraction revealed the presence of palmitic, stearic, and oleic acids; thus microbactan may be considered a glycolipoprotein. Microbactan emulsified aromatic hydrocarbons and oils to various extents; the highest emulsification index was recorded against motor oil (96%). The stability of the microbactan-motor oil emulsion model reached its highest level (94%) at 50 °C, pH 10 and 3.5% NaCl content. It was not toxic to Artemia salina nauplii. Microbactan is, therefore, a non-toxic and non-ionic bioemulsifier of high molecular weight with affinity for a range of oily substrates. Comparative phylogenetic assessment of the 16S rDNA gene of Microbacterium sp. MC3B-10 with genes derived from other marine Microbacterium species suggested that this genus is well represented in coastal zones. The chemical nature and stability of the bioemulsifier suggest its potential application in bioremediation of marine environments and in cosmetics. Full article
(This article belongs to the Special Issue Biofilms: Extracellular Bastions of Bacteria)
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217 KiB  
Short Note
Interactions between Lactobacillus crispatus and Bacterial Vaginosis (BV)-Associated Bacterial Species in Initial Attachment and Biofilm Formation
by António Machado, Kimberly Kay Jefferson and Nuno Cerca
Int. J. Mol. Sci. 2013, 14(6), 12004-12012; https://doi.org/10.3390/ijms140612004 - 05 Jun 2013
Cited by 80 | Viewed by 10654
Abstract
Certain anaerobic bacterial species tend to predominate the vaginal flora during bacterial vaginosis (BV), with Gardnerella vaginalis being the most common. However, the exact role of G. vaginalis in BV has not yet been determined. The main goal of this study was to [...] Read more.
Certain anaerobic bacterial species tend to predominate the vaginal flora during bacterial vaginosis (BV), with Gardnerella vaginalis being the most common. However, the exact role of G. vaginalis in BV has not yet been determined. The main goal of this study was to test the hypothesis that G. vaginalis is an early colonizer, paving the way for intermediate (e.g., Fusobacterium nucleatum) and late colonizers (e.g., Prevotella bivia). Theoretically, in order to function as an early colonizer, species would need to be able to adhere to vaginal epithelium, even in the presence of vaginal lactobacilli. Therefore, we quantified adherence of G. vaginalis and other BV-associated bacteria to an inert surface pre-coated with Lactobacillus crispatus using a new Peptide Nucleic Acid (PNA) Fluorescence In Situ Hybridization (FISH) methodology. We found that G. vaginalis had the greatest capacity to adhere in the presence of L. crispatus. Theoretically, an early colonizer would contribute to the adherence and/or growth of additional species, so we next quantified the effect of G. vaginalis biofilms on the adherence and growth of other BV-associated species by quantitative Polymerase Chain Reaction (qPCR) technique. Interestingly, G. vaginalis derived a growth benefit from the addition of a second species, regardless of the species. Conversely, G. vaginalis biofilms enhanced the growth of P. bivia, and to a minor extent of F. nucleatum. These results contribute to our understanding of BV biofilm formation and the progression of the disorder. Full article
(This article belongs to the Special Issue Biofilms: Extracellular Bastions of Bacteria)
616 KiB  
Article
The Interaction of CuS and Halothiobacillus HT1 Biofilm in Microscale Using Synchrotron Radiation-Based Techniques
by Huirong Lin, Guangcun Chen, Shenhai Zhu, Yingxu Chen, Dongliang Chen, Wei Xu, Xiaohan Yu and Jiyan Shi
Int. J. Mol. Sci. 2013, 14(6), 11113-11124; https://doi.org/10.3390/ijms140611113 - 24 May 2013
Cited by 9 | Viewed by 7145
Abstract
In order to investigate the microbe-mineral interaction in the micro scale, spatial distribution and speciation of Cu and S in Halothiobacillus HT1 biofilm formed on a CuS surface was examined using synchrotron-based X-ray techniques. Confocal laser scanning microscope (CLSM) results indicated that Halothiobacillus [...] Read more.
In order to investigate the microbe-mineral interaction in the micro scale, spatial distribution and speciation of Cu and S in Halothiobacillus HT1 biofilm formed on a CuS surface was examined using synchrotron-based X-ray techniques. Confocal laser scanning microscope (CLSM) results indicated that Halothiobacillus HT1 biofilm formation gave rise to distinct chemical and redox gradients, leading to diverse niches in the biofilm. Live cells were distributed at the air-biofilm and membrane-biofilm interface. CuS was oxidized by Halothiobacillus HT1 biofilm, and copper penetrated into the biofilm. Sulfide was oxidized to cysteine (77.3%), sulfite (3.8%) and sulfonate (18.9%). Cu-cysteine-like species were involved in the copper homeostasis. These results significantly improve our understanding of the interfacial properties of the biofilm-mineral interface. Full article
(This article belongs to the Special Issue Biofilms: Extracellular Bastions of Bacteria)
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Review

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335 KiB  
Review
Enhancing Metagenomics Investigations of Microbial Interactions with Biofilm Technology
by Robert J. C. McLean and Kavita S. Kakirde
Int. J. Mol. Sci. 2013, 14(11), 22246-22257; https://doi.org/10.3390/ijms141122246 - 11 Nov 2013
Cited by 18 | Viewed by 7257
Abstract
Investigations of microbial ecology and diversity have been greatly enhanced by the application of culture-independent techniques. One such approach, metagenomics, involves sample collections from soil, water, and other environments. Extracted nucleic acids from bulk environmental samples are sequenced and analyzed, which allows microbial [...] Read more.
Investigations of microbial ecology and diversity have been greatly enhanced by the application of culture-independent techniques. One such approach, metagenomics, involves sample collections from soil, water, and other environments. Extracted nucleic acids from bulk environmental samples are sequenced and analyzed, which allows microbial interactions to be inferred on the basis of bioinformatics calculations. In most environments, microbial interactions occur predominately in surface-adherent, biofilm communities. In this review, we address metagenomics sampling and biofilm biology, and propose an experimental strategy whereby the resolving power of metagenomics can be enhanced by incorporating a biofilm-enrichment step during sample acquisition. Full article
(This article belongs to the Special Issue Biofilms: Extracellular Bastions of Bacteria)
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1494 KiB  
Review
Biofilms: The Stronghold of Legionella pneumophila
by Mena Abdel-Nour, Carla Duncan, Donald E. Low and Cyril Guyard
Int. J. Mol. Sci. 2013, 14(11), 21660-21675; https://doi.org/10.3390/ijms141121660 - 31 Oct 2013
Cited by 114 | Viewed by 14164
Abstract
Legionellosis is mostly caused by Legionella pneumophila and is defined as a severe respiratory illness with a case fatality rate ranging from 5% to 80%. L. pneumophila is ubiquitous in natural and anthropogenic water systems. L. pneumophila is transmitted by inhalation of contaminated [...] Read more.
Legionellosis is mostly caused by Legionella pneumophila and is defined as a severe respiratory illness with a case fatality rate ranging from 5% to 80%. L. pneumophila is ubiquitous in natural and anthropogenic water systems. L. pneumophila is transmitted by inhalation of contaminated aerosols produced by a variety of devices. While L. pneumophila replicates within environmental protozoa, colonization and persistence in its natural environment are also mediated by biofilm formation and colonization within multispecies microbial communities. There is now evidence that some legionellosis outbreaks are correlated with the presence of biofilms. Thus, preventing biofilm formation appears as one of the strategies to reduce water system contamination. However, we lack information about the chemical and biophysical conditions, as well as the molecular mechanisms that allow the production of biofilms by L. pneumophila. Here, we discuss the molecular basis of biofilm formation by L. pneumophila and the roles of other microbial species in L. pneumophila biofilm colonization. In addition, we discuss the protective roles of biofilms against current L. pneumophila sanitation strategies along with the initial data available on the regulation of L. pneumophila biofilm formation. Full article
(This article belongs to the Special Issue Biofilms: Extracellular Bastions of Bacteria)
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683 KiB  
Review
Biofilm Matrix and Its Regulation in Pseudomonas aeruginosa
by Qing Wei and Luyan Z. Ma
Int. J. Mol. Sci. 2013, 14(10), 20983-21005; https://doi.org/10.3390/ijms141020983 - 18 Oct 2013
Cited by 236 | Viewed by 20373
Abstract
Biofilms are communities of microorganisms embedded in extracellular polymeric substances (EPS) matrix. Bacteria in biofilms demonstrate distinct features from their free-living planktonic counterparts, such as different physiology and high resistance to immune system and antibiotics that render biofilm a source of chronic and [...] Read more.
Biofilms are communities of microorganisms embedded in extracellular polymeric substances (EPS) matrix. Bacteria in biofilms demonstrate distinct features from their free-living planktonic counterparts, such as different physiology and high resistance to immune system and antibiotics that render biofilm a source of chronic and persistent infections. A deeper understanding of biofilms will ultimately provide insights into the development of alternative treatment for biofilm infections. The opportunistic pathogen Pseudomonas aeruginosa, a model bacterium for biofilm research, is notorious for its ability to cause chronic infections by its high level of drug resistance involving the formation of biofilms. In this review, we summarize recent advances in biofilm formation, focusing on the biofilm matrix and its regulation in P. aeruginosa, aiming to provide resources for the understanding and control of bacterial biofilms. Full article
(This article belongs to the Special Issue Biofilms: Extracellular Bastions of Bacteria)
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3656 KiB  
Review
Marine Polysaccharide Networks and Diatoms at the Nanometric Scale
by Vesna Svetličić, Vera Žutić, Galja Pletikapić and Tea Mišić Radić
Int. J. Mol. Sci. 2013, 14(10), 20064-20078; https://doi.org/10.3390/ijms141020064 - 09 Oct 2013
Cited by 28 | Viewed by 8813
Abstract
Despite many advances in research on photosynthetic carbon fixation in marine diatoms, the biophysical and biochemical mechanisms of extracellular polysaccharide production remain significant challenges to be resolved at the molecular scale in order to proceed toward an understanding of their functions at the [...] Read more.
Despite many advances in research on photosynthetic carbon fixation in marine diatoms, the biophysical and biochemical mechanisms of extracellular polysaccharide production remain significant challenges to be resolved at the molecular scale in order to proceed toward an understanding of their functions at the cellular level, as well as their interactions and fate in the ocean. This review covers studies of diatom extracellular polysaccharides using atomic force microscopy (AFM) imaging and the quantification of physical forces. Following a brief summary of the basic principle of the AFM experiment and the first AFM studies of diatom extracellular polymeric substance (EPS), we focus on the detection of supramolecular structures in polysaccharide systems produced by marine diatoms. Extracellular polysaccharide fibrils, attached to the diatom cell wall or released into the surrounding seawater, form distinct supramolecular assemblies best described as gel networks. AFM makes characterization of the diatom polysaccharide networks at the micro and nanometric scales and a clear distinction between the self-assembly and self-organization of these complex systems in marine environments possible. Full article
(This article belongs to the Special Issue Biofilms: Extracellular Bastions of Bacteria)
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422 KiB  
Review
Archaeal Diversity in Biofilm Technologies Applied to Treat Urban and Industrial Wastewater: Recent Advances and Future Prospects
by Kadiya Calderón, Alejandro González-Martínez, Cinta Gómez-Silván, Francisco Osorio, Belén Rodelas and Jesús González-López
Int. J. Mol. Sci. 2013, 14(9), 18572-18598; https://doi.org/10.3390/ijms140918572 - 09 Sep 2013
Cited by 31 | Viewed by 11235
Abstract
Biological wastewater treatment (WWT) frequently relies on biofilms for the removal of anthropogenic contaminants. The use of inert carrier materials to support biofilm development is often required, although under certain operating conditions microorganisms yield structures called granules, dense aggregates of self-immobilized cells with [...] Read more.
Biological wastewater treatment (WWT) frequently relies on biofilms for the removal of anthropogenic contaminants. The use of inert carrier materials to support biofilm development is often required, although under certain operating conditions microorganisms yield structures called granules, dense aggregates of self-immobilized cells with the characteristics of biofilms maintained in suspension. Molecular techniques have been successfully applied in recent years to identify the prokaryotic communities inhabiting biofilms in WWT plants. Although methanogenic Archaea are widely acknowledged as key players for the degradation of organic matter in anaerobic bioreactors, other biotechnological functions fulfilled by Archaea are less explored, and research on their significance and potential for WWT is largely needed. In addition, the occurrence of biofilms in WWT plants can sometimes be a source of operational problems. This is the case for membrane bioreactors (MBR), an advanced technology that combines conventional biological treatment with membrane filtration, which is strongly limited by biofouling, defined as the undesirable accumulation of microbial biofilms and other materials on membrane surfaces. The prevalence and spatial distribution of archaeal communities in biofilm-based WWT as well as their role in biofouling are reviewed here, in order to illustrate the significance of this prokaryotic cellular lineage in engineered environments devoted to WWT. Full article
(This article belongs to the Special Issue Biofilms: Extracellular Bastions of Bacteria)
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194 KiB  
Review
Novel Strategies for the Prevention and Treatment of Biofilm Related Infections
by Meng Chen, Qingsong Yu and Hongmin Sun
Int. J. Mol. Sci. 2013, 14(9), 18488-18501; https://doi.org/10.3390/ijms140918488 - 06 Sep 2013
Cited by 330 | Viewed by 14405
Abstract
Biofilm formation by human bacterial pathogens on implanted medical devices causes major morbidity and mortality among patients, and leads to billions of dollars in healthcare cost. Biofilm is a complex bacterial community that is highly resistant to antibiotics and human immunity. As a [...] Read more.
Biofilm formation by human bacterial pathogens on implanted medical devices causes major morbidity and mortality among patients, and leads to billions of dollars in healthcare cost. Biofilm is a complex bacterial community that is highly resistant to antibiotics and human immunity. As a result, novel therapeutic solutions other than the conventional antibiotic therapies are in urgent need. In this review, we will discuss the recent research in discovery of alternative approaches to prevent or treat biofilms. Current anti-biofilm technologies could be divided into two groups. The first group focuses on targeting the biofilm forming process of bacteria based on our understanding of the molecular mechanism of biofilm formation. Small molecules and enzymes have been developed to inhibit or disrupt biofilm formation. Another group of anti-biofilm technologies focuses on modifying the biomaterials used in medical devices to make them resistant to biofilm formation. While these novel anti-biofilm approaches are still in nascent phases of development, efforts devoted to these technologies could eventually lead to anti-biofilm therapies that are superior to the current antibiotic treatment. Full article
(This article belongs to the Special Issue Biofilms: Extracellular Bastions of Bacteria)
287 KiB  
Review
Environmental Stimuli Shape Biofilm Formation and the Virulence of Periodontal Pathogens
by Marja T. Pöllänen, Annamari Paino and Riikka Ihalin
Int. J. Mol. Sci. 2013, 14(8), 17221-17237; https://doi.org/10.3390/ijms140817221 - 20 Aug 2013
Cited by 26 | Viewed by 8754
Abstract
Periodontitis is a common inflammatory disease affecting the tooth-supporting structures. It is initiated by bacteria growing as a biofilm at the gingival margin, and communication of the biofilms differs in health and disease. The bacterial composition of periodontitis-associated biofilms has been well documented [...] Read more.
Periodontitis is a common inflammatory disease affecting the tooth-supporting structures. It is initiated by bacteria growing as a biofilm at the gingival margin, and communication of the biofilms differs in health and disease. The bacterial composition of periodontitis-associated biofilms has been well documented and is under continual investigation. However, the roles of several host response and inflammation driven environmental stimuli on biofilm formation is not well understood. This review article addresses the effects of environmental factors such as pH, temperature, cytokines, hormones, and oxidative stress on periodontal biofilm formation and bacterial virulence. Full article
(This article belongs to the Special Issue Biofilms: Extracellular Bastions of Bacteria)
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300 KiB  
Review
The Role of Bacterial Biofilms and Surface Components in Plant-Bacterial Associations
by Pablo C. Bogino, María De las Mercedes Oliva, Fernando G. Sorroche and Walter Giordano
Int. J. Mol. Sci. 2013, 14(8), 15838-15859; https://doi.org/10.3390/ijms140815838 - 30 Jul 2013
Cited by 334 | Viewed by 17360
Abstract
The role of bacterial surface components in combination with bacterial functional signals in the process of biofilm formation has been increasingly studied in recent years. Plants support a diverse array of bacteria on or in their roots, transport vessels, stems, and leaves. These [...] Read more.
The role of bacterial surface components in combination with bacterial functional signals in the process of biofilm formation has been increasingly studied in recent years. Plants support a diverse array of bacteria on or in their roots, transport vessels, stems, and leaves. These plant-associated bacteria have important effects on plant health and productivity. Biofilm formation on plants is associated with symbiotic and pathogenic responses, but how plants regulate such associations is unclear. Certain bacteria in biofilm matrices have been found to induce plant growth and to protect plants from phytopathogens (a process termed biocontrol), whereas others are involved in pathogenesis. In this review, we systematically describe the various components and mechanisms involved in bacterial biofilm formation and attachment to plant surfaces and the relationships of these mechanisms to bacterial activity and survival. Full article
(This article belongs to the Special Issue Biofilms: Extracellular Bastions of Bacteria)
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