Electrical Methods Of Controlling Bacterial Adhesion And Biofilm On Device Surfaces Pdf
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- Magnetically driven active topography for long-term biofilm control
- Beyond Risk: Bacterial Biofilms and Their Regulating Approaches
- Electrical methods of controlling bacterial adhesion and biofilm on device surfaces.
E-mail: xhzhao gmail. Foodborne pathogens are the main factors behind foodborne diseases and food poisoning and thus pose a great threat to food safety.
Magnetically driven active topography for long-term biofilm control
Note 1: A biofilm is a system that can be adapted internally to environmental conditions by its inhabitants. A biofilm comprises any syntrophic consortium of microorganisms in which cells stick to each other and often also to a surface. Biofilms may form on living or non-living surfaces and can be prevalent in natural, industrial, and hospital settings. Microbes form a biofilm in response to a number of different factors,  which may include cellular recognition of specific or non-specific attachment sites on a surface, nutritional cues, or in some cases, by exposure of planktonic cells to sub-inhibitory concentrations of antibiotics.
A biofilm may also be considered a hydrogel , which is a complex polymer that contains many times its dry weight in water. Biofilms are not just bacterial slime layers but biological systems; the bacteria organize themselves into a coordinated functional community.
Biofilms can attach to a surface such as a tooth, rock, or surface, and may include a single species or a diverse group of microorganisms. The biofilm bacteria can share nutrients and are sheltered from harmful factors in the environment, such as desiccation, antibiotics, and a host body's immune system. A biofilm usually begins to form when a free-swimming bacterium attaches to a surface. Biofilms are hypothesised to have arisen during primitive Earth as a defence mechanism for prokaryotes, as the conditions at that time were too harsh for their survival.
Biofilms protect prokaryotic cells by providing them with homeostasis, encouraging the development of complex interactions between the cells in the biofilm. The formation of a biofilm begins with the attachment of free-floating microorganisms to a surface. A unique group of Archaea that inhabit anoxic groundwater have similar structures called hami. Each hamus is a long tube with three hook attachments that are used to attach to each other or to a surface, enabling a community to develop.
Hydrophobicity can also affect the ability of bacteria to form biofilms. Bacteria with increased hydrophobicity have reduced repulsion between the substratum and the bacterium. Non-motile bacteria cannot recognize surfaces or aggregate together as easily as motile bacteria. During surface colonization bacteria cells are able to communicate using quorum sensing QS products such as N-acyl homoserine lactone AHL. Once colonization has begun, the biofilm grows by a combination of cell division and recruitment.
Polysaccharide matrices typically enclose bacterial biofilms. In addition to the polysaccharides, these matrices may also contain material from the surrounding environment, including but not limited to minerals, soil particles, and blood components, such as erythrocytes and fibrin. The development of a biofilm may allow for an aggregate cell colony or colonies to be increasingly tolerant  or resistant to antibiotics.
Cell-cell communication or quorum sensing has been shown to be involved in the formation of biofilm in several bacterial species. Biofilms are the product of a microbial developmental process. Dispersal of cells from the biofilm colony is an essential stage of the biofilm life cycle.
Dispersal enables biofilms to spread and colonize new surfaces. Enzymes that degrade the biofilm extracellular matrix , such as dispersin B and deoxyribonuclease , may contribute to biofilm dispersal. Secreted by Pseudomonas aeruginosa , this compound induces cyclo heteromorphic cells in several species of bacteria and the yeast Candida albicans. Nitric oxide has potential as a treatment for patients that suffer from chronic infections caused by biofilms.
It was generally assumed that cells dispersed from biofilms immediately go into the planktonic growth phase. However, studies have shown that the physiology of dispersed cells from Pseudomonas aeruginosa biofilms is highly different from those of planktonic and biofilm cells. Dispersed cells are found to be highly virulent against macrophages and Caenorhabditis elegans , but highly sensitive towards iron stress, as compared with planktonic cells.
Biofilms are usually found on solid substrates submerged in or exposed to an aqueous solution , although they can form as floating mats on liquid surfaces and also on the surface of leaves, particularly in high humidity climates.
Given sufficient resources for growth, a biofilm will quickly grow to be macroscopic visible to the naked eye. Biofilms can contain many different types of microorganism, e. However, some organisms will form single-species films under certain conditions.
The EPS matrix consists of exopolysaccharides , proteins and nucleic acids. This matrix encases the cells within it and facilitates communication among them through biochemical signals as well as gene exchange. The EPS matrix also traps extracellular enzymes and keeps them in close proximity to the cells. Thus, the matrix represents an external digestion system and allows for stable synergistic microconsortia of different species.
Bacteria living in a biofilm usually have significantly different properties from free-floating bacteria of the same species, as the dense and protected environment of the film allows them to cooperate and interact in various ways. However, biofilms are not always less susceptible to antibiotics. For instance, the biofilm form of Pseudomonas aeruginosa has no greater resistance to antimicrobials than do stationary-phase planktonic cells, although when the biofilm is compared to logarithmic-phase planktonic cells, the biofilm does have greater resistance to antimicrobials.
This resistance to antibiotics in both stationary-phase cells and biofilms may be due to the presence of persister cells.
Biofilms are ubiquitous in organic life. Nearly every species of microorganism have mechanisms by which they can adhere to surfaces and to each other. Biofilms will form on virtually every non-shedding surface in non-sterile aqueous or humid environments. Biofilms can grow in the most extreme environments: from, for example, the extremely hot, briny waters of hot springs ranging from very acidic to very alkaline, to frozen glaciers.
Biofilms can be found on rocks and pebbles at the bottoms of most streams or rivers and often form on the surfaces of stagnant pools of water. Biofilms are important components of food chains in rivers and streams and are grazed by the aquatic invertebrates upon which many fish feed. Biofilms are found on the surface of and inside plants.
They can either contribute to crop disease or, as in the case of nitrogen-fixing rhizobia on root nodules , exist symbiotically with the plant. Percolating filters in sewage treatment works are highly effective removers of pollutants from settled sewage liquor. They work by trickling the liquid over a bed of hard material which is designed to have a very large surface area. A complex bio-film develops on the surface of the medium which absorbs, adsorbs and metabolises the pollutants.
The biofilm grows rapidly and when it becomes too thick to retain its grip on the media it washes off and is replaced by newly grown film. The washed off "sloughed" off film is settled out of the liquid stream to leave a highly purified effluent. Slow sand filters are used in water purification for treating raw water to produce a potable product.
They work through the formation of a biofilm called the hypogeal layer or Schmutzdecke in the top few millimetres of the fine sand layer. The Schmutzdecke is formed in the first 10—20 days of operation  and consists of bacteria , fungi , protozoa , rotifera and a range of aquatic insect larvae.
As an epigeal biofilm ages, more algae tend to develop and larger aquatic organisms may be present including some bryozoa , snails and Annelid worms. The surface biofilm is the layer that provides the effective purification in potable water treatment, the underlying sand providing the support medium for this biological treatment layer.
As water passes through the hypogeal layer, particles of foreign matter are trapped in the mucilaginous matrix and soluble organic material is adsorbed.
The contaminants are metabolised by the bacteria, fungi and protozoa. Plant-beneficial microbes can be categorized as plant growth-promoting rhizobacteria. Molecular properties on the surface of the bacterium cause an immune response in the plant host. Plants that have been colonized by PGPR forming a biofilm have gained systemic resistances and are primed for defense against pathogens.
Studies in discovered that the immune system supports biofilm development in the large intestine. This was supported mainly with the fact that the two most abundantly produced molecules by the immune system also support biofilm production and are associated with the biofilms developed in the gut.
This is especially important because the appendix holds a mass amount of these bacterial biofilms. In the human environment, biofilms can grow in showers very easily since they provide a moist and warm environment for the biofilm to thrive. Biofilms can form inside water and sewage pipes and cause clogging and corrosion.
Biofilms on floors and counters can make sanitation difficult in food preparation areas. Biofilm in soil can cause bioclogging. Biofilms in cooling- or heating-water systems are known to reduce heat transfer. Bacterial adhesion to boat hulls serves as the foundation for biofouling of seagoing vessels. Once a film of bacteria forms, it is easier for other marine organisms such as barnacles to attach. Time in dry dock for refitting and repainting reduces the productivity of shipping assets, and the useful life of ships is also reduced due to corrosion and mechanical removal scraping of marine organisms from ships' hulls.
Stromatolites are layered accretionary structures formed in shallow water by the trapping, binding and cementation of sedimentary grains by microbial biofilms, especially of cyanobacteria. Stromatolites include some of the most ancient records of life on Earth, and are still forming today. Within the human body, biofilms are present on the teeth as dental plaque , where they may cause tooth decay and gum disease.
These biofilms can either be in an uncalcified state that can be removed by dental instruments, or a calcified state which is more difficult to remove.
Removal techniques can also include antimicrobials. Dental plaque is an oral biofilm that adheres to the teeth and consists of many species of both bacteria and fungi such as Streptococcus mutans and Candida albicans , embedded in salivary polymers and microbial extracellular products. The accumulation of microorganisms subjects the teeth and gingival tissues to high concentrations of bacterial metabolites which results in dental disease.
The dental plaque biofilm can result in the disease dental caries if it is allowed to develop over time. An ecologic shift away from balanced populations within the dental biofilm is driven by certain cariogenic microbiological populations beginning to dominate when the environment favours them. The shift to an acidogenic , aciduric, and cariogenic microbiological population develops and is maintained by frequent consumption of fermentable dietary carbohydrate.
The resulting activity shift in the biofilm and resulting acid production within the biofilm, at the tooth surface is associated with an imbalance between demineralization and remineralisation leading to net mineral loss within dental hard tissues enamel and then dentin , the sign and symptom being a carious lesion. By preventing the dental plaque biofilm from maturing or by returning it back to a non-cariogenic state, dental caries can be prevented and arrested.
A peptide pheromone quorum sensing signaling system in S. This system is optimally expressed when S. Biofilm grown S. When the biofilm, containing S. Predator - prey interactions between biofilms and bacterivores, such as the soil-dwelling nematode Caenorhabditis elegans , had been extensively studied. Via the production of sticky matrix and formation of aggregates, Yersinia pestis biofilms can prevent feeding by obstructing the mouth of C.
Many different bacteria form biofilms, including gram-positive e. Bacillus spp, Listeria monocytogenes , Staphylococcus spp, and lactic acid bacteria , including Lactobacillus plantarum and Lactococcus lactis and gram-negative species e. Escherichia coli , or Pseudomonas aeruginosa.
Beyond Risk: Bacterial Biofilms and Their Regulating Approaches
Biofilm formation occurs when free floating microorganisms attach themselves to a surface. Although there are some beneficial uses of biofilms , they are generally considered undesirable, and means of biofilm prevention have been developed. Biofilms secrete extracellular polymeric substance that provides a structural matrix and facilitates adhesion for the microorganisms ; the means of prevention have thus concentrated largely on two areas: killing the microbes that form the film, or preventing the adhesion of the microbes to a surface. Because biofilms protect the bacteria, they are often more resistant to traditional antimicrobial treatments, making them a serious health risk. Chemical modifications are the main strategy for biofilm prevention on indwelling medical devices.
Bacterial infection of implants and prosthetic devices is one of the most common causes of implant failure. The nanostructured surface of biocompatible materials strongly influences the adhesion and proliferation of mammalian cells on solid substrates. The observation of this phenomenon has led to an increased effort to develop new strategies to prevent bacterial adhesion and biofilm formation, primarily through nanoengineering the topology of the materials used in implantable devices. While several studies have demonstrated the influence of nanoscale surface morphology on prokaryotic cell attachment, none have provided a quantitative understanding of this phenomenon. Using supersonic cluster beam deposition, we produced nanostructured titania thin films with controlled and reproducible nanoscale morphology respectively. We characterized the surface morphology; composition and wettability by means of atomic force microscopy, X-ray photoemission spectroscopy and contact angle measurements.
Electrical methods of controlling bacterial adhesion and biofilm on device surfaces. January ; Expert Review of Medical Devices 10(1)
Electrical methods of controlling bacterial adhesion and biofilm on device surfaces.
Skip to search form Skip to main content You are currently offline. Some features of the site may not work correctly. DOI: Freebairn and D. Linton and E. Harkin-Jones and D.
Note 1: A biofilm is a system that can be adapted internally to environmental conditions by its inhabitants. A biofilm comprises any syntrophic consortium of microorganisms in which cells stick to each other and often also to a surface. Biofilms may form on living or non-living surfaces and can be prevalent in natural, industrial, and hospital settings.
Секундой позже произошло столкновение, и Стратмор, сбитый с ног, кубарем покатился по кафельному полу шифровалки. Это был Хейл, примчавшийся на звук пейджера. Сьюзан услышала стук беретты, выпавшей из руки Стратмора.
Больше ждать он не мог: глаза горели огнем, нужно было промыть их водой. Стратмор подождет минуту-другую. Полуслепой, он направился в туалетную комнату.