Biofilms consist of a layer of mucus (a film) in which single or mixed populations of microorganisms (e.g. bacteria , algae , fungi , protozoa ) in concentrations of 10 12 cells per milliliter of biofilm and of multicellular organisms such as rotifers , roundworms , and mites , Little bristles or insect larvae that feed on the microorganisms are embedded. In everyday life, they are often perceived as a slippery, soft-feeling, water-containing slime layer or coating. Other colloquial terms are Aufwuchs , Kahmhaut or Sielhaut .
Biofilms are mainly formed in aqueous systems when microorganisms settle there at interfaces . In principle, all areas can be covered with biofilms: between gas and liquid phases (e.g. free water level), liquid and solid phases (e.g. gravel on the river bed) or between different liquid phases (e.g. oil droplets in the water ). The interface on which the biofilm forms, or more precisely the phase into which the film does not or hardly grows, forms the substratum ( substrate ; the one below).
In a broader sense, all aggregates of microorganisms that are embedded in a layer of mucus that they form are referred to as biofilms. Suspended solids in water often consist of mineral particles overgrown by biofilms. The activated sludge in sewage treatment plants also has essential properties of a biofilm. It consists of flakes that themselves have a surface suitable for colonization.
Biofilms can be regarded as a very primal form of life , because the oldest fossils that have been found so far come from microorganisms in biofilms that lived 3.2 billion years ago. These are stromatolites (biogenic sedimentary rocks) found in Western Australia ( Pilbara Kraton ). The biofilm as a form of life has proven itself so well that it is still widespread today. The vast majority of microorganisms live in nature in the form of biofilms.
Besides the microorganisms, the biofilm mainly contains water. Extracellular polymeric substances (EPS) secreted by the microorganisms form hydrogels in combination with water , creating a slimy matrix in which nutrients and other substances are dissolved. Inorganic particles or gas bubbles are also often enclosed by the matrix. The gas phase can be enriched with nitrogen , carbon dioxide , methane or hydrogen sulfide , depending on the type of microorganisms .
The EPS consist of biopolymers that are able to form hydrogels and thus give the biofilm a stable shape. This involves a wide range of polysaccharides , proteins , lipids and nucleic acids (extracellular DNA ).
Different types of microorganisms usually live together in biofilms. In addition to the original biofilm formers, other unicellular organisms ( amoeba , flagellates, etc.) can also be integrated. Aerobic and anaerobic zones can occur at a distance of a few hundred micrometers , so that aerobic and anaerobic microorganisms can live close together.
In the core area, the biofilm is usually compact (basic biofilm). The edge area (surface biofilm) can either also be compact and regularly shaped and form a flat boundary surface to the overflowing fluid or be blurred and much looser. In the latter case, the surface biofilm can resemble a mountain-and-valley path if, for example, bacterial species grow thread-like (filamentous) into the fluid or if the substratum is populated with protozoa (e.g. bell-shaped bells) or higher organism species.
The biofilm matrix is then often criss-crossed by pores, caverns and passages that enable the exchange of substances between the bacterial cells and a supply of water. Mushroom-shaped or tower-like structures are often found. There convective material transport processes occur when these are flowed through by liquid. In the area of the surface of the biofilm, convective mixing processes can also be triggered by the movement of outgrowths protruding into the flow (e.g. " sewage fungi " such as Sphaerotilus natans ). In the interior of biofilms, dissolved substances are mainly transported by diffusion . At the interface with the water, cells or entire parts of the biofilm can repeatedly be released and taken up by the water flowing past.
Formation and maturation of biofilms
The formation and formation of a biofilm can be divided into three phases: the induction phase (Figs. 4 and 6, 1–2) the accumulation phase (3) and the existence phase (4–5).
Colonization of surfaces
According to popular belief, typical microorganisms have flagella (Fig. 6, 1) and move freely in the water column. In fact, such swarming cells are usually only at the stage of spread of biofilm residents.
There is a compelling reason that the absolute majority of bacteria and archaea are rooted in biofilms: otherwise they would be washed out of their biotope by the water they need for life . Soil bacteria would end up in the next river and from there begin their last journey into the sediment of an ocean. The same thing happened to the microorganisms in the activated sludge of sewage treatment plants .
In order to be able to leave the free water at all, microorganisms need water-repellent hydrophobic substances on the surface of their cells. These enable the organisms to attach themselves to hydrophobic surfaces based on Van der Waals forces . Since almost all areas in aquatic biotopes are overgrown with biofilms, most swarming cells associate with existing biofilms.
Such organisms can also attach themselves directly to unpopulated areas. Smooth hydrophobic surfaces, such as B. Polystyrene or the cuticle of many plants can be colonized directly, but only if they can be wetted with water . However, thanks to the lotus effect , many plants avoid microorganisms from growing on their leaves.
A thin, viscous layer of organic substances is initially deposited on empty hydrophilic surfaces. These biopolymers come from the mucous membranes that form around bacterial cells (EPS), occasionally detach completely or partially and are adsorptively bound when they come into contact with interfaces . Such biogenic substances are ubiquitous in nature.
The metamorphosis to the biofilm inhabitant
When the place of attachment allows the organism to grow, it usually sheds its flagellum (s). In many organisms, however, a much deeper change occurs.
This is clearly visible in Caulobacter , an aerobic α-Proteobacterium . After losing the flagellum, the swarming cell retracts its pili, which are used for attachment, and becomes the pedicel cell. In contrast to the swarm cell, it is capable of dividing and begins immediately with an asymmetrical division. A new swarming cell arises. After the separation, the stem cell can repeatedly form new swarming cells under suitable conditions.
The changes in the soil bacterium Bacillus subtilis are at least as far-reaching (Fig. 6). Once the flagella has been attached and lost, the subsequent cell divisions result in filamentous structures because the cell walls of the organisms are not separated. At the same time, polymers are excreted, which give the resulting film lateral strength. Such changes are triggered epigenetically .
As a result of the multiplication of cells that have attached to a surface, the organisms spread. The interface is first populated over a large area in the form of a film (biofilm). At the same time or later, the biofilms grow in multiple layers and ultimately form heterogeneous three-dimensional structures. Up to this phase, Bacillus subtilis almost exclusively produces filamentous cell aggregates.
Avoidance of competition
In principle, there is competition between the cells of a biofilm for nutrients, in which those cells that are closest to the food source have a clear advantage. On the other hand, the cells inside threaten to starve to death. If that happens, then they are no longer able to maintain cohesion. In fact, there are mechanisms of cell density regulation and communication between cells ( quorum sensing ) that counteract this.
Such a mechanism was first elucidated in detail for Bacillus subtilis in 2015. For this purpose, a biofilm from a pure culture of these bacteria was examined in a chemostat bioreactor . The biofilm was continuously supplied with nutrients, and yet the cells stopped growing periodically until the cells inside the biofilm ceased to starve. This "oscillation" is based on the following sequence:
- Starving cells in the biofilm inside send a pulse of K + - ions from. The biofilm cells of B. subtilis have receptors for these ions that trigger a whole chain of events.
- All cells, including the well-supplied cells, send out a K + signal immediately upon receipt . Specific K + channels exist in the biofilm for the propagation of the signals . (Normal diffusion through the polymeric biofilm matrix would be too slow.)
- The cells that are still well supplied immediately interrupt their growth, but not their metabolic activity. If there is a lack of nitrogen, take B. glutamine from the nutrient medium, but do not use this amino acid for growth, but split off ammonium from it, which they make available to the biofilm.
- If the signals subside, growth will continue together.
Communication between K + -based bacterial cells is not the only one. There are a number of pheromones that can be formed and perceived by organisms. This also initiates the next phase in the existence of a biofilm (see Fig. 6.5). Again there is a metamorphosis of cells. In well-supplied swarm cells, flagellated swarm cells are formed whose preferred swimming direction is to the source of nutrients. Many bacteria, like B. subtilis, also form spores during this phase . These are carried along by the current and are prepared for long-term nutrient deficiencies.
This phase of emigration is by no means the end of a biofilm. For the release of the spores and swarming cells, the extracellular matrix is only actively dissolved in their surroundings . In the old part of the biofilm, life goes on with a new phase of growth.
The fact that the depth of the biofilm is limited can be seen when entire parts of the biofilm are carried away by the current. The cohesion of parts of the biofilm is lost through the formation of gas bubbles (e.g. through denitrification and carbon dioxide). The increase in the flow resistance with increasing thickness leads to increased erosion if the biofilm has formed on surfaces exposed to the flow. Life in such biofilm fragments is not fundamentally different from biofilms that are attached somewhere. Such flakes have all the properties for attachment to a new surface.
Life in the biofilm - protection and community
The life processes of the bacteria in the biofilm differ significantly from those in the planktonic state, i.e. in free suspension . The mobile swarming cells produce different EPS than in the biofilm state.
The matrix offers mechanical stability and allows the biofilm organisms to build up long-term synergistic interactions, to survive periods of starvation and prevents extracellular enzymes from being washed away .
Some genes are switched on and others switched off by surface contact. Using special signaling molecules , they can communicate with one another and switch other genes on and off. They expand their genetic repertoire through horizontal gene transfer by exchanging genes with neighboring cells.
This has resulted in a flexible, powerful and universal form of life that is definitely compared to multicellular organisms.
The biofilm offers the individual micro-organisms excellent protection and enables them to adapt to changing environmental conditions: This increases tolerance to extreme pH and temperature fluctuations, pollutants (e.g. bactericides ), but also UV and X-rays, as well as a lack of food .
Possible causes of this inhibition of harmful environmental influences are:
- Difficult penetration - the pollutants cannot penetrate the biofilms
- unfavorable conditions for the active substance in the biofilm
- high diversity of bacteria in the biofilm
- Different behavior of individual bacterial cells or groups at different points of the biofilm (in other words "closer" or "further away" from nutrients, oxygen ( aerobic and anaerobic areas), antibiotics or reactions of the immune system) - even with extensive bacterial death, isolated ones often survive this way so-called “persisters”, which, due to the nutrients present, have almost ideal conditions for renewed reproduction.
- slower growth rates of the bacteria in the biofilm - the bacteria sometimes show a reduced metabolism up to dormant stages (VBNC - “viable but not culturable”) and therefore absorb almost no antibiotic poisons; they essentially protect themselves by inactivity.
Biofilms occur everywhere - in all soils and sediments, on rock, on and in plants and animals, especially on the mucous membranes; in the ice of glaciers , in boiling springs , on rocks in the desert , in dilute sulfuric acid and dilute caustic soda , in pipes and tubes, in jet fuel and in oil tanks, in spaceships and submarines, even in highly radioactively contaminated areas of nuclear power plants. They form microbial mats in wetlands.
Biofilms are of great ecological importance. They are involved in the global cycles of carbon, oxygen, nitrogen, sulfur, phosphorus and many other elements. They mobilize substances from minerals. They bind a lot of carbon dioxide , thus counteracting the greenhouse effect .
The organisms within the biofilms are able to break down substances that are difficult to break down through their interaction. They play a central role in the self-cleaning processes of natural habitats. They play a key role in the self-cleaning of the water.
At interfaces or body cavities of animals there are "local" often non-pathogenic ( non-pathogenic ) biofilm populations. Examples of this are the bacterial communities of the skin, mouth and intestines ( skin , mouth and intestinal flora ). Plaque, the dental plaque that forms on teeth, also represents a biofilm. The bacteria involved enter into an interspecific interaction with the host . They are considered commensals as soon as they benefit from the host. If both types benefit, it is mutualism . In this form of interaction, the bacteria perform a number of tasks. They are important in the maturation of the immune system in the first few years of life. In addition, potentially pathogenic bacteria are kept away or the digestive processes are supported. If there is an imbalance in the population, this can lead to disease.
Although biofilms are ubiquitous in nature, their clinical importance in medicine is often underestimated. This applies in particular to infections, because in more than 60% of all bacterial infectious diseases, the pathogens protect themselves from the immune system by forming biofilms . Since a large part of the initial microbiological instruments was developed in the course of major epidemics , this was done with an emphasis on the free-floating (planktonic), rapidly dividing bacteria of acute infections (see Henle-Koch postulates ). The isolation and pure culture in the laboratory required here , however, leads to considerable loss of genes in the bacteria under conventional laboratory conditions and ultimately to the loss of the ability to form biofilms. Because of this, and because of the above- mentioned resting phases, biofilms in the accumulation phase often evade detailed examination in addition to detection by conventional methods of microorganism culture. Modern visualization techniques such as confocal microscopy and gene probes for localizing and identifying biofilm organisms using fluorescence microscopy have contributed to a better understanding of biofilms.
In the course of biofilm maturation, in the phase of existence, coordinated by quorum sensing , larger bacterial accumulations are shed. This creates a source of germs that lead to chronic and recurring infections in patients ( bacteremia ) and, under certain circumstances, even to the often fatal sepsis . This is especially true for patients with weakened immune systems. Biofilms have been linked to a number of infections. Examples for this are:
- chronic Lyme borreliosis , with or without nerve involvement ( neuroborreliosis or Lyme neuroborreliosis )
- Wound infections
- bacterial endocarditis
- Periodontal disease
- Dental caries
- chronic otitis media in children
Foreign body-associated infections are another area affected. This includes microbial contamination and colonization of catheters , implants and medical instruments. The increasing use of plastics in medical technology has, in addition to the great inherent advantages for diagnosis and therapy, exacerbated the biofilm problem. Because of the affinity of various microorganisms, such as some staphylococci , to the surfaces of biomaterials , around half of nosocomial infections can be traced back to surgical implants. The starting point for the microorganisms involved are the skin surface of hospital staff and patients, the contact of exit points or connectors with tap water and other sources in the environment. It can also affect the water lines of hospitals and dental treatment centers, as well as dialysis equipment and difficult-to-clean endoscopes. Depending on the medical device used and the length of stay, gram-positive, gram-negative bacteria and fungi occur as single or multi-species biofilms. Examples of frequently involved pathogens are:
- Borrelia burgdorferi , other species of Borrelia pathogenic to humans ( B. garinii, B. afzelii, B. valaisiana, B. lusitaniae and B. spielmanii )
- Staphylococcus epidermidis
- Staphylococcus aureus
- Pseudomonas aeruginosa
- Escherichia coli
- Candida albicans
Due to the partially unexplained increased general and antibiotic resistance of the bacteria in the biofilm (including through increased horizontal gene transfer, formation of "persisters" and high diversity - see above ), the removal of the respective implant is necessary in many cases . Systems with large surfaces and with skin penetration points are particularly at risk. Examples of medical devices frequently affected by foreign body-associated infections are:
- Venous catheter
- artificial heart valves
- Joint prostheses
- Peritoneal dialysis catheter
- Endotracheal tube
- Voice prostheses
- Cerebrospinal fluid shunts
- Dental implants
According to JW Costerton (see literature ), the use of processes and approaches from microbial ecology is expected to result in considerable synergies and thus a significant advance in the understanding and therapy of medically relevant biofilms for medical microbiology .
Biofilms can be detected on 60-90% of chronic wounds . They play a key role in the development of normal tissue damage into a chronic wound. A biofilm that covers the wound base disrupts the healing process and also endangers those affected, whose immune status is restricted by the chronic wound or the underlying disease. The removal of the biofilm is therefore a fundamental part of wound care. To remove the Biofims measures are of debridement is used, for example, therapeutic larvae or ultrasound -assisted wound cleansing. The subsequent local antiseptic treatment of the wound prevents the reconstruction of the biofilm on the wound bed.
In order to prevent the contamination of water and food , but also of medicines and cosmetics by microorganisms, constant measures against biofilm formation are necessary. Every year, large amounts of water contaminated by cleaning agents and disinfectants are produced .
Biocorrosion is observed in the presence of biofilms. Iron oxidizers contained in the oxygen-loving (aerobic) top layer lead to an attack on the passive layer (of metals) - sulphate reducers in the anaerobic layer attach to these points and “eat” their way into the material.
Microbiologically induced corrosion causes considerable economic damage every year. The proportion of total corrosion (i.e., abiotic and biotic corrosion) is estimated to be at least 20%; according to more recent findings, it is probably significantly higher. Even higher-alloy materials such as V2A and V4A will be damaged. Almost all technical systems are affected: u. a. Cooling circuits, water treatment and service water systems, energy generation in power plants, the production of cars, computers, paints, the oil and gas industry. In old mining sites, biological leaching of minerals by biofilms leads to extensive environmental damage in soil, water and air through dust pollution and emissions of sulfuric acid, heavy metals, radon and radionuclides.
In the case of water treatment using membrane processes, biofilms are responsible for the biofouling , which leads to serious disturbances with this technology.
Biofouling also includes biofilms that form on underwater bodies. This can lead to significant problems. A biofilm of only a tenth of a millimeter reduces the speed of a tanker by 10 to 15 percent due to increased frictional resistance . This results in increased fuel consumption. In the fight against organic growth (including barnacles and mussels), special substances are painted on ships, platforms and buoys, the active ingredients of which are released into the water and often pose a significant environmental impact. One such substance is the highly toxic tributyltin (TBT) , which has now been banned worldwide . Also affected are sensor systems for research or monitoring purposes in the maritime sector, where vegetation can very quickly lead to functional impairments.
Concentration gradients of physico-chemical parameters in biofilms can be determined using high-resolution microsensors (= functional examination) and correlated with molecular biological data from the depth distribution of the microbial populations present in the biofilm (= structural examination). The ideal goal is to combine the structure and function of the microbial populations in the biofilm with (damage / corrosion) data from the growth area. This contributes to a better understanding of the interaction between the damage-causing biofilm and the growth area, which is of particular interest in applied systems (e.g. marine biofilms in steel pipes).
Biofilms in evaporative cooling systems
In evaporative cooling systems, biofilms can damage the health of employees. Pseudomonas aeruginosa is one of the first colonizers of biofilms and can cause inflammatory diseases. Direct contact with skin and airways can occur, particularly during cleaning and maintenance work.
Biotechnology is already making interfaces usable in many ways. This ranges from the use of immobilized, i. H. surface-bound enzymes and microorganisms via wastewater treatment with biofilm reactors and biological waste treatment to microbial leaching of ores.
One of the best known examples of the industrial use of biofilms is probably the production of vinegar with the help of vinegar bacteria , which, either as a scum on a liquid containing alcohol (Orléans process) or settled on wood chips (generator process), form a biofilm that converts ethanol into acetic acid.
Use in wastewater technology
The use of immobilized microorganisms for wastewater treatment in the form of biofilms began as early as the 19th century. Biofilm processes are very suitable for wastewater treatment. The microorganisms are bound to a solid surface and are therefore not discharged from the sewage treatment plant with the wastewater.
The substances that pollute the water are a source of energy and food for microorganisms. Biofilms with their branched structure have a very large adsorption surface. As a result, substances that cannot be processed immediately can, to a certain extent, be attached to the biofilm and then broken down in periods with little food intake.
Biological waste disposal
Biofilms make biological waste disposal possible by colonizing and breaking down the waste.
Biological exhaust gas cleaning
With exhaust gas cleaning by means of a bioresel bed reactor , a biofilm is used to break down the air pollutants that have passed into the aqueous phase.
Even soil pollutants such as spilled oil can be broken down by the relevant microorganisms.
Prevention / control of biofilms
Several independent institutes confirm that in the sustainable elimination of biofilms in technical systems, water disinfection with full metal catalysts in connection with low use of hydrogen peroxide has been successful in technical use for more than ten years (first technical use 1997). Through the biochemical utilization of germs, biosurfactants are formed on the catalyst , which eliminate the species-specific biofilm.
Other institutes, however, state that the sole use of hydrogen peroxide has no effectiveness in terms of disinfection. An H 2 O 2 concentration of 150 mg / L with a contact time of 24 hours showed neither a killing nor a detaching effect when disinfecting drinking water systems, not even through the addition of silver ions (150 µg / L). Since the biocide treatments did not remove biofilms, but rather the dead biomass remained on the surfaces, a selection of resistant individual organisms (“persisters”) and the introduction of new organisms into the test system quickly lead to re-germination.
The disinfectant chlorine dioxide shows good biofilm degradation. The molecule is electrically neutral and can penetrate the EPS layer of biofilms and the cell membranes of microorganisms. In contrast, elemental chlorine, which disproportionates to hydrochloric acid and hypochlorous acid in water, proves to be significantly less effective, because depending on the pH value it is partially present as a hypochlorite ion and this - due to its negative charge - a biofilm and Cell membrane penetration no longer reliably guaranteed.
In addition, the process of light-induced catalysis for water treatment has been around for a few years . Based on natural processes from nature, water-bearing systems are kept in a biofilm-free state in the presence of a suitable catalyst under the influence of daylight.
There are also various, mostly experimental, methods to prevent or combat biofilms. In this context, prevention is often used to prevent biofilms from forming in the first place. Examples of different approaches are:
- Minimize the entry of organic nutrients in order to deprive the microorganisms of their livelihood
- Measures to disinfect and sterilize the water, e.g. B. Chlorination
- mechanical destruction of biofilms
- In biotechnology, biofilms must be prevented in pipelines that transport pure and ultrapure water. As a rule, ozone is fed in for this purpose .
- antimicrobial peptides (AMPs)
- Disturbance of communication ( quorum sensing ) of the bacteria in the biofilm to prevent settlement or detachment
- with enzymes
- with so-called furanones (the Australian red alga Delisea pulchra is used as a model )
- Surface modification (bacteria-repellent coatings)
- Nanostructuring (see lotus effect )
- negative charge
- Plasma treatment, e.g. B. applying diamond-like carbon (diamond-like carbon (DLC))
- Avoidance of rough surfaces
- antibiotic coating, e.g. B. Minocycline - rifampicin
- antiseptic coating, e.g. B. Chlorhexidine - silver sulfadiazine
- Introduction of metals, e.g. B. silver, platinum, bismuth
- Bacterial coating, e.g. B. non-pathogenic (non-pathogenic) Escherichia coli on urinary catheter
- dynamic surfaces (often with a bionic approach)
- electrical current
- "Skinning" or "Peeling"
- “Growing out” of structures
- "Slime formation"
- Vibration of the surface
- Hans-Curt Flemming: Biofilms - Life on the Edge of the Water Phase . In: News from chemistry . 4 (2000), pp. 442-447.
- Hans-Curt Flemming, Jost Wingender: Biofilms - the preferred form of life for bacteria: flakes, films and sludge . In: Biology in Our Time . 31 (3) (2001), , pp. 169-180.
- John William "Bill" Costerton: The Biofilm Primer (Springer Series on Biofilms) . Springer-Verlag, Berlin / Heidelberg / New York 2007, ISBN 978-3-540-68021-5 , doi: 10.1007 / b136878 .
- R. Walter, K. Büsching, H. Lausch: Water disinfection with full metal catalysts and hydrogen peroxide. In: water, soil, air. 1-2 / 2005, p. 30.
- Flemming, H.-C., Wingender, J. (2010): The Biofilm Matrix. Nat. Rev. Microbiol. 8 623-633
- A. Houry, M. Gohar et al. a .: Bacterial swimmers that infiltrate and take over the biofilm matrix. In: Proceedings of the National Academy of Sciences of the United States of America . [Electronic publication before printing] July 2012. doi: 10.1073 / pnas.1200791109 , PMID 22773813 .
- Garth D. Ehrlich, Patrick J. DeMeo, J. William Costerton, Heinz Winkler (Eds.): Culture Negative Orthopedic Biofilm Infections , Series: Springer Series on Biofilms, Vol. 7, 2012, ISBN 978-3-642-29553- 9 (Print) 978-3-642-29554-6 (Online)
- Flemming, H.-C., Wingender, J., Kjelleberg, S., Steinberg, P., Rice, S., Szewzyk, U. (2016): Biofilms: an emergent form of microbial life. Nat. Rev. Microbiol. 14, 563-575
- Biofilm Center (University of Duisburg-Essen): Why biofilm research?
- Stern.de - Science and Health, November 27, 2006: Biofilms: Bacteria-WG in the pacemaker
- Michael Lange and Martin Winkelheide : A universe made of slime - How bacteria live in biofilm , Deutschlandfunk - Science in focus from June 11, 2006:
- Institute for Environmental Process Engineering at the University of Bremen - Abwasserlexikon: Biofilm
- Press release: DFG research group "Physical Chemistry of Biofilms"
- Society of German Chemists (GDCh): Biofilms in water - useful or harmful? ( Memento from March 5, 2008 in the Internet Archive )
- Center for Biofilm Engineering: What is biofilm? ( Memento of May 3, 2010 on the Internet Archive ), Montana State University
- Biofilms: The Hypertextbook , January 4, 2010 version, Montana State University
- Karl Höll: Water. ISBN 978-3-110-22677-5 , p. 669 ( limited preview in Google book search).
- Michel Vert, Yoshiharu Doi, Karl-Heinz Hellwich, Michael Hess, Philip Hodge, Przemyslaw Kubisa, Marguerite Rinaudo, François Schué: Terminology for biorelated polymers and applications (IUPAC Recommendations 2012) . In: Pure and Applied Chemistry . 84, No. 2, 2012, pp. 377-410. doi : 10.1351 / PAC-REC-10-12-04 .
- Andreas Schmidt-Wilckerling: Metabolic activity of freely suspended and immobilized cells of ammonia-oxidizing bacteria. Diploma thesis, Hamburg (1989).
- Luanne Hall-Stoodley, J. William Costerton a. a .: Bacterial biofilms: from the natural environment to infectious diseases . In: Nature Reviews Microbiology . Vol. 2, No. 2, 2004, , PMID 15040259 , doi: 10.1038 / nrmicro821 , pp. 95-108 (PDF file; 0.6 MB) .
- Hera Vlamakis, Yunrong Chai, Pascale Beauregard, Richard Losick, Roberto Kolter: Sticking together: building a biofilm the Bacillus subtilis way . In: Nat Rev Micro . 11, No. 3, 2013, pp. 157-168. doi : 10.1038 / nrmicro2960 .
- Yunrong Chai, Thomas Norman, Roberto Kolter, Richard Losick: An epigenetic switch governing daughter cell separation in Bacillus subtilis . In: Genes & Development . 24, No. 8, 2010, pp. 754-765. doi : 10.1101 / gad.1915010 .
- Jintao Liu, Arthur Prindle, Jacqueline Humphries, Marcal Gabalda-Sagarra, Munehiro Asally, Dong-yeon D. Lee, San Ly, Jordi Garcia-Ojalvo, Gurol M. Suel: Metabolic co-dependence gives rise to collective oscillations within biofilms . In: Nature . 523, No. 7562, 2015, pp. 550-554. doi : 10.1038 / nature14660 .
- Arthur Prindle, Jintao Liu, Munehiro Asally, San Ly, Jordi Garcia-Ojalvo, Gurol M. Suel: Ion channels enable electrical communication in bacterial communities . In: Nature . 527, No. 7576, 2015, pp. 59-63. doi : 10.1038 / nature15709 .
- James A Shapiro: Thinking about bacterial populations as multicellular organisms . In: Annual Reviews in Microbiology . 51, No. 1, 1998, pp. 81-104. doi : 10.1146 / annurev.micro.52.1.81 .
- Carl R. Woese, Nicholas Chia, Nigel Goldenfeld: A collective mechanism for phase variation in biofilms . In: Proceedings of the National Academy of Sciences . 105, No. 38, 2008, pp. 14597-14602. doi : 10.1073 / pnas.0804962105 .
- Kim Lewis: Riddle of biofilm resistance . In: Antimicrobial agents and chemotherapy . Vol. 45, No. 4, 2001, , PMID 11257008 , doi: 10.1128 / AAC.45.4.999-1007.2001 , pp. 999-1007 (PDF file; 0.2 MB) .
- Ulrich Szewzyk, Regine Szewzyk: Biofilms - the slightly different way of life . In: BIOspectrum . Vol. 9, 2003, , pp. 253-255. (PDF file; 0.3 MB).
- C. Mark Ott, Rebekah J. Bruce et al. a .: Microbial characterization of free floating condensate aboard the Mir space station . In: Microbial ecology . Vol. 47, No. 2, 2004, PMID 14569419 , doi: 10.1007 / s00248-003-1038-3 , pp. 133-136, PDF file; 0.9 MB. ( Memento from May 15, 2009 in the Internet Archive ) ,
- Joe J. Harrison, Raymond J. Turner, et al. a .: Biofilms - A new understanding of these microbial communities is driving a revolution that may transform the science of microbiology . In: American scientist . Vol. 93, No. 6, 2005, doi: 10.1511 / 2005.6.508 , pp. 508-515. (online version) ( Memento of the original from November 17, 2007 in the Internet Archive ) Info: The archive link was inserted automatically and has not yet been checked. Please check the original and archive link according to the instructions and then remove this notice. . ,
- Christoph A. Fux, J. William Costerton a. a .: Survival strategies of infectious biofilms . In: Trends in microbiology . Vol. 13, No. 1, 2005, PMID 15639630 , doi: 10.1016 / j.tim.2004.11.010 , pp. 34-40. ,
- Yogita N. Sardessai: Viable but non-culturable bacteria: their impact on public health . In: Current science . Vol. 89, No. 10, 2005, (PDF file; 0.01 MB) . , p. 1650.
- Eliana Drenkard, Frederick M. Ausubel: Pseudomonas biofilm formation and antibiotic resistance are linked to phenotypic variation . In: Nature . Vol. 416, No. 6882, 2002, , PMID 11961556 , doi: 10.1038 / 416740a , pp. 740-743 (PDF file; 0.3 MB)
- J. William Costerton, Philip S. Stewart u. a .: Bacterial biofilms: a common cause of persistent infections . In: Science . Vol. 284, No. 5418, 1999, , PMID 10334980 , pp. 1318-1322.
- Luanne Hall-Stoodley, Fen Ze Hu et al. a .: Direct detection of bacterial biofilms on the middle-ear mucosa of children with chronic otitis media . In: The Journal of the American Medical Association . Vol. 296, No. 2, 2006, , PMID 16835426 , doi: 10.1001 / jama.296.2.202 , pp. 202-211.
- Joseph M. Patti: Vaccines and immunotherapy for staphylococcal infections . In: The international journal of artificial organs . Vol. 28, No. 11, 2005, PMID 16353122 , pp. 1157-1162. ,
- Rodney M. Donlan: Biofilms and device-associated infections . In: Emerging Infectious Diseases . Vol. 7, No. 2, 2001, , PMID 11294723 , pp. 277-281. (PDF file; 0.1 MB) .
- Henk J. Busscher, Gésinda I. Geertsema-Doornbusch u. a .: Adhesion to silicone rubber of yeasts and bacteria isolated from voice prostheses: influence of salivary conditioning films . In: Journal of biomedical materials research . Vol. 34, No. 2, 1997, PMID 9029300 , doi : 10.1002 / (SICI) 1097-4636 (199702) 34: 2% 3C201 :: AID-JBM9% 3E3.0.CO; 2- U , pp. 201-209. ,
- Klaus Müller: Leave everything to the patient? . In: Dental Magazin 5/2007, pp. 36-39 http://www.zahnheilkunde.de/beitragpdf/pdf_5318.pdf . ,
- D. Keast, T. Swanson, E. Carville, I. Fletcher, G. Schultz, J. Black: Ten Top Tips. Understanding and managing wound biofilm in Wounds International Journal 2014, 5 (2), pages 20-24
- Christine Murphy, Lianne Atkin, Terry Swanson et al: Defying hard-to-heal wounds with an early antibiofilm intervention strategy: wound hygiene. An international consensus document , Journal of Wound Care, Vol 29, March 2020 Text online at MAG online library accessed on July 19, 2020
- Kerstin Protz: Modern wound care practical knowledge, standards and documentation , Elsevier Verlag Urban & Fischer, Munich 2016, ISBN 978-3-437-27885-3 , pages 27-28
- C. U. Schwermer, G. Lavik, RMM Abed, B. Dunsmore, TG Ferdelman, P. Stoodley, A. Gieseke, D. de Beer: Impact of nitrate on the structure and function of bacterial biofilm communities in pipelines used for injection of seawater into oil fields. In: Applied and Environmental Microbiology. 74 (2008), pp. 2841-2851. (online) .
- VDI 2047 sheet 2: 2015-01 recooling plants; Ensuring the hygienic operation of evaporative cooling systems (VDI cooling tower rules) (Open recooler systems; Securing hygienically sound operation of evaporative cooling systems (VDI Cooling Tower Code of Practice)). Beuth Verlag, Berlin. P. 11.
- VDI 3478 sheet 2: 2008-04 Biological exhaust gas cleaning; Bioriesel bed reactors (Biological waste gas purification; Biological trickle bed reactors). Beuth Verlag, Berlin. P. 12.
- Jürgen Koppe, Stefan Winkens: Full compliance with VDI 6022 - made possible by solid-state catalysts in the H 2 O 2 disinfection of air humidifiers . In: HLH ventilation / air conditioning, heating / sanitation, building technology . Vol. 59, No. 2, 2008, , pp. 22-27.
- Information Center for Corporate Environmental Protection (IBU) ( Memento of the original from January 16, 2017 in the Internet Archive ) Info: The archive link was automatically inserted and not yet checked. Please check the original and archive link according to the instructions and then remove this notice.
- Simone Schulte: Effectiveness of hydrogen peroxide against biofilms , dissertation at the University of Duisburg-Essen, 2003.
- Till Elgeti, Sebastian Janning, Jan Koppe, Jürgen Koppe: Light-induced catalysis in water treatment. In: WLB. 05/2010. (online) ( Page no longer available , search in web archives ) Info: The link was automatically marked as defective. Please check the link according to the instructions and then remove this notice. .
- Timothy K. Lu, James J. Collins: Dispersing biofilms with engineered enzymatic bacteriophage . In: Proceedings of the National Academy of Sciences of the USA . Vol. 104, No. 27, 2007, , PMID 17592147 , doi: 10.1073 / pnas.0704624104 , pp. 11197-11202. (PDF file; 1.7 MB) .
- Jemy A. Gutierrez, Tamara Crowder et al. a .: Transition state analogs of 5'-methylthioadenosine nucleosidase disrupt quorum sensing . In: Nature Chemical Biology . Published online, March 8, 2009, doi: 10.1038 / nchembio.153
- Barbara W. Trautner, Richard A. Hull u. a .: Coating urinary catheters with an avirulent strain of Escherichia coli as a means to establish asymptomatic colonization . In: Infection Control and Hospital Epidemiology . Vol. 28, No. 1, 2007, , PMID 17230395 , doi: 10.1086 / 510872 , pp. 92-94.
- Tzadik Hazan, Jona Zumeris u. a .: Effective prevention of microbial biofilm formation on medical devices by low-energy surface acoustic waves . In: Antimicrobial Agents and Chemotherapy . Vol. 50, No. 12, 2006, , PMID 16940055 , doi: 10.1128 / AAC.00418-06 , pp. 4144-4152.
(FSE) Georg Fuchs, Hans Günter Schlegel, Thomas Eitinger: General Microbiology . 9th, completely revised and expanded edition. Georg Thieme Verlag, Stuttgart 2014, ISBN 978-3-13-444609-8 .
- chap. 18. Bernhard Schink: The role of microorganisms in the material cycle and in nature . Pp. 598-635.
- chap. 16. Gottfried Linden: Regulation of metabolism and cell structure , here p. 522
- p. 527
- p. 609.
- p. 610.
- p. 527
- p. 527.
- pp. 521-523
- p. 527
- p. 522.