Biofilm Formation
A Brief history of “biofilm”
Center for Biofilm Engineering
Montana State University
Microbial communities attached to surfaces (biofilms) were observed long before people had the tools to study them in detail. In 1684 Antony van Leeuwenhoek remarked on the vast accumulation of microorganisms in dental plaque in a report to the Royal Society of London: “The number of these animalcules in the scurf of a man’s teeth are so many that I believe they exceed the number of men in a kingdom.”
The study of microbes took an important turn in the mid-1800s, when Robert Koch developed methods to create a solid nutrient medium in order to grow and isolate pure cultures of microorganisms. This development led to huge advances in medicine, agriculture, and industry. However, these advances were based on such a simplistic concept of microbial life that many ‘solutions’ generated by these techniques are now being reversed. Microorganisms have proved to be much more complex and less tractable than we ever imagined.
In a 1940 issue of the Journal of Bacteriology, authors H. Heukelekian and A. Heller wrote, “Surfaces enable bacteria to develop in substrates otherwise too dilute for growth. Development takes place either as bacterial slime or colonial growth attached to surfaces.” Claude ZoBell described many of the fundamental characteristics of attached microbial communities in the 1940s. In the late decades of the 20th century, numerous articles were written about microbial films or slime layers; German researchers sometimes used the term “Schmutzdecke.” As the unique properties of microbial communities vs planktonic microbes grew more apparent, it became helpful to use a special term to describe them. “Biofilm” was used colloquially among researchers for some years before it was considered a term acceptable for use in publication. The earliest use of “biofilm” in publication is in the Swedish journal Vatten: Harremoës, P. 1977. “Half-order reactions in biofilm and filter kinetics,” Vatten, 33 122-143. (If you know of an earlier publication with “biofilm” in it, please let us know; we would be happy to make a correction.)
Early biofilm researchers studied the implications of biofilms in waste-water filtration, biofouling of industrial equipment, and dental plaque (Leewenhoek would have been pleased). Since bacteria preferentially attach to surfaces, biofilms are virtually ubiquitous. Biofilm formation is also implicated in microbiologically influenced corrosion (MIC), product contamination, medical device-related infections, and chronic wounds. Biofilm can also be used for positive effects, especially in water pretreatment systems and contaminated soils.
In 1990, recognizing the significance of microbial activity, as well as the tremendous economic costs associated with microbial communities on surfaces, the US National Science Foundation founded the Center for Biofilm Engineering at Montana State University in Bozeman (though, interestingly, NSF would not initially accept the word “biofilm” in the Center’s name; instead the award funded the “Center for Interfacial Microbial Process Engineering”). Since that time, the field of biofilm research has exploded. New tools and techniques are continually pioneered to help understand the secrets of microbial community interactions. In addition to numerous research laboratories in the US, several groups study biofilms worldwide, including centers in Denmark, England, Germany, Australia, and Singapore.
What is a biofilm?
Most of you have never heard of the term “biofilm”, but you have certainly encountered “biofilm” on a routine basis. If you’ve ever been to the dentist and he’s scraped “plaque”, which causes tooth decay, off your teeth; that’s a type of bacterial biofilm. The “slim” that clogs your drains is also biofilm. The slippery coating on rocks, at the water’s edge of a stream or river, is just a bacterial biofilm-coating. Pond-scum – a biofilm. If you’ve ever been diagnosed with Candida albicans; H. pylori; chronic sinus or prostate infection; or Lyme disease, chances are they’re living, hiding and replicating in a biofilm colony.
Iodine staining of biofilm plaque (upper right)
This is the best product for removing the bacterial biofilm that causes plaque – Biotene PBF Chewing Gum.
These microorganisms (biofilm colonies) are usually encased in an extracellular polysaccharide (*) that they themselves synthesize, via the release of signaling molecules through quorum sensing (QS). This glue-like substance allows them to anchor to all kinds of surfaces – such as metals, plastics, soil particles, medical implant materials such as pacemakers, and tissue. As long as sufficient moisture and nutrients are available, a bacterial biofilm can form just about anywhere. In your body that would be from your mouth, especially the teeth, through the stomach and GI tract, all the way down to the rectum. Biofilm in the environment can be found, most often, in ponds, streams, rivers, etc. A biofilm can be formed by a single bacterial species, but more often than not, biofilms consist of many species of bacteria, as well as fungi/yeast, algae, protozoa, debris and corrosion products. Once anchored to a surface, biofilm microorganisms carry out a variety of detrimental or beneficial reactions, depending on the surrounding environmental or body conditions.
(*) Extracellular polymeric substances, or EPS, are the slimy material that bacteria excrete and surround themselves with as they form biofilms. EPS are mostly water (up to 95%), but the remaining ingredients include a complex mixture of lipids, saccharides (sugars), and bacterial debris such as cell fractions, DNA, and proteins.
In the human body, biofilm colonies are the main reason that certain conditions take so long to get handled. In my opinion, if it were not for “biofilm”, conditions caused by the microorganisms – Candida albicans, Candida spp, H. pylori, Lyme’s bacteria (Borrelia burgdorferi) and many others, would be far easier to diagnose and/or treat. It is crucial in any treatment protocol to first handle the biofilm. By doing so, it will make a significant difference in the amount of time, money and effort spent on treating many, so called, stubborn condition – like the above.
THE ROLE OF EXTRACELLULAR DNA IN MAINTENANCE OF BIOFILMS FORMED BY E. COLI, H. INFLUENZAE, K. PNEUMONIAE, P. AERUGINOSA, S. AUREUS, S. PYOGENES AND A. BAUMANNII George V. Tetz & Victor V. Tetz Dept. of Microbiology, Virology and Immunology; Saint-Petersburg State Pavlov Medical University, Russia Email: vtetzv@yahoo.com
It is known that bacteria within biofilms are much less susceptible to antibiotics particularly because of poor antimicrobial penetration through surface film that covers microbial community and inactivating role of extracellular matrix. Combined effects of DNase (Enzyme for digesting single and double-stranded DNA) and antibiotics on established biofilms of different unrelated bacteria were displayed. A Combination of antibiotics with DNase I resulted in significant decrease of established biofilm biomass compared to the reduction of biomass achieved when antibiotics or DNase I were used alone.
DETECTION OF HELICOBACTER PYLORI IN BIOFILMS BY USING REAL-TIME POLYMERASE CHAIN REACTION (PCR) Linke, S., Gebel, J., Büttgen, S., Exner, M. Institute for Hygiene and Public Health, University of Bonn
Our results confirmed a possible existence of H. pylori in drinking-water biofilms.
ANALYSIS AND IDENTIFICATION OF THE BIOFILM WOUND MICROFLORA IN HORSE WOUNDS Samantha J. Westgate1, Steven L Percival2*, Derek C. Knottenbelt1 and Christine A. Cochrane1 1University of Liverpool, Department of Veterinary Clinical Science, Division of Equine Studies, Leahurst, Neston, South Wirral, UK *2ConvaTec Wound Therapeutics, Deeside, Flintshire CH5 2NU, UK
Equine wound healing is notoriously problematic on the lower limb, specifically when biofilms are evident. Equine chronic wounds display similar characteristics to chronic wounds in humans thus these cases provide an effective model for human cases. Whether wounds are caused by trauma or surgery their high prevalence is of concern and treatment can be both challenging and costly. Biofilms are considered detrimental to normal healing in non-healing and infected chronic wounds because of their recalcitrant nature towards antimicrobial agents. Biofilms are also known to be resistant to the effects of the immune system. Because of this fact more research in the area of chronic wounds and biofilms is warranted.
Culturable analysis of the microflora revealed that the majority of bacteria isolated from the chronic wounds of horses were Staphylococcus spp, Pseudomonas spp, Micrococcus spp, Enterococcus spp, Corynebacterium spp, Streptococcus spp, Bacillus spp, Aerococcus spp and Clostridium spp. Further analysis of all isolates highlighted their biofilm forming potential and antibiotic resistance profiles. Biofilms were shown to be evident in a large percentage of the chronic wounds. In conclusion these studies provide evidence that biofilms exist in the chronic wounds of horse which may well provide an underlying reason as to why a large percentage of chronic wounds are recalcitrant to antimicrobial therapies, do not heal a timely manner and often become infected.
BACTERIAL BIOFILMS IN SURGICAL SPECIMENS OF PATIENTS WITH CHRONIC RHINOSINUSITIS (sinusitis).
Sanclement JA, Webster P, Thomas J, Ramadan HH. Department of Otolaryngology, West Virginia University, Morgantown, West Virginia 26506-9200, USA.
CONCLUSIONS: Biofilms were demonstrated to be present in 80% the 30 patients undergoing surgery for chronic rhinosinusitis (CRS); none of the (control) patients without CRS had any evidence of biofilms.
Note: According to Andrew Foreman, B.M.B.S., Ph.D., and colleagues from the University of Adelaide in Australia, the most common bacteria reeking havoc in those experiencing CRS is Staphylococcus aureus (S. aureus).
