Microbial biofilms evoke Jackal & Hyde effects
microbes such as bacteria tend to live in complex colonies called biofilms, where there can resist antibiotics and cause more problems for the immune system. Biofilms comprising millions of bacteria are at the root of many serious chronic infectious diseases such as cystic fibrosis and periodontal disease, as well as industrial contamination, biofouling and biocorrosion.
Yet biofilms also have equal potential for good behaviour, in particular as agents of self-purification in streams and rivers, waste and pollution treatment, or generation of carbon-neutral electricity. These critical properties are derived from the existence of the protective slimy matrix within which members of the community live, preventing attack from both the immune system and antibiotics, but at the same time shielding them from toxic contaminants while breaking down waste or effluent.
The study of biofilms has emerged over the last three decades in various disciplines such as biotechnology, bioengineering or infectious disease research, leading to rapid progress, but also fragmentation and duplication of effort. The European Science Foundation (ESF) has stepped in to unite Europe's effort and bring together scientists with the required skills in relevant fields such as genetics, molecular biology, microscopy, medical microbiology, environmental science and ecology. The programme began with an Exploratory Workshop in September 2007, leading to a proposal for a new body to coordinate activities, the European Biofilm Net (EBN). The ESF workshop highlighted the huge potential and importance of biofilms, and also drew attention to exciting work unravelling the complex genetic and cellular interactions within these small yet teeming communities.
As the ESF Biofilm workshop's convenor Tom J. Battin, from the University of Vienna, pointed out, biofilms are involved in most chronic infections, including killers such as cystic fibrosis, and endocarditis in the heart. In cystic fibrosis, excess mucus production in the airways gives sanctuary to bacteria such as Pseudomonas aeruginosa, which actually mop up the dead carcasses of white blood cells sent by the immune system, enabling them to construct their protective biofilm coat. In this case the immune system is the architect of its own problems, helping create the shield used to repel its own agents, as well as resisting antibiotics. Indeed resistance against antibiotics is itself one of the biggest problems of all associated with biofilms, Battin noted.
"This becomes particularly dramatic for endocarditis patients, as was outlined at the workshop by Annette Moter from the Charite in Berlin," said Battin. Endocarditis is a rare but serious disease in which one of the four heart valves, the heart lining, or heart muscle, are infected by a bacterial biofilm, often comprising streptococci, and become inflamed. As the biofilms are resistant to antibiotics and the immune system's white blood cells, very often the only remedy is surgery, to replace a damaged valve, which can itself cause problems. The hope is that greater understanding will yield new drugs that reach the infected heart valve and break up the biofilm.
As Battin pointed out, biofilms can pose a big problem in large-scale water treatment plants, and yet for the very same reasons can play a positive role in the very same process, breaking down contaminants in waste and natural waters, for example. Further research will help ensure that the positive role is accentuated, while avoiding the problems.
The ESF workshop also highlighted greater understanding of the complex interactions within biofilms, which often comprise not just one species of bacteria, but a whole host of different micro-organisms, including archaea, protozoa, fungi, and even tiny metazoa actually comprising multiple cells. Many biofilms are in fact complete micro-ecosystems, within which there is competition as well as cooperation, and unraveling the interactions will reveal valuable insights into how these evolved.
Yet there is also great excitement about an emerging application that could have some potential for green energy production - the use of biofilms to power microbial fuel cells whose fuel could be wastewater, as outlined at the ESF workshop by Cristian Picioreanu, Delft University of Technology. This exploits the ability of bacteria to transfer electrons to metals, which can be the cathode of a fuel cell, via the minute tentacles called phili extending from their surface.
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