However, the effectiveness of antibiotics is in decline and might soon disappear altogether. The reason is the development of antibiotic resistance in disease-causing bacteria. One hundred years after the discovery of penicillin in 1928, resistance to antibiotics will have reached levels never encountered before. Antibiotic resistance is a problem even now, and the most publicised example is MRSA. MRSA stands for methicillin-resistant Staphylococcus aureus and is a public health concern all over the world. In the UK alone, thousands of people die each year after MRSA infection, and over the last decade the number of cases - and newspaper articles - increased dramatically. The problem is that MRSA is very difficult to treat, not least because this particular type of Staphylococcus aureus bacteria is resistant to most antibiotics, including methicillin. And from everything we know, it is very likely that more and more disease-causing bacteria will become as resistant as MRSA over the next decades.
One obvious way to counter the threats of antibiotic resistance is the development of new antibiotics, but this has become increasingly difficult. Nevertheless, many disease-causing bacteria have a weak point besides antibiotics: they communicate.
When bacterial cell-to-cell communication was discovered it was a big surprise in itself, because scientists had previously assumed that cells communicate only in more complicated organisms like plants or animals. Cell-to-cell communication in bacteria only became common knowledge in 1994 when the term .quorum sensing. was coined by a group led by Pete Greenberg. Quorum sensing is a very simple system by which bacteria can detect their concentration in the environment. Every single bacterium in a population secretes a specific amount of a signalling molecule, which can be sensed by the other bacteria. The more bacteria there are around, the more of the signal molecule there will be. Each cell can in this way sense the molecule concentration and therefore the cell concentration. Based on this simple principle, bacterial populations can co-ordinate their behaviour. An example of such behaviour is the expression of virulence proteins by many disease-causing bacteria. Virulence proteins are molecules which enable bacteria to attack the infected organism. However, the infected organism might have immunological defences which 'kick in' when it senses the virulence proteins. This is bad news if there are only a few bacteria, as it will be easy for the immunological defences to eradicate them. However, bacteria can delay the production of the virulence proteins until their population has reached a specific concentration. They then start the production of virulence proteins in a co-ordinated manner, which increases their chances of surviving the immunological defences because there are more of them. The way in which the bacteria co-ordinate the start of production of virulence proteins is of course quorum sensing.
The medical importance of bacterial cell-to-cell communication became clear when scientists showed that the ability of some bacteria to cause diseases decreased when they interfered with quorum sensing. One example where the destruction signalling molecules led to a lower ability to cause disease was Staphylococcus aureus. This showed that bacterial cell-to-cell communication could be a potential target for new pharmaceuticals, and it soon became an area of intensive research, including my own. The hope is that if we better understand the mechanisms of quorum sensing, we will be able to develop new ways to fight bacterial infection. The first step is to identify and characterise the different systems used by different types of bacteria. I do this by looking for the signatures that signalling systems leave in the genome sequences and the networks of interaction between molecules in bacterial cells. This approach is often described as systems biology because I look at the interactions between lots of molecules rather than at one molecule at a time. This involves sifting through and integrating enormous amount of data, including more than 400 complete bacterial genomes.
Religious fundamentalists knew it all along: Darwinian evolution is dangerous. What they mean is that it is dangerous for our morals, when in fact it is dangerous for our physical health. That bacteria develop antibiotic resistance is sad proof that the theory of evolution is correct. To paraphrase Al Gore: 'Is it possible we should prepare for threats other than terrorism?' Antibiotic resistance is certainly among them.