Sunday, February 15, 2009
Bacteria and communication
Bacteria are simple, single-celled organisms, with a single strand of DNA. It's easy to assume that they couldn't possibly communicate. Bonnie Bassler, a professor of molecular biology at Princeton, begs to differ.
Her research has shown that bacteria can communicate, through 'quorum sensing', which assesses the density of bacteria in the neighbourhood.
She told a fascinating story of the complex symbiosis between noctural squid and bacteria which live in a cavity inside the squid. In the daytime, the squid flushes the bacteria. However, at night, as they return to the cavity, the bacteria 'sense a quorum' and being to luminesce. The squid has sensors on its back which sense the level of light above it. The squid opens the shutter on this cavity just enough to let out light to match the level of light above, so that the squid does not cast a shadow. What an astonishing, complex system to assist its hunting.
More relevant to humans is the fact that disease-causing bacteria release their toxins only when they 'sense a quorum'. So, if we could discover their method of communicating and interrupt it, we could prevent many diseases.
Bassler has done just that. Bacteria molecules are very similar, with the left hand side the same in all bacteria and the right hand side specific to each bacteria species. Enzymes which recognize the left hand side of the molecule thus constitute a 'universal Esperanto' for all bacteria, while an enzyme recognizing the right hand side represents an intra-species language.
Bassler's hope is to deepen understanding of this language and thus generate treatments for bacterial diseases, particularly relevant in a world where many kinds of bacteria have evolved to be resistant to current antibiotics.
Bassler ended her talk with a picture of the young researchers on her team, who actually do the hard slogging for these discoveries. She expressed her pleasure at working with such great students, particularly as they stay the same age as she gets older and older! A lovely sentiment to end a fascinating talk.