Princeton University
Department of Molecular Biology

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Tiger Talks


Tiny Conspiracies: Cell-to-Cell Communication in Bacteria

Tue, Oct 18, 2011
Location - TBA


Professor of Molecular Biology


On a warm fall evening, over 800 students, teachers and parents eagerly joined Professor Bonnie Bassler for her TIGER Talk on "Tiny Conspiracies: Cell-to-Cell Communication in Bacteria". Bonnie started by telling the audience that she was going to convince them that bacteria are multi-lingual. In the past, scientists thought that all a bacterium could do was eat, grow and divide. Bonnie graphically demonstrated out personal relationship with bacteria by pointing out that humans are composed of a trillion human cells, but have on them or in them 10 trillion bacterial cells. Even more amazing, when you add up the number of genes, a human is made up of 100 times as many bacterial genes as human. Our bacteria are not passive. They create an invisible layer of body armor, digest our food, make vitamins and educate our immune system. So she asked, "How do they do all these things if they act as individuals?"

Bonnie then showed a video of the bobtail squid burying itself in the sand to protect itself during the day. At night, when the squid comes out to eat, it can easily be seen by predators in the shallow water, so it uses a symbiotic relationship with a luminous bacteria Vibrio fischeri to protect itself. The squid grows the bacteria in a specialized light organ, which at night lights up and provides counter illumination to match starlight and moon light from above. The bacteria only produce light when they reach a high density. The bacterial cells are producing a molecule that diffuses into the environment. The receptor for this molecule is on the surface of the bacterial cells and senses the presence of this molecule. When the cell density is high, the concentration of these molecules is also very high and the activation of the receptors turns on hundreds of genes, one of which is light. This process is called quorum sensing. There is more than one system of communication and scientists have isolated species-specific signals and interspecies signals which tell bacteria who is out there. The interspecies signal for all bacteria tested is the same, a simple 5 carbon molecule. In pathogenic bacteria, signaling turns on virulence factors and production of biofilm genes. To develop novel approaches to new antibiotics, one could make it impossible for bacteria to listen or talk to each other. The search is on to discover molecules that jam the quorum sensing systems, but are not toxic to people. Bonnie outlined her search for these molecules and explained that there are a few promising leads, but it will be years before these are tested in humans. One additional exciting avenue of research is learning from bacteria themselves. How do bacteria outwit each other naturally? Can we use their strategies and develop new drugs to outwit pathogenic bacteria?



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